Class 9 Science Chapter 12: Patterns in Life: Diversity and Classification
- 5 topics
- 200 MCQs
- 40 short answers
- 20 long answers
- 110 flashcards
- 20 games
- ~230 min read
- English
Biodiversity, Hotspots and the Need for Classification
Life on Earth runs from microscopic algae to giant trees, and every one of those forms does some work that the rest depend on. India holds an unusual share of it. But a variety that large is unusable until it is sorted — which is what classification is for.
What you will be able to do
- Define biodiversity and give examples of the roles organisms play in an ecosystem.
- Explain what endemic species and biodiversity hotspots are, with Indian examples.
- Describe how the biodiversity we see today came about.
- List the criteria scientists use to classify living organisms.
- State what biological classification is and why it is needed.
Key points
The Earth carries an enormous variety of living things, from organisms too small for the eye to giant trees, from glowing jellyfish to soaring eagles.
They turn up in every sort of place, on snowbound mountain slopes as readily as on the reefs off the Andamans.
This immense variety of living organisms goes by the name of biodiversity.
It is essential for life on the Earth, since every organism plays some part in keeping nature stable and working.
The greater part of the air we take in is put out by tiny green things adrift in the sea.
Fungi and bacteria break down fallen leaves and turn waste into manure, which makes the soil fertile.
Flowers get their pollen carried by birds, by bees and by bats; the plants themselves take in sunlight and out of it make the food on which almost everything else lives.
These interconnections keep ecosystems going and make the Earth fit for living things.
People too depend on biodiversity for food, shelter, medicines and livelihoods.
For centuries farmers used their practical knowledge to conserve diverse crop varieties carrying useful characters, such as drought tolerance, pest resistance and the ability to grow in nutrient-poor soils.
They had worked out for themselves that a mixed field is a safer field, and that safety in the field is what keeps a household fed.
Across so wide a variety, organisms share certain similarities while also showing many differences.
To study that variety in an orderly way, scientists group and classify organisms by their shared characteristics and their evolutionary relationships.
Classification helps us see how organisms are related, how they work, and how the knowledge can be put to use in ecosystem management, biodiversity conservation and sustainable farming.
The country itself offers five kinds of ground at once: high mountains along the north, dry sand in the west, wet forest in the north-east, raised tableland through the south, and long shores on the seas to either side.
Each of these regions has its own soil types and its own climatic conditions of temperature and rainfall, and together these varied habitats support a wide variety of species.
Some species are restricted to particular regions of the world and occur naturally nowhere else, and such species are called endemic species.
The Nilgiri tahr, the lion-tailed macaque, the Indian pitcher plant Nepenthes khasiana and the Neelakurinji are found only in India.
Where a great many such restricted kinds occur together and a large part of their ground has already been destroyed, the area is spoken of as a biodiversity hotspot.
Such areas matter particularly for conservation, and the Western Ghats, Indo-Burma including North East India, the Himalayas, and Sundaland including the Nicobar Islands are among the global examples.
These areas are especially rich both in the number of organisms and in their variety.
Protecting them matters because they support food webs and help ecosystems stay healthy.
The biodiversity seen on the Earth today was not always what it is now.
Small differences between individuals affected their chances of surviving and reproducing, by helping them fit conditions that had changed.
Piling up across generation after generation, those unlikenesses at length amounted to kinds of living thing that had not existed before.
The diversity of today is therefore the outcome of continuous change across a vast span of time, shaped by the dealings between organisms and their surroundings.
Studying that biological diversity is made possible by the systematic framework which classification provides.
Older Indian practice knew a good deal about country and what lived in it: the Sangam scheme of Tinai landscapes and the setting aside of groves as sacred are two instances.
Those customs effectively preserved locally diverse habitats, in keeping with present-day ecological principles even though they were never set out as a formal ecological theory.
Grouping the animals of an ecosystem shows that the same organism can fall into different groups depending on the criterion chosen, whether that is where it is seen, when it is active or what it eats.
That raises the question of how scientists decide which features to use, and leads to classification, a systematic way of organising the Earth's living diversity.
Scientists commonly look first at broad and easily visible features and then at more detailed ones.
Under external features come the things a person can simply see: how big the organism is, what shape it takes, and how its body is put together.
Mode of nutrition means whether an organism is autotrophic or heterotrophic.
Internal structures cover skeletal patterns, the presence or absence of organs, and the different types of tissues.
Cell structure covers whether the organism is unicellular or multicellular, whether the cell is eukaryote or prokaryote, and whether a cell wall is present or absent.
Ecological role means whether the organism is a producer, a consumer or a decomposer.
Reproduction means whether asexual or sexual methods are used, or both.
Genetic similarity asks how closely the inherited material of one organism matches another's, a comparison now made directly on the DNA.
These features help us grasp how organisms resemble and differ from one another, and similar features suggest that the organisms have evolved from common ancestors.
Imagine walking into a huge library with thousands of books scattered over the floor, wanting one particular title such as Charles Darwin's On the Origin of Species.
Without books arranged by subject, author or section, finding any one of them would be hard, and the Earth's millions of organisms present the same problem.
At Pakke, a reserve in Arunachal Pradesh, close to three hundred kinds of bird have been listed — a remarkable share, given that the country as a whole musters about thirteen hundred.
Pakke is also known for supporting four species of hornbill: the Rufous-necked, the Oriental Pied, the Great and the Wreathed.
None of the four will nest except in an old tree carrying a hollow of the right size, and each wants fruits of its own kind, so the four end up in different quarters of the forest according to what grows where.
Studying such patterns lets scientists ask precise questions about how species are distributed within a forest and which plants and animals are closely linked.
Resemblances turn up at every level — in outward form, in the tissues and organs within, and in the way the cells themselves are arranged.
Variety on that scale is unmanageable unless it is sorted, so organisms are put into groups according to what they share and where they part; the discipline of doing so is biological classification.
It puts the study of living organisms on an orderly, systematic footing.
It helps us see how living beings resemble and differ from one another.
It shows how one kind stands to another, both in descent and in the dealings between them.
It helps in identifying and naming newly discovered organisms.
It serves conservation by picking out which kinds are sliding towards extinction.
It allows scientists all over the world to discuss organisms using one common system.
Full explanation
What Biodiversity Is
What lives on this planet runs from things too small for the eye to catch up to trees of immense size, and takes in jellyfish that give off light and eagles riding the air.
There is nowhere they are not — Himalayan snowfields, Andaman coral and everything between. Biodiversity is the word for that whole range.
Why it matters
Every organism has its part in keeping nature stable and working:
| Who | What they do |
|---|---|
| Algae too small to see, in the sea | Put out the greater part of the oxygen we breathe |
| Fungi and bacteria | Rot down fallen leaves; turn refuse into manure and so feed the soil |
| Birds, bees and bats | Pollinate flowers |
| Plants | Capture sunlight to prepare the food that supports nearly all life |
It is by such linkages that ecosystems keep going, and that this planet remains fit to live on at all.
And for us
Our own food, our shelter, our medicines and our work all rest on it. Farmers have kept a range of crop varieties going for hundreds of years, each for some property worth having:
- drought tolerance
- pest resistance
- willingness to grow on poor ground
They had grasped that a mixed planting is less likely to fail altogether, and that food is safer for it.
12.1 India as a Biodiversity Hotspot
India's natural landscape is itself diverse:
| Where | What |
|---|---|
| North | Mountains |
| West | Desert |
| North East | Rainforests |
| South | Plateaus |
| Coasts | Long shores on both the Arabian Sea and the Bay of Bengal |
No two of these share a soil or a climate, whether one measures warmth or rain; and where habitats differ that much, the species do too.
Endemic species
Species restricted to particular regions of the world and not found naturally anywhere else are called endemic species.
Found only in India:
- Nilgiri tahr
- Lion-tailed macaque
- Nepenthes khasiana — the Indian variety of the pitcher plant
- Neelakurinji
Hotspots
Where a region carries many species found nowhere else and has already lost much of its habitat, it is called a biodiversity hotspot.
Many found nowhere else, and much already lost — both halves are needed.
Global examples include:
- the Western Ghats
- the Indo-Burma region, North East India with it
- the Himalayas
- Sundaland, which takes in the Nicobars
These are especially rich in the number of organisms and in their diversity. They are worth guarding because food webs rest on them and ecosystems stay sound through them.
12.2 How Has the Biodiversity Evolved?
Life has not always looked as it looks now.
- Slight variations from one individual to the next told on whether they lived and whether they bred, since some of them suited altered conditions better than others.
- Those differences accumulated over many generations.
- Out of them came forms of life that had not existed before.
What we have now is the product of change going on without interruption across an immense stretch of time, worked out between organisms and the places they lived.
Studying it is made possible by the systematic framework that classification provides.
India's Scientific Contributions
The Tinai scheme of landscapes in the Sangam literature, and the long practice of leaving sacred groves untouched, both argue a considerable grasp of country and of what lives in it. Neither was ever set down as ecological theory, yet each kept local habitats varied, which is what ecology now recommends.
12.3 How to Classify Organisms?
Activity 12.1 — one ecosystem, many groupings
Looking at the animals of an ecosystem, you might record for each: where it is seen (flying high, flying near the ground, tree, water, forest floor), when it is active (day, night, unsure), and any visible features.
Sort them again on a fresh basis each time — carnivore: eagle, tiger, leopard, if you sort on diet.
Notice that one creature lands in a different group each time you change the basis you are sorting on.
Which raises the real question: how do scientists decide which features to use?
12.3.1 Criteria for Classifying Living Organisms
Scientists look at broad and easily visible features first, and then at more detailed ones.
| # | Criterion | What it covers |
|---|---|---|
| 1 | External features | Shape, size, how the body is put together |
| 2 | How it feeds | Makes its own food, or takes it |
| 3 | What is inside | Skeleton, if any; which organs are there; what tissues |
| 4 | Cell structure | Unicellular or multicellular; eukaryote or prokaryote; cell wall present or absent |
| 5 | Its part in the system | Produces, consumes, or breaks down |
| 6 | How it breeds | Asexually, sexually, or both |
| 7 | Genetic similarity | Similarities in inherited features, studied in detail using DNA |
Where two organisms are built alike, the likeliest reason is an ancestor they hold in common.
Alike now, related once.
12.4 The Need for Classification
Picture a very large library in which every book, and there are thousands, is lying about on the floor. The one you are after is Darwin's On the Origin of Species. Where would you begin?
Without books arranged into subjects, authors or sections, finding any one would be difficult. The Earth is home to millions of organisms, and the problem is the same.
Activity 12.2 — Pakke Tiger Reserve
In the Pakke Tiger Reserve, Arunachal Pradesh, scientists have recorded nearly 300 bird species — striking, when the whole of India has about 1,300.
Pakke supports four species of hornbill:
- Rufous-necked Hornbill
- Oriental Pied Hornbill
- Great Hornbill
- Wreathed Hornbill
Birds of that size will nest in nothing but an old tree of good girth with a hollow to suit them, and each kind wants particular fruit. So one part of the forest holds one hornbill and another part another, according to how big the trees are and what is in fruit.
Patterns like that let precise questions be put. Where in a forest does each species sit? Which plant goes with which animal? And what follows if the big old trees go?
Biological classification
Many organisms show similarities in external features, internal structure (tissues and organs) and cellular organisation. Grouping them by similarities and differences organises information, shows relationships, and lets life be studied systematically.
The discipline of sorting living things into such groups is biological classification.
What it does for us
- Makes the study of living organisms more organised and systematic.
- Helps us understand similarities and differences among living beings.
- Helps us understand how organisms are related and how they interact.
- Helps in identifying and naming newly discovered organisms.
- Supports biodiversity conservation by identifying organisms under threat of extinction.
- Allows scientists all over the world to discuss organisms using a common system.
Concepts and terms
The immense variety of living organisms, from the microscopic to the gigantic, across every habitat. Every organism plays a part in keeping nature stable and working.
A species restricted to a particular region of the world and found naturally nowhere else, such as the Nilgiri tahr or the Neelakurinji.
A region that both supports a large number of endemic species and has undergone significant habitat loss. Two conditions, not one.
External features, mode of nutrition, internal structures, cell structure, ecological role, reproduction and genetic similarity — the broad and visible first, the detailed after.
The scientific system of grouping living organisms by their similarities and differences, so that so vast a variety can be studied, related, named and conserved.
Did you know
The greater part of the air we take in is put out by tiny green things adrift in the sea.
Nearly 300 bird species have been recorded in the Pakke Tiger Reserve alone, out of about 1,300 for the whole of India.
The Tinai scheme of landscapes in the Sangam literature, and the practice of leaving sacred groves untouched, were keeping habitats varied long before anyone called the subject ecology.
Memory tricks
What makes a hotspot — Many found nowhere else, and much already lost — Endemism alone is not enough; habitat loss is the second half.
The order of looking — Broad and visible first, detailed after — Shape and size before tissues and DNA.
Why classify at all — A library with the books on the floor — Millions of organisms, and no way to find one.
What similarity suggests — Alike now, related once — Shared features point to common ancestors.
Practice MCQs with answers (40)
- A the total number of individual animals in one forest
- B the variety of habitats, but not of the organisms in them
- C the immense variety of living organisms on the Earth
- D the variety of crops that farmers choose to grow
Show answer
Why:
From the microscopic to the gigantic.
- A the giant trees of tropical forests
- B fungi and bacteria in the soil
- C birds, bees and bats as they fly
- D microscopic algae in the oceans
Show answer
Why:
Small organisms, large contribution.
- A pollinating flowers so that fruits and seeds can form
- B capturing sunlight to prepare food for other organisms
- C decomposing fallen leaves and turning waste into manure
- D releasing most of the oxygen that other organisms breathe
Show answer
Why:
Which is what makes the soil fertile.
- A It guarantees that every variety will give the same yield
- B It reduces the risk of crop failure and strengthens food security
- C It removes the need for any soil nutrients at all
- D It makes the crops easier to classify scientifically
Show answer
Why:
Farmers worked this out over centuries.
- A Rainforests in the west and desert in the North East
- B Mountains in the south and plateaus in the north
- C Rainforests in the North East and desert in the west
- D Coastlines only along the Bay of Bengal, not the Arabian Sea
Show answer
Why:
Mountains north, plateaus south, coasts on both seas.
- A is found on every continent of the world
- B is threatened with extinction in the near future
- C has been introduced into a region by human beings
- D is restricted to a region and found naturally nowhere else
Show answer
Why:
Restriction, not rarity, is the definition.
- A The Nilgiri tahr
- B The African elephant
- C The common house sparrow
- D The coconut palm
Show answer
Why:
So are the lion-tailed macaque and the Neelakurinji.
- A a variety of macaque found in the Western Ghats
- B a species of hornbill found at Pakke
- C the Indian variety of the pitcher plant
- D a flowering shrub of the Nicobar Islands
Show answer
Why:
One of four Indian endemics named.
- A Yes, because a large number of endemic species is enough
- B Yes, but only if it also lies within India
- C No, because hotspots are defined by area rather than species
- D No, because significant habitat loss is part of the definition
Show answer
Why:
Both conditions must hold.
- A The Western Ghats
- B The Gangetic plain
- C The Deccan plateau
- D The Thar desert
Show answer
Why:
Indo-Burma, the Himalayas and Sundaland are the others named.
- A North East India
- B the whole of the Himalayas
- C the Andaman coral reefs alone
- D the Nicobar Islands
Show answer
Why:
Indo-Burma is the one that includes North East India.
- A They contain no endemic species that could be lost
- B They support food webs and help ecosystems remain healthy
- C They are the only regions where classification is possible
- D They have suffered no habitat loss and need no protection
Show answer
Why:
Rich in number and in diversity alike.
- A It has been exactly the same since life first appeared
- B Small differences accumulated over many generations into new forms
- C New forms appeared all at once at a single point in time
- D Organisms deliberately changed themselves to suit conditions
Show answer
Why:
Continuous change over a vast span of time.
- A They made the individuals easier for scientists to classify
- B They caused the individuals to move to different habitats
- C They had no effect at all until humans began breeding them
- D They affected chances of survival and reproduction in changed conditions
Show answer
Why:
Then they accumulated across generations.
- A the first formal ecological theory ever written down
- B traditions that preserved locally diverse habitats
- C systems for naming newly discovered species
- D methods of increasing crop yields in ancient India
Show answer
Why:
They aligned with ecological principles without being stated as theory.
- A the same groups whatever criterion happens to be chosen
- B no useful groups at all, since animals resist grouping
- C groups that match the five kingdoms exactly
- D different groups depending on the criterion that is chosen
Show answer
Why:
Which raises the question of which criterion to use.
- A the DNA sequences of every organism
- B the tissues seen only under a microscope
- C broad and easily visible features
- D the ecological role each organism plays
Show answer
Why:
More detailed features come after.
- A Internal structures
- B Cell structure
- C External features
- D Ecological role
Show answer
Why:
The visible characteristics.
- A ecological role
- B external features
- C genetic similarity
- D mode of nutrition
Show answer
Why:
How the organism gets its food.
- A external features
- B cell structure
- C reproduction
- D internal structures
Show answer
Why:
What lies inside the body.
- A internal structures
- B cell structure
- C ecological role
- D mode of nutrition
Show answer
Why:
As is the presence or absence of a cell wall.
- A mode of nutrition
- B genetic similarity
- C ecological role
- D internal structures
Show answer
Why:
The part played in the ecosystem.
- A Genetic similarity
- B Ecological role
- C External features
- D Mode of nutrition
Show answer
Why:
Similarities in inherited features.
- A they must live in exactly the same habitat
- B they have the same mode of nutrition
- C they belong to the same kingdom by definition
- D they have evolved from common ancestors
Show answer
Why:
Which is why classification tracks relationship, not just looks.
- A Books are easier to classify than living organisms
- B Darwin's book is the most important one ever written
- C Without systematic arrangement, finding anything is difficult
- D Libraries should be organised by size rather than subject
Show answer
Why:
Millions of organisms pose the same problem.
- A Kerala
- B Manipur
- C Arunachal Pradesh
- D Rajasthan
Show answer
Why:
Nearly 300 bird species recorded there.
- A 300
- B 1,300
- C 13,000
- D 130
Show answer
Why:
Nearly a quarter of the country's birds in one forest.
- A The Malabar Grey Hornbill
- B The Great Hornbill
- C The Wreathed Hornbill
- D The Oriental Pied Hornbill
Show answer
Why:
The fourth is the Rufous-necked Hornbill.
- A They avoid one another out of straightforward hostility
- B They nest in large old trees and feed on particular fruits
- C They are active at different hours of the day and night
- D They need different soil types in which to build nests
Show answer
Why:
Tree size and fruit availability decide it.
- A The hornbills would lose the nesting cavities they depend on
- B The hornbills would simply nest in younger trees instead
- C Nothing, since the hornbills feed rather than nest in them
- D Fruit availability would rise across the whole forest
Show answer
Why:
They nest only in large old trees with suitable cavities.
- A the practice of giving every organism a Latin name
- B the study of how one species turns into another
- C the listing of all organisms found in one habitat
- D the scientific system of grouping living organisms
Show answer
Why:
Grouping by similarities and differences.
- A It guarantees that no species will ever become extinct
- B It helps in identifying and naming newly discovered organisms
- C It lets scientists worldwide use one common system
- D It supports conservation by identifying threatened organisms
Show answer
Why:
Classification identifies threat; it does not remove it.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Endemic means restricted in range, not necessarily at risk.
- A 1 and 3 only
- B 1 and 2 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Autotrophic or heterotrophic belongs to mode of nutrition.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
The group depends on the criterion chosen.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
Endemism and habitat loss are both required, which is why species richness alone is not enough. The assertion stands, the reason is false.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
A common system lets scientists everywhere discuss the same thing.
- A Habitat, all three living in the same place
- B Eating habits, all three being carnivores
- C Time of activity, all three being nocturnal
- D Body covering, all three having feathers
Show answer
Why:
A different criterion would give a different group.
- A Only its colour and the depth of water it was found in
- B Whether it is unicellular, how it feeds, and whether it has a cell wall
- C Only the time of day at which it was collected
- D Only the name the local people give to the pond
Show answer
Why:
Cell structure, nutrition and organisation are the fundamentals.
- A Reproduction — whether the organism is a producer or a consumer
- B Reproduction — whether the organism reproduces asexually, sexually or both
- C External features — whether the cell has a membrane-bound nucleus
- D Cell structure — whether the organism has a skeleton of any kind
Show answer
Why:
Producer and consumer belong to ecological role.
Important short questions (8)
Biodiversity is the immense variety of living organisms, from those invisible to the naked eye to giant trees, across every sort of habitat. It is essential because every organism plays a part in keeping nature stable and working: ocean algae release the greater part of the oxygen we breathe, fungi and bacteria decompose leaves and make the soil fertile, birds, bees and bats pollinate flowers. Plants capture sunlight to make the food nearly all other life depends on. These interconnections sustain ecosystems.
Endemic species are those restricted to particular regions of the world and found naturally nowhere else, such as the Nilgiri tahr, the lion-tailed macaque, Nepenthes khasiana and the Neelakurinji, all of which occur only in India. A biodiversity hotspot is a region that carries many species found nowhere else and has already lost much of its habitat. The Western Ghats, Indo-Burma including North East India, the Himalayas, and Sundaland including the Nicobar Islands are examples.
The country's own ground is varied. There is mountain in the north, desert in the west, rainforest in the North East and plateau in the south. Long shores run along both the Arabian Sea and the Bay of Bengal. Each region has its own soil types and its own conditions of temperature and rainfall, and these varied habitats together support a wide variety of species.
Small differences between individuals affected their chances of surviving and reproducing, by helping them fit conditions that had changed. Those differences piled up generation on generation until forms of life existed that had not before. What we have now, then, is the product of change going on without interruption across an immense stretch of time, worked out between organisms and the places they lived.
The criteria include external features such as shape, size and body organisation. They include the mode of nutrition, whether autotrophic or heterotrophic. They include internal structures such as skeletal patterns, organs and tissue types, and cell structure, whether unicellular or multicellular and prokaryote or eukaryote. The presence of a cell wall; ecological role as producer, consumer or decomposer; reproduction, asexual or sexual or both; and genetic similarity, studied in detail using DNA.
Pakke carries close to 300 of the roughly 1,300 bird species India has, four of them hornbills, which will nest in nothing but an old tree of good girth with a hollow to suit them and which want particular fruit. Because of this, each species occupies a different part of the forest according to tree size and fruit availability. Telling the four apart is what lets scientists ask precise questions about how species are distributed and which plants and animals are closely linked.
It is the scientific way of sorting living things into groups by what they share and where they differ. It puts their study in order, so that what is known can be found again; it brings out resemblance and difference between kinds; and it shows how one kind stands to another, both in descent and in their dealings.
Because it allows scientists everywhere to discuss organisms using one and the same system, rather than local names and local groupings. It also helps in identifying and naming newly discovered organisms, and supports biodiversity conservation by identifying the organisms that are under threat of extinction.
Long answer questions (4)
Biodiversity is the immense variety of living organisms on the Earth. It runs from organisms too small for the naked eye to giant trees, and from glowing jellyfish to soaring eagles, occupying habitats as unlike each other as the snow-clad Himalayas and the coral reefs of the Andaman Sea.
It is essential for life, because every organism plays a part in keeping nature stable and working. Algae too small to see put out the greater part of the oxygen we breathe. Fungi and bacteria rot down fallen leaves and turn refuse into manure, and so feed the soil. Birds, bees and bats pollinate flowers. Plants capture sunlight to prepare the food that nearly all other life depends on. These interconnections sustain ecosystems and make the Earth fit to live on.
People depend on it too, for food, shelter, medicines and livelihoods. Farmers conserved diverse crop varieties carrying drought tolerance, pest resistance and the ability to grow in poor soils, having realised that diversity reduces the risk of crop failure.
India holds so much of it because the country's own ground is varied: mountain in the north, desert in the west, rainforest in the North East, plateau in the south, and long shores on both seas. Each region carries its own soils and its own temperature and rainfall, and together they support a wide variety of species.
Some species are restricted to particular regions of the world and occur naturally nowhere else. Such species are called endemic species. Four are named as found only in India: the Nilgiri tahr, the lion-tailed macaque, the Indian pitcher plant Nepenthes khasiana, and the Neelakurinji.
A biodiversity hotspot is more narrowly defined. It is a region that supports a large number of endemic species and that has also undergone significant habitat loss. Both conditions are needed. A region rich in endemic species but untouched is not a hotspot; nor is a badly damaged region with nothing peculiar to it.
Global examples include the Western Ghats, Indo-Burma including North East India, the Himalayas, and Sundaland including the Nicobar Islands.
They deserve protection on two counts. They are especially rich, both in the number of organisms and in the diversity of those organisms, so a great deal is concentrated in a small area. And they support food webs and help ecosystems remain healthy, so what is lost there is not lost only there.
The damage already suffered is precisely why they are urgent. A hotspot is by definition a place where a great deal is at stake and a great deal has already gone.
Scientists look first at broad and easily visible features, and then at more detailed ones. Seven criteria are used.
External features are the visible characteristics: shape, size and body organisation. Mode of nutrition is whether the organism is autotrophic or heterotrophic. Internal structures cover skeletal patterns, the presence or absence of organs, and the types of tissues. Cell structure covers whether the organism is unicellular or multicellular, whether the cell is prokaryote or eukaryote, and whether a cell wall is present. Ecological role is whether the organism is a producer, a consumer or a decomposer. Reproduction is whether asexual or sexual methods are used, or both. Genetic similarity means similarity in inherited features, which scientists study in detail using DNA.
More than one criterion is needed because any single one is arbitrary. Grouping the same set of animals by where they are seen, by when they are active and by what they eat gives three different sets of groups, and the same organism falls into different boxes each time.
What settles the matter is that similar features suggest evolution from common ancestors. Classification is meant to track relationship, and several lines of evidence together point to relationship more reliably than any one.
The case is made with an image. Imagine walking into a huge library where thousands of books lie scattered over the floor, and you want one particular title, say Charles Darwin's On the Origin of Species. Without arrangement by subject, author or section, finding any book at all would be difficult. The Earth holds millions of organisms, and the difficulty is the same.
Many organisms show similarities in external features, in internal structure such as tissues and organs, and in cellular organisation. Grouping them by such similarities and differences is what biological classification is.
It earns its place six times over. It puts the study of living organisms on an orderly, systematic footing. It helps us see how living beings resemble and differ from one another. It helps us understand how organisms are related to one another and how they interact. It helps in identifying and naming newly discovered organisms. It supports biodiversity conservation by identifying the organisms under threat of extinction. And it allows scientists all over the world to discuss organisms using one common system.
The Pakke hornbills show the point at work: only by telling four similar birds apart can scientists ask how species are distributed in a forest, and what would follow if the old trees went.
Flashcards (22)
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- Unscramble: Places and Ideas
Classification Systems Over Time: Monera and Protista
Two kingdoms, then three, then four, then five. Each time an organism turned up that would not fit — an amoeba that moves but is one cell, a bacterium with no proper nucleus, a mushroom that neither moves nor makes its own food — the system had to be rebuilt around it.
What you will be able to do
- Trace the classification systems from Aristotle to Whittaker and say who proposed each.
- Explain what forced the addition of Protista, Monera and Fungi in turn.
- State the four criteria on which the five kingdom classification rests.
- Describe Kingdom Monera and the place of bacteria and cyanobacteria.
- Describe Kingdom Protista and the roles protists play.
Key points
Scientists have built different classification systems over time, each on the knowledge that was available to them.
Aristotle, around the 4th century BCE, sorted animals by where they lived, on land, in water or in the air, and also by how they looked.
The weakness of that scheme was that it leaned almost wholly on outward characters that anyone could see at a glance.
In the 18th century a two kingdom system was introduced, and every living thing was put into either Plantae or Animalia.
Plantae held the organisms that stay in one place and make their own food.
Animalia held the organisms that move about and depend on other organisms for their food.
The scheme soon caused trouble, because Amoeba, Paramecium and bacteria would not sit comfortably in either box.
Amoeba and Paramecium move about as animals do, yet each is a single cell and takes its food from elsewhere, whereas plants and animals alike are made of many cells.
To meet this, a third kingdom, Protista, was added for the unicellular microscopic organisms.
As microscopes grew better, a further difference showed itself: an amoeba has a true nucleus bounded by a membrane, and bacteria have none.
Since the two are alike in being single-celled but unlike in that fundamental way, bacteria were given a kingdom of their own, Monera.
That produced a four kingdom system of Plantae, Animalia, Protista and Monera, with Protista holding mostly unicellular organisms that have a true nucleus.
Later still it was noticed that fungi such as mushrooms stay put as plants do, yet feed as animals do, taking in nutrients by absorption.
Many of them absorb from dead and decaying matter, though some live in partnership with other organisms and some as parasites, and for this reason fungi were placed in a kingdom of their own.
The result was the five kingdom classification, made up of Monera, Protista, Fungi, Plantae and Animalia.
The timeline of these schemes runs from the artificial system of Aristotle in the 4th century BCE, which grouped animals by land, water and air.
In 1758 Carolus Linnaeus divided life into Plantae and Animalia, the two kingdom system.
In 1866 Ernst Haeckel added Protista for microscopic life, making three kingdoms.
In 1938 Herbert F. Copeland arrived at four kingdoms, Monera, Protista, Plantae and Animalia.
In 1969 Robert H. Whittaker grouped life into five kingdoms, Monera, Protista, Fungi, Plantae and Animalia.
The Rigveda and the Brihat Samhita classify animals by their habitat, whether of the land, the water or the air, and also by their behaviour patterns and their ecological roles.
In the five kingdom classification all life forms are grouped on certain common features.
Cell type asks whether the organism is a prokaryote or a eukaryote.
Cell structure asks whether a cell wall is present or absent.
Level of organisation asks whether the organism is unicellular or multicellular.
Mode of nutrition asks whether it is autotrophic or heterotrophic.
The concept map adds ecological role, so that Plantae are the producers, Animalia the consumers and Fungi the decomposers.
Where a cell wall is present, its material tells the kingdom apart: chitin in the fungi and cellulose in the plants, while animals have no cell wall at all.
Monera covers bacteria, archaea and cyanobacteria, whose nucleus is primitive and not bounded by a membrane, and which may or may not carry a cell wall.
Bacteria and cyanobacteria are single-celled prokaryotes grouped under Monera.
Bacteria are found everywhere, in soil, water and air, in hot springs and other extreme places where most organisms could not survive, and even inside human bodies.
The stomachs of cud-chewing cattle hold them too, and it is their work that turns the dung of such animals into a burnable gas.
Some bacteria are harmful and cause disease, being called pathogens, but many are useful, such as Lactobacillus and Rhizobium.
Cyanobacteria are autotrophs and decomposers, and besides nutrient cycling, some bacteria break down pollutants such as oil, pesticides and sewage.
Ram Bux Singh is widely called the Father of Modern Biogas, a pioneering Indian scientist who worked on biogas technology.
The country's first plant built on a proper design went up under him in 1957 at Ramnagar in Sitapur district of Uttar Pradesh, and from it dates the systematic study of the subject in India.
He went on to develop low-cost, efficient biogas plants for rural areas, served as an international consultant, and helped set up plants in several countries.
Between them, his efforts advanced three things at once: energy that renews itself, refuse turned to account, and development that can be kept up.
The blue-green kinds, cyanobacteria, were among the earliest living things anywhere to give off oxygen while making their food from light.
About 2.5 billion years ago that oxygen accumulated in the atmosphere and made the Earth suitable for other forms of life.
Their fossils turn up in layered structures called stromatolites, which occur in Rajasthan and in Madhya Pradesh, and little older evidence of life exists anywhere.
All single-celled eukaryotes that either have no cell wall, or have one made of cellulose, are grouped under the kingdom Protista.
They are microscopic and highly diverse organisms, Amoeba, Euglena, Paramecium and Chlamydomonas among them.
Protists can be studied by making a hay infusion, for which a small sample of mown grass, straw or fodder is collected.
A small glass bottle is filled one fourth with that plant material, then filled up with stagnant or pond water and mixed.
The bottle is covered with muslin cloth tied on with thread and left undisturbed for a week.
The cloth is then opened just enough to admit a dropper, a drop of the water is taken, placed on a clean slide, and observed under a microscope.
The infusion may smell bad, so a lab coat, mask and gloves are worn, and it is discarded after autoclaving.
What the kingdom holds are one-celled organisms of the nucleated sort, at home in water or wherever the ground stays damp.
Some protists are autotrophic and others are heterotrophic.
In the food chains of ponds and seas they matter a great deal: a part of them give off oxygen, and a part are themselves eaten by small creatures.
Some protists function as decomposers and so help in nutrient cycling.
Full explanation
12.5 Classification Systems Over Time
Scientists have developed different classification systems over time, each based on the knowledge available then.
Aristotle, 4th century BCE
He grouped animals by habitat — land, water and air — and also by external appearance.
The limitation: it relied mainly on easily observable external characteristics.
The two kingdom system, 18th century
| Kingdom | Defined as |
|---|---|
| Plantae | Organisms that do not move from place to place and synthesise their own food |
| Animalia | Organisms that move from place to place and depend on other organisms for food |
The organism that broke it
What is to be done with Amoeba, with Paramecium, with bacteria?
The first two get about as animals do and take their food as animals do, but each is a single cell — whereas plants and animals alike are built of many.
The fix: a third kingdom, Protista, for unicellular microscopic organisms.
The next problem: better microscopes
An amoeba has a true nucleus (membrane-bound). Bacteria do not.
Both are unicellular, but that difference is fundamental. So bacteria were placed in a separate kingdom, Monera.
Four kingdoms: Plantae, Animalia, Protista, Monera. Protista now holds mostly unicellular organisms with a true nucleus.
The last addition: fungi
Fungi such as mushrooms do not move, like plants — but are heterotrophic. They obtain nutrients by absorption:
- many from dead and decaying matter
- some symbiotic
- some parasitic
So fungi got a kingdom of their own, giving the five kingdom classification.
Amoeba, then bacteria, then mushrooms — one awkward organism at a time.
The timeline (Fig. 12.4)
| When | Who | System |
|---|---|---|
| 4th century BCE | Aristotle | Artificial system — animals by habitat: land, water, air |
| 1758 | Carolus Linnaeus | Two kingdom — Plantae, Animalia |
| 1866 | Ernst Haeckel | Three kingdom — added Protista for microscopic life |
| 1938 | Herbert F. Copeland | Four kingdom — Monera, Protista, Plantae, Animalia |
| 1969 | Robert H. Whittaker | Five kingdom — Monera, Protista, Fungi, Plantae, Animalia |
Classification in early Indian texts
Animals are sorted in the Rigveda and the Brihat Samhita by where they live (on land, in water or in the air), by how they behave, and by the part they play in their surroundings.
12.6 The Five Kingdom Classification
The criteria (Activity 12.3)
| Criterion | The two possibilities |
|---|---|
| Cell type | Prokaryote or eukaryote |
| Cell structure | Cell wall present or absent |
| Level of organisation | Unicellular or multicellular |
| Mode of nutrition | Autotrophic or heterotrophic |
The concept map adds ecological role: Plantae are producers, Animalia consumers, Fungi decomposers.
Where the cell wall tells you the kingdom
| Kingdom | Cell wall |
|---|---|
| Fungi | Present, of chitin |
| Plantae | Present, of cellulose |
| Animalia | Absent |
| Monera | May or may not be present |
| Protista | Absent, or of cellulose |
Chitin for fungi, cellulose for plants, none for animals.
12.6.1 Kingdom Monera — Unicellular Prokaryotes
Bacteria and cyanobacteria are single-celled prokaryotes grouped under Monera.
Monera also takes in the archaea. The nucleus is primitive — not bounded by a membrane — and a cell wall may or may not be present.
Where bacteria are found
- in the ground, in water, in the air
- in hot springs and other places so harsh that almost nothing else holds on
- inside human bodies
- in the gut of ruminants, where they are responsible for the production of biogas from dung
Harmful and useful
| Harmful | Pathogens, which cause diseases |
| Useful | Lactobacillus, Rhizobium |
| Cyanobacteria | Autotrophs and decomposers |
| Some bacteria | Break down pollutants — oil, pesticides, sewage |
Bridging Science and Society — Ram Bux Singh
Known as the 'Father of Modern Biogas'. The country's first properly engineered biogas plant was his, put up at Ramnagar in Sitapur, Uttar Pradesh, in 1957; organised research on biogas in India begins there. Afterwards he designed plants that villages could afford and that worked well, advised abroad, and had a hand in installations in a number of countries — all of it for renewable energy, for dealing with waste, and for development that lasts.
Threads of Curiosity — the first oxygen
The blue-green algae, or cyanobacteria, were among the earliest things to put out oxygen by photosynthesis.
Oxygen built up in the air from around 2.5 billion years back, and only then did the planet become habitable for much else.
Their fossils turn up in layered structures called stromatolites, which occur in Rajasthan and in Madhya Pradesh. Little older evidence of life exists anywhere.
12.6.2 Kingdom Protista — Unicellular Eukaryotes
Protista takes in every eukaryote of a single cell that either has no wall at all or has one built of cellulose.
They are microscopic and highly diverse: Amoeba, Euglena, Paramecium, Chlamydomonas.
Activity 12.5 — a hay infusion
- Take a little cut grass from a mown lawn, or some straw, or fodder.
- Fill one fourth of a small glass bottle with it.
- Fill the bottle with stagnant or pond water and mix.
- Cover with muslin cloth, tied with thread.
- Leave undisturbed for a week.
- Open just enough to insert a dropper; take a drop.
- Place it on a clean slide and observe under a microscope.
Caution: the infusion may smell bad. Wear a lab coat, mask and gloves, and discard after autoclaving.
What protists do
- They live in water or moist places.
- Some are autotrophic, others heterotrophic.
- They form an important link in aquatic food chains: some produce oxygen, others serve as food for small animals.
- Some function as decomposers and help in nutrient cycling.
Concepts and terms
Each new system answered an organism the old one could not place: Amoeba for Protista, bacteria for Monera, mushrooms for Fungi.
Cell type (prokaryote or eukaryote), cell structure (cell wall present or absent), level of organisation (unicellular or multicellular) and mode of nutrition (autotrophic or heterotrophic).
Unicellular prokaryotes — bacteria, archaea and cyanobacteria. The nucleus is primitive and not membrane-bound; a cell wall may or may not be present.
Single-celled eukaryotes with no cell wall, or one of cellulose. Microscopic, highly diverse, living in water or moist places, some autotrophic and some heterotrophic.
Structures holding fossils of ancient cyanobacteria, found in Rajasthan and Madhya Pradesh. Some of the earliest evidence of life on the Earth.
Did you know
Cyanobacteria were among the first organisms to make oxygen by photosynthesis, and about 2.5 billion years ago that oxygen built up in the atmosphere.
Stromatolites holding fossils of ancient cyanobacteria have been found in Rajasthan and Madhya Pradesh.
India's first scientifically designed biogas plant was set up in 1957 at Ramnagar, Sitapur, in Uttar Pradesh.
Memory tricks
The five kingdoms — Monera, Protista, Fungi, Plantae, Animalia — In that order: simplest cell first, most complex last.
What broke each system — Amoeba, then bacteria, then mushrooms — One awkward organism at a time.
Cell wall material — Chitin for fungi, cellulose for plants, none for animals — The wall tells you the kingdom.
Monera against Protista — No true nucleus, or a true one — Both single-celled; that is the dividing line.
Practice MCQs with answers (40)
- A the presence or absence of a true nucleus
- B their habitat, as of land, water or air
- C whether they were unicellular or multicellular
- D the material of which their cell walls were made
Show answer
Why:
And also by external appearance.
- A It relied entirely on the internal structure of the cell
- B It placed plants and animals in the same single group
- C It required microscopes that did not yet exist
- D It relied mainly on easily observable external characteristics
Show answer
Why:
Appearance does not track relationship.
- A move from place to place and make their own food
- B do not move and depend on others for their food
- C are single-celled and have no true nucleus
- D do not move from place to place and make their own food
Show answer
Why:
Animalia were the opposite on both counts.
- A It moves like an animal but is unicellular and heterotrophic
- B It stays fixed like a plant but is heterotrophic
- C It is multicellular but has no true nucleus at all
- D It makes its own food but also moves about freely
Show answer
Why:
Plants and animals are both multicellular.
- A multicellular organisms that absorb their food
- B organisms without any true nucleus at all
- C unicellular microscopic organisms
- D organisms with cell walls made of chitin
Show answer
Why:
Amoeba and Paramecium were the awkward cases.
- A An amoeba has a true nucleus; bacteria do not
- B Bacteria have a true nucleus; an amoeba does not
- C Both amoeba and bacteria are multicellular
- D Both amoeba and bacteria make their own food
Show answer
Why:
Both are unicellular, but very different.
- A Plantae, Animalia, Protista and Fungi
- B Monera, Protista, Fungi and Plantae
- C Monera, Protista, Fungi and Animalia
- D Plantae, Animalia, Protista and Monera
Show answer
Why:
Fungi came last of the five.
- A move about like animals but make their own food by photosynthesis
- B do not move like plants but are heterotrophic, absorbing nutrients
- C are always unicellular and have no true nucleus
- D have cell walls made of cellulose, as plants do
Show answer
Why:
Staying put was never the issue; feeding was.
- A Dead and decaying matter, though some are symbiotic or parasitic
- B Sunlight, which they convert into food by photosynthesis
- C The soil directly, through roots like those of plants
- D Living animals only, never from anything already dead
Show answer
Why:
Absorption is the mode.
- A Herbert F. Copeland, in 1938
- B Ernst Haeckel, in 1866
- C Robert H. Whittaker, in 1969
- D Carolus Linnaeus, in 1758
Show answer
Why:
Copeland's was the four kingdom system.
- A Ernst Haeckel, in 1866
- B Aristotle, in the 4th century BCE
- C Robert H. Whittaker, in 1969
- D Carolus Linnaeus, in 1758
Show answer
Why:
Haeckel added the third kingdom.
- A add Monera for bacteria, making four kingdoms
- B add Fungi as a separate kingdom, making five
- C divide all life into Plantae and Animalia
- D add Protista for microscopic life, making three kingdoms
Show answer
Why:
Copeland's four came in 1938.
- A the presence or absence of a cell wall
- B habitat, behaviour patterns and ecological roles
- C whether they are prokaryotes or eukaryotes
- D the number of cells in their bodies
Show answer
Why:
Terrestrial, aquatic and aerial, among other grounds.
- A Whether the organism lives on land or in water
- B Whether the organism reproduces in the monsoon
- C Whether the organism is large or small in size
- D Whether the organism is a prokaryote or a eukaryote
Show answer
Why:
Cell type, cell structure, level of organisation, mode of nutrition.
- A Plantae
- B Animalia
- C Monera
- D Fungi
Show answer
Why:
Plantae are producers and Animalia consumers.
- A chitin
- B cellulose
- C calcium carbonate
- D nothing; it has no wall
Show answer
Why:
Plant cell walls are of cellulose.
- A Plantae
- B Fungi
- C Animalia
- D Monera
Show answer
Why:
Monera may or may not have one.
- A amoeba, euglena and paramecium
- B bacteria, archaea and cyanobacteria
- C yeast, mushrooms and Aspergillus
- D mosses, ferns and pines
Show answer
Why:
The second list belongs to Protista.
- A true, and bounded by a membrane
- B absent entirely, with no genetic material at all
- C primitive, and not bounded by a membrane
- D double, with two membranes around it
Show answer
Why:
That is what makes it a prokaryote.
- A Only in soil that has been freshly manured
- B Hot springs and other extreme environments
- C Only inside the bodies of larger animals
- D Nowhere outside a laboratory culture
Show answer
Why:
Also in soil, water, air and human bodies.
- A the digestion of proteins in the human stomach
- B the production of biogas from the dung of those animals
- C the breakdown of oil spills in the sea
- D the fixing of nitrogen in the roots of legumes
Show answer
Why:
Which is what a biogas plant exploits.
- A harmful bacteria, or pathogens
- B single-celled protists
- C unicellular fungi
- D useful bacteria
Show answer
Why:
Pathogens are the harmful ones.
- A autotrophs and decomposers
- B heterotrophs and consumers only
- C parasites of other bacteria
- D eukaryotes with a true nucleus
Show answer
Why:
They belong to Monera all the same.
- A the cell walls of plants and of fungi
- B pollutants such as oil, pesticides and sewage
- C rocks into the minerals that plants need
- D the oxygen in the atmosphere into ozone
Show answer
Why:
Besides their part in nutrient cycling.
- A in 1969, at Ramnagar, Sitapur, Uttar Pradesh
- B in 1957, at Ramnagar, Sitapur, Uttar Pradesh
- C in 1957, at Ramnagar, in Madhya Pradesh
- D in 1938, at Sitapur, in Rajasthan
Show answer
Why:
He is called the Father of Modern Biogas.
- A Oxygen from cyanobacteria accumulated and made the Earth fit for other life
- B The first five kingdom classification was proposed then
- C The earliest fungi appeared and began to decompose matter
- D The first multicellular animals developed a notochord
Show answer
Why:
Cyanobacteria were among the first to make oxygen.
- A the cell walls that surround cyanobacteria
- B the chambers in which protists are cultured
- C structures in which fossils of ancient cyanobacteria are found
- D the extreme environments in which bacteria live
Show answer
Why:
Found in Rajasthan and Madhya Pradesh.
- A Single-celled prokaryotes with a primitive nucleus
- B Single-celled eukaryotes without a cell wall, or with one of cellulose
- C Multicellular eukaryotes with cell walls of chitin
- D Multicellular autotrophs with cell walls of cellulose
Show answer
Why:
The second describes Monera.
- A Rhizobium
- B Aspergillus
- C Spirogyra
- D Paramecium
Show answer
Why:
Amoeba, Euglena and Chlamydomonas are the others named.
- A One half
- B Three fourths
- C One fourth
- D The whole of it
Show answer
Why:
The rest is stagnant or pond water.
- A undisturbed for a single day
- B in direct sunlight for a month
- C undisturbed for a week
- D in a refrigerator for three days
Show answer
Why:
Then a drop is taken with a dropper.
- A Lab coat, mask and gloves, and discarding after autoclaving
- B Working in the open air without any protective clothing
- C Pouring the infusion down a sink when finished with it
- D Tasting a drop to check that fermentation has occurred
Show answer
Why:
The infusion may smell bad.
- A all of them are autotrophs and none are ever eaten
- B all of them are heterotrophs and none produce oxygen
- C they alone can break down the cell walls of plants
- D some give out oxygen while others feed the smaller animals there
Show answer
Why:
Some also act as decomposers in nutrient cycling.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Both kingdoms are of single cells.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
1866 and three kingdoms belong to Haeckel.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
A protist may have no cell wall at all.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
Both are true. The shape of the hierarchy does not explain why the systems themselves kept being replaced.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
The fungal wall material is chitin; cellulose belongs to plants. The assertion holds, the reason is false.
- A Monera, being a single-celled prokaryote
- B Fungi, since its cell wall would be of chitin
- C Protista, being a single-celled eukaryote
- D Animalia, since it moves by means of cilia
Show answer
Why:
The true nucleus rules out Monera.
- A No problem would arise; being single-celled is grouping enough
- B Multicellular organisms would then have nowhere to be placed
- C Prokaryotes and eukaryotes would be grouped together despite a fundamental difference
- D The number of kingdoms would rise rather than fall
Show answer
Why:
That difference is precisely why Monera was separated.
Important short questions (8)
Around the 4th century BCE Aristotle grouped animals by their habitat, as of the land, the water or the air, and also by their external appearances. The limitation was that the system relied mainly on easily observable external characteristics, which do not reliably show how organisms are related.
Into Plantae went whatever stayed put and made its own food; into Animalia whatever went about and lived off other organisms. It failed because Amoeba, Paramecium and bacteria would not fit: Amoeba and Paramecium move about as animals do, yet are unicellular and heterotrophic, whereas plants and animals are multicellular.
First a third kingdom, Protista, was added to hold the unicellular microscopic organisms that fitted neither Plantae nor Animalia. Then improved microscopes showed that an amoeba has a true, membrane-bound nucleus while bacteria have none. Since both are unicellular but so unlike in that respect, bacteria were placed in a separate kingdom, Monera. That gave Plantae, Animalia, Protista and Monera.
Fungi such as mushrooms do not move about, as plants do not, yet they are heterotrophic: they obtain nutrients by absorption, many of them from dead and decaying matter, while some are symbiotic and some parasitic. Being neither self-feeding like plants nor mobile like animals, they needed a kingdom of their own, and that produced the five kingdom classification.
Cell type asks whether the organism is a prokaryote or a eukaryote. Cell structure asks whether a cell wall is present or absent. Level of organisation asks whether the organism is unicellular or multicellular. Mode of nutrition asks whether it is autotrophic or heterotrophic. The concept map adds ecological role, making Plantae producers, Animalia consumers and Fungi decomposers.
Monera covers bacteria, archaea and cyanobacteria: unicellular prokaryotes whose nucleus is primitive and not membrane-bound, and which may or may not carry a cell wall. Bacteria occur in soil, water, air, hot springs and inside bodies, and those in the gut of ruminants produce biogas from dung. Some are pathogens, but many are useful, such as Lactobacillus and Rhizobium, and some break down oil, pesticides and sewage.
Cyanobacteria were among the earliest living things anywhere to give off oxygen while making their food from light, and roughly two. A half billion years back enough of it had gathered in the air to make the planet habitable for other kinds of life. Their fossils sit in structures called stromatolites, found in Rajasthan and Madhya Pradesh, which count among the oldest traces of life anywhere on the planet.
It holds all single-celled eukaryotes that have no cell wall, or one made of cellulose. They are microscopic and highly diverse, living in water or moist places, some autotrophic and others heterotrophic. They form an important link in aquatic food chains, some producing oxygen and others serving as food for small animals, while some act as decomposers and help in nutrient cycling.
Long answer questions (4)
Aristotle, around the 4th century BCE, grouped animals by habitat, as of the land, the water or the air, and by their outward appearance. The scheme leaned almost wholly on characters anyone could see, and appearance is a poor guide to relationship.
In 1758 Linnaeus gave the two kingdom system. Plantae did not move and made their own food; Animalia moved and fed on others. The difficulty came from Amoeba and Paramecium, which move as animals do yet are single cells and heterotrophic, while plants and animals are both multicellular. Haeckel therefore added Protista in 1866 for unicellular microscopic organisms.
Better microscopes brought the next problem. An amoeba has a true, membrane-bound nucleus; bacteria have none. Both being single-celled but so unlike in that, Copeland in 1938 gave bacteria a kingdom of their own, Monera, making four.
The last change concerned the fungi. Mushrooms stay put as plants do, but feed by absorption, many from dead and decaying matter. In 1969 Whittaker gave them a separate kingdom, producing the five that we use: Monera, Protista, Fungi, Plantae and Animalia.
Each change followed the same pattern: an organism that would not fit, and a system rebuilt around it.
Four criteria carry the system. Cell type asks whether the organism is a prokaryote or a eukaryote. Cell structure asks whether a cell wall is present or absent. Level of organisation asks whether it is unicellular or multicellular. Mode of nutrition asks whether it is autotrophic or heterotrophic. The concept map adds a fifth consideration, ecological role.
On cell type, Monera alone are prokaryotes; the other four kingdoms are eukaryotes. On level of organisation, Monera and Protista are unicellular, while Fungi, Plantae and Animalia are multicellular, yeast being an exception among the fungi.
On cell structure, the material of the wall is itself diagnostic: chitin in the fungi, cellulose in the plants, no wall at all in the animals. A moneran may or may not have one, and a protist has either none or one of cellulose.
On nutrition, Plantae are autotrophic, performing photosynthesis, while Fungi and Animalia are heterotrophic, the fungi absorbing and the animals ingesting. Monera and Protista include both kinds.
On ecological role, Plantae are the producers, Animalia the consumers and Fungi the decomposers.
Monera covers bacteria, archaea and cyanobacteria, all of them unicellular prokaryotes. Their nucleus is primitive, not bounded by a membrane, and a cell wall may or may not be present. It was this absence of a true nucleus, seen once microscopes improved, that separated them from the single-celled eukaryotes of Protista.
Bacteria are found everywhere: in soil, water and air, in hot springs and other extreme environments where most organisms could not survive, and even inside human bodies. They also inhabit the stomachs of cattle and their kin, and it is their work that turns the dung into biogas.
Some are harmful and cause disease, and are called pathogens. Many are useful, Lactobacillus and Rhizobium among them. Cyanobacteria are autotrophs and decomposers, and beyond nutrient cycling some bacteria break down pollutants such as oil, pesticides and sewage.
Cyanobacteria have a further claim. They were among the first organisms to produce oxygen by photosynthesis, and about 2.5 billion years ago that oxygen accumulated in the atmosphere and made the Earth suitable for other life. Their fossils are found in structures called stromatolites, discovered in Rajasthan and Madhya Pradesh.
Protista holds all single-celled eukaryotes that either have no cell wall or have one made of cellulose. They are microscopic and highly diverse, and include Amoeba, Euglena, Paramecium and Chlamydomonas. What separates them from Monera is the true, membrane-bound nucleus; what separates them from the plants, fungi and animals is that they are single cells.
They may be observed by making a hay infusion. A small sample of mown grass, straw or fodder is collected, and a small glass bottle filled one fourth with it. The bottle is then filled with stagnant or pond water and mixed, covered with muslin cloth tied on with thread, and left undisturbed for a week. The cloth is then opened just enough for a dropper, a drop is taken onto a clean slide, and the slide observed under a microscope. Because the infusion may smell bad, a lab coat, mask and gloves are worn, and it is discarded after autoclaving.
Protists live in water or moist places. Some are autotrophic and others heterotrophic. They are an important link in aquatic food chains, some producing oxygen and others serving as food for small animals, while some act as decomposers and help in nutrient cycling.
Flashcards (22)
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- Who Proposed What
- True or False: Kingdoms and Cells
- Fill the Gaps: Building the System
- Unscramble: Kingdoms and Cells
Kingdom Fungi and Kingdom Plantae
Fungi neither move nor feed themselves; they soak up what has died and give the soil its minerals back. Plants went the other way, and the five classes from algae to flowering plants read as one long argument about how to live out of the water.
What you will be able to do
- Describe Kingdom Fungi: their cells, how they feed, how they reproduce and what they do.
- Explain why yeast is a fungus though it is one cell.
- Describe Kingdom Plantae and name its five classes.
- Compare the five classes on body, transport tissue, seeds and dependence on water.
- Explain what a lichen is and why lichens serve as bioindicators.
Key points
Fungi are mostly multicellular eukaryotes whose cell walls are made of chitin.
They do not make their own food.
What has died or is rotting gives up its nourishment to them, drawn in along slender threads whose whole web is termed the mycelium.
The greater number live on what is already dead — shed leaves, fallen twigs, carcasses — and this makes them among the most important breakers-down in any ecosystem.
What they do is take complicated organic material apart into simple pieces, so that it returns to the soil as minerals anything can use.
Some enter into partnerships with other organisms, each side gaining — symbiosis — while others live at another's expense and make plants and animals ill.
Offspring come of them by either route, with or without a partner, and commonly through spores; warmth together with damp suits them best of all.
Yeast and Aspergillus mould are common fungi.
Yeast runs to one cell only, yet chitin in its wall is enough to put it among the fungi.
Mushrooms are macroscopic fungi that reproduce by spores.
Some fungi such as Aspergillus and Penicillium are used to make enzymes and antibiotics.
Without fungi, dead plants and animals would decay far more slowly, which would adversely affect soil fertility and ecological balance.
Those gathered wild are prized both at table and as remedies, and count among the forest goods that many communities, tribal communities in India among them, both use and look after.
Those communities possess traditional knowledge about which mushrooms are edible and which poisonous, based on folk taxonomy, some being used as food and some as medicine for treating various ailments.
Mushroom cultivation is becoming a promising vocation for livelihood, being easy and accessible because it needs minimal space, low investment and has a fast life cycle of 30 to 45 days.
Plants are multicellular, autotrophic organisms that perform photosynthesis.
Their cells have a rigid cell wall made primarily of cellulose, which provides support and protection.
Plants form the base of most food chains and release the oxygen that is essential for life on the Earth.
The kingdom falls into five classes, which run from the simplest upward: Thallophyta, Bryophyta, Pteridophyta, Gymnosperm, Angiosperm.
In the name Thallophyta, thallos means undifferentiated body and phyton means plant.
Of all plants these are about the plainest in build, and they keep to water or to ground that stays wet.
The body they form is called a thallus, plain enough that air, food and water pass straight in and out across its surface.
They are well adapted to aquatic habitats, and Spirogyra is an example of a thallophyte.
White-green patches on tree trunks, damp walls or stones are lichens, which villagers recognise as an indicator of a pollution-free environment.
Lichens change their colour with air pollutants, and researchers can work out the concentration of pollutants in the air from that colour, so lichens are natural bioindicators for measuring air quality.
Villagers collect lichens as forest produce, some types being called patthar ke phool and used as a spice, while others serve as medicines and as dyes that have given maroon, violet or burgundy colour to woollen and silk fabrics since ancient times.
What a lichen actually is, is two organisms living together to the advantage of both: an alga that makes its own food, and a fungus that does not.
The fungal partner provides protection while the algal partner photosynthesises and provides food.
A few sorts are poisonous, so telling one from another correctly matters before any of them is put to use.
In the name Bryophyta, bryon means moss and phyton means plant, and the group includes mosses and liverworts.
Bryophytes represent an important shift from water to land, and are seen as large green mats on damp rocks, on the walls of old buildings, or on soil surfaces.
They have a more differentiated body than thallophytes, with root-like structures called rhizoids, and may possess simple stem-like and leaf-like structures.
Damp shade is where they hold on, spreading as green mats over the ground, most noticeably in the rains; Marchantia and the mosses belong here.
Bryophytes lack vascular tissues for transporting water and food.
They require water for reproduction, since the male reproductive cells must swim to reach the female cells, and for this reason they are called the amphibians of the plant kingdom.
In the name Pteridophyta, pteris is derived from pteron meaning feather, and phyton means plant.
Pteridophytes such as ferns possess true roots, stems and leaves.
Cut a fern stem across and put it under a microscope: xylem and phloem are there, the one carrying water about the plant and the other food.
Even so, nothing comes of their reproduction unless water is at hand, and they form no seed.
In the name Gymnosperm, gymnos means naked and spermos means seed.
Gymnosperms such as pines and cycads are well adapted to cold and dry regions.
Leaves shaped like needles or scales give away little water and stand up to rough weather.
A seed is formed, which shelters the young plant within it and carries a store of food for its start.
Gymnosperms do not require aquatic conditions for fertilisation, and their seeds are not enclosed in fruits but are often exposed on cones.
In the name Angiosperm, angeion means vessel and spermos means seeds.
Angiosperms, or flowering plants, represent plants with the most complex body organisation, and possess well-developed roots, stems and leaves.
They produce flowers and fruits, the flowers attracting pollinators and so increasing the efficiency of reproduction, while the fruits help spread seeds to new locations.
Their seeds disperse through insects, birds, other animals, wind or water.
Between them these two structures open a great range of country to the group, and that is why no other kind of plant matches it for variety.
Among the first works of any scientific standing on the plants of India was Hortus Malabaricus, put together during the 1600s by Hendrik van Rheede, who had the help of Itty Achudan — herbalist, botanist and physician — and of others who knew the country.
Several hundred kinds of plant are set out in it, each with the ailments it was used against, and the book stands as an instance of old learning and new working side by side.
Taken in order from the simplest to the flowering, the groups amount to one long series of alterations in build, every one of them answering some difficulty of living out of water.
Early plants relied on water for support and for reproduction, and gradually the groups evolved transport tissues, then seeds, then flowers.
The many shapes plants take are so many different settlements of the same four demands — growing, carrying, breeding and lasting — each suited to a different sort of place.
Full explanation
12.6.3 Kingdom Fungi — walled eukaryotes, many-celled, that cannot feed themselves
A fungus is a eukaryote, usually of many cells, walled with chitin. Nothing in the group feeds itself by photosynthesis.
How they feed
Nourishment is drawn out of whatever is dead or rotting by slender threads, and the web those threads make is the mycelium.
| Most fungi | Saprophytes — feeding on dead organic matter: fallen leaves, twigs, dead organisms |
| Some | Mutualistic (symbiotic) with other organisms |
| Others | Parasites, causing diseases in plants and animals |
They take complicated organic material apart into simple pieces, so that it returns to the soil as minerals anything can use.
How they live and reproduce
- They reproduce both sexually and asexually, often by forming spores.
- They grow best in warm and moist conditions.
Examples
| Fungus | Note |
|---|---|
| Yeast | Unicellular — but its cell wall is chitin, so it is a fungus |
| Aspergillus mould | Used, with Penicillium, to make enzymes and antibiotics |
| Mushrooms | Macroscopic fungi that reproduce by spores |
One cell, but a chitin wall.
Why they matter
Take them away and dead plants and animals would rot far more slowly, to the cost of the soil's fertility and of the balance of the whole system.
Bridging Science and Society — wild mushrooms
Mushrooms gathered wild are worth eating for what is in them, as food and as medicine both, and count as something the forest yields that many communities gather and look after — tribal communities in India among them. Their traditional knowledge of which are edible and which poisonous rests on folk taxonomy; some are food and some are medicine.
Mushroom cultivation is now a promising vocation: minimal space, low investment, and a fast life cycle of 30–45 days.
12.6.4 Kingdom Plantae — walled eukaryotes, many-celled, that feed themselves
A plant is made of many cells, feeds itself, and does so by photosynthesis. Round each cell is a stiff wall, largely cellulose, which both holds the plant up and keeps it safe.
Nearly every food chain starts with plants, and it is plants that give off the oxygen without which nothing here would live.
Five classes: Thallophyta · Bryophyta · Pteridophyta · Gymnosperm · Angiosperm
Thallophyta (algae) — primitive plants
thallos = undifferentiated body; phyton = plant.
- About as plain as a plant gets, and found chiefly in water or where it is damp.
- The body is a thallus, undivided, so that gas, food and water pass straight in and out across it.
- Well adapted to aquatic habitats. Example: Spirogyra.
Bridging Science and Society — lichens
Those white-green patches on tree trunks, damp walls and stones are lichens, recognised by villagers as an indicator of a pollution-free environment.
Lichens change their colour with air pollutants. From the colour, researchers can find the concentration of pollutants — so lichens are natural bioindicators for air quality.
They are also collected as forest produce. Some, called patthar ke phool, are used as a spice; others as medicines, and as dyes giving maroon, violet or burgundy to woollen and silk fabrics since ancient times.
Biologically a lichen is symbiotic — one partner an autotrophic alga, the other a heterotrophic fungus. The fungus provides protection; the alga photosynthesises and provides food.
Some lichens are poisonous, so proper classification and identification matter.
Bryophyta — first steps on land, still needing water
bryon = moss; phyton = plant. Mosses and liverworts.
- They represent an important shift from water to land.
- Seen as large green mats on damp rocks, on walls of old buildings, or on soil.
- A more differentiated body than thallophytes: rhizoids (root-like), and sometimes simple stem-like and leaf-like structures.
- They survive in moist and shady places, especially during the monsoons. Examples: Marchantia, moss.
- They lack vascular tissues.
- They require water for reproduction, the male cells having to swim to the female cells.
Therefore they are called the 'amphibians' of the plant kingdom.
Pteridophyta — land, with a transport system
pteris from pteron = feather; phyton = plant. Ferns.
- They possess true roots, stems and leaves.
- Cut a fern stem across and xylem and phloem are there, the one carrying water about the plant and the other food.
- They still depend on water for reproduction.
- They do not produce seeds.
Gymnosperms — reproduction without water
gymnos = naked; spermos = seed. Pines and cycads.
- Well adapted to cold and dry regions.
- Leaves reduced to needles or scales lose little water and stand hard weather.
- They set seed, and a seed both shelters the embryo and carries a supply of food for it.
- Fertilisation needs no water here.
- No fruit closes over the seed; it generally sits open on a cone.
Angiosperms — efficient reproduction and seed dispersal
angeion = vessel; spermos = seeds. Flowering plants, with the most complex body organisation and well-developed roots, stems and leaves.
- They produce flowers and fruits.
- Flowers attract pollinators, increasing the efficiency of reproduction.
- Fruits help spread seeds to new locations — by insects, birds, other animals, wind or water.
These traits let angiosperms live across a wide range of environments, which makes them the most diverse plant group on the Earth.
Bridging Science and Society — Hortus Malabaricus
Among the first works of any scientific standing on the plants of India, put together during the 1600s by Hendrik van Rheede, who had the help of Itty Achudan — herbalist, botanist and physician — and of others who knew the country. It goes through hundreds of species and what each was used for in medicine: inherited knowledge and formal science in the same volume.
Table 12.3 — the classes compared
| Class | Advantage | Challenge |
|---|---|---|
| Thallophyta | Simple body aids survival and dispersal in water | Cannot live on land |
| Bryophyta | Plant amphibians; body adapted to moist land | Always need moisture |
| Pteridophyta | Live on land; transport water and food to all parts | No reproduction without water; no seeds |
| Gymnosperm | Leaves adapted for dry conditions; no water needed for reproduction; seeds | Seeds not covered by fruits |
| Angiosperm | Flowers, fruits, covered seeds; well-developed reproductive system | Reproduction depends on pollinating agents; complex tissue systems |
Set the plant groups in order from algae to angiosperms and one structural advance follows another, each answering some difficulty about living out of water. The earliest needed water to hold them up and to breed; after them came tissues for carrying material, then seed, then flower.
Thallo, Bryo, Pterido, Gymno, Angio.
Concepts and terms
The network formed by the fine filaments through which a fungus absorbs nutrients from dead or decaying matter.
An organism feeding on dead organic matter. Most fungi are saprophytes, which is why they matter so much as decomposers.
A plain, undivided plant body across which gas, food and water pass straight in and out. The mark of a thallophyte.
Xylem and phloem, which carry water and food through the plant. Bryophytes lack it; pteridophytes onward have it.
A mutual association of an autotrophic alga and a heterotrophic fungus. The fungus protects; the alga photosynthesises and feeds them both.
Did you know
A lichen changes colour according to the pollutants in the air, so researchers can read air quality off it.
Mushroom farming has a life cycle of only 30 to 45 days, and needs little space and little investment.
Hortus Malabaricus, compiled in the 17th century, describes hundreds of Indian plant species and their medicinal uses.
Memory tricks
The five plant classes in order — Thallo, Bryo, Pterido, Gymno, Angio — Water, damp land, transport tissue, seeds, flowers and fruits.
Why yeast is a fungus — One cell, but a chitin wall — The wall settles it, not the cell count.
Bryophytes — The amphibians of the plant kingdom — On land, but still needing water to reproduce.
Naked seed, vessel seed — Gymno means naked, angeion means vessel — On a cone, or inside a fruit.
Practice MCQs with answers (40)
- A Cellulose in the mould, chitin in the leaf
- B Chitin in both of them, without exception
- C Cellulose in both of them, without exception
- D Chitin in the mould, cellulose in the leaf
Show answer
Why:
The material of the wall names the kingdom.
- A By photosynthesis in green parts of the body
- B By swallowing small particles whole, as animals do
- C By drawing minerals directly through true roots
- D By absorption through fine filaments forming a mycelium
Show answer
Why:
They do not make their own food.
- A the reproductive spore it releases
- B the network formed by its fine filaments
- C the cell wall that surrounds each of its cells
- D the fruiting body seen above the ground
Show answer
Why:
Absorption happens through it.
- A feed on dead organic matter such as leaves and twigs
- B feed on living hosts, causing them disease
- C live in mutual partnership with another organism
- D make their own food from sunlight and water
Show answer
Why:
Hence their role as decomposers.
- A Build it up into still more complex substances
- B Store it unchanged within their own filaments
- C Convert it directly into oxygen and water
- D Break it into simpler substances available in soil as minerals
Show answer
Why:
Which is what keeps soil fertile.
- A a parasite
- B a saprophyte
- C a mutualistic symbiont
- D an autotroph
Show answer
Why:
Some fungi instead form mutual partnerships.
- A only sexually, and never by spores
- B only asexually, and never sexually
- C both sexually and asexually, often by forming spores
- D by producing seeds enclosed in fruits
Show answer
Why:
They grow best in warm and moist conditions.
- A it is multicellular like most fungi
- B its cell wall is made of chitin
- C it reproduces only by forming spores
- D it has no cell wall of any kind
Show answer
Why:
It is a single cell, which would otherwise suggest Protista.
- A microscopic fungi that reproduce by budding
- B single-celled fungi with cellulose walls
- C plants that have lost their chlorophyll
- D macroscopic fungi that reproduce by spores
Show answer
Why:
Yeast is the single-celled one.
- A enzymes and antibiotics
- B dyes and spices
- C biogas and manure
- D paper and textiles
Show answer
Why:
Both are fungi.
- A Decay would speed up, making soils excessively fertile
- B Plants would grow faster with less competition for minerals
- C Nothing much, since bacteria do the same work equally well
- D Decay would be greatly reduced, harming soil fertility and ecological balance
Show answer
Why:
They are the recyclers of nutrients.
- A large fields, heavy investment and a full year
- B specialised laboratories and trained technicians
- C minimal space, low investment and 30 to 45 days
- D cold regions and very high altitudes
Show answer
Why:
A fast life cycle is part of the appeal.
- A chitin
- B cellulose
- C calcium carbonate
- D protein
Show answer
Why:
It provides support and protection.
- A Four: Thallophyta, Bryophyta, Pteridophyta, Angiosperm
- B Five: Thallophyta, Bryophyta, Pteridophyta, Gymnosperm, Angiosperm
- C Three: Bryophyta, Gymnosperm, Angiosperm
- D Five: Monera, Protista, Fungi, Plantae, Animalia
Show answer
Why:
The last list is the five kingdoms, not the plant classes.
- A feather
- B naked
- C undifferentiated body
- D vessel
Show answer
Why:
Pteron means feather; gymnos naked; angeion vessel.
- A Transport of water and food through xylem and phloem
- B Reproduction without any need of water at all
- C Direct exchange of gases, nutrients and water with the surroundings
- D The enclosure of seeds within a protective fruit
Show answer
Why:
A simple body, well suited to water.
- A Bryophyta
- B Pteridophyta
- C Thallophyta
- D Gymnosperm
Show answer
Why:
The simplest of the plant classes.
- A two fungi of different species growing side by side
- B an alga alone, which has become able to live on stone
- C an autotrophic alga and a heterotrophic fungus in partnership
- D a moss growing over the surface of a fungus
Show answer
Why:
The fungus protects; the alga feeds them both.
- A The alga provides protection; the fungus photosynthesises and provides food
- B The fungus provides protection; the alga photosynthesises and provides food
- C Both partners photosynthesise, and neither provides protection
- D Neither partner contributes anything to the other at all
Show answer
Why:
Which is why it counts as mutualism.
- A they die completely the moment any pollutant appears
- B they change colour with air pollutants, and colour gives concentration
- C they grow faster the more polluted the air becomes
- D they release a gas that can be measured in the laboratory
Show answer
Why:
Villagers read the patches as a sign of clean air.
- A a fuel
- B a building material
- C a fertiliser
- D a spice
Show answer
Why:
Others serve as medicines and as dyes.
- A rhizoids
- B rhizomes
- C radicles
- D rachis
Show answer
Why:
They are not true roots.
- A They lack vascular tissues and require water for reproduction
- B They have vascular tissues but require water for reproduction
- C They lack vascular tissues but reproduce without any water
- D They have both vascular tissues and seeds
Show answer
Why:
The male cells must swim to the female cells.
- A They live in water but come out onto land to reproduce
- B They can breathe both in water and in air, like amphibians
- C They change their body form completely as they grow
- D They live on land but still need water in order to reproduce
Show answer
Why:
The shift from water to land is only partial.
- A Thallophyta
- B Pteridophyta
- C Angiosperm
- D Bryophyta
Show answer
Why:
Green mats in moist and shady places.
- A Bryophyta, with rhizoids and no true roots
- B Thallophyta, with an undifferentiated thallus
- C Pteridophyta, with true roots, stems and leaves
- D Gymnosperm, with seeds exposed on cones
Show answer
Why:
Pteris comes from pteron, meaning feather.
- A Food and water respectively
- B Water and food respectively
- C Only water, in both cases
- D Only air, in both cases
Show answer
Why:
Throughout the plant.
- A They need water to reproduce and have no vascular tissue
- B They produce no seeds and have no true roots
- C They have no vascular tissue and no true leaves
- D They need water to reproduce and produce no seeds
Show answer
Why:
The vascular tissue is precisely their advance.
- A To catch as much sunlight as possible in dim forests
- B To reduce water loss and withstand harsh conditions
- C To attract pollinating insects to the cones
- D To allow the seeds to be carried away by the wind
Show answer
Why:
They are adapted to cold and dry regions.
- A They allow the plant to reproduce entirely without pollen
- B They protect the developing embryo and contain stored food
- C They enable the plant to live permanently in water
- D They attract pollinators to the flowers of the plant
Show answer
Why:
And no aquatic conditions are needed for fertilisation.
- A not enclosed in fruits, and often exposed on cones
- B enclosed in fruits that help disperse them widely
- C never formed at all; gymnosperms are seedless
- D carried inside flowers until they germinate
Show answer
Why:
Gymnos means naked.
- A vessel
- B naked
- C feather
- D moss
Show answer
Why:
Spermos means seed, as in gymnosperm.
- A Flowers spread the seeds; fruits attract the pollinators
- B Flowers attract pollinators; fruits help spread seeds to new places
- C Both attract pollinators, and neither spreads the seeds
- D Both spread seeds, and neither attracts pollinators
Show answer
Why:
Efficiency of reproduction, and reach of dispersal.
- A Flowers and fruits let them occupy a wide range of environments
- B They are the only plants that can photosynthesise at all
- C They alone possess vascular tissues for transport
- D They require no pollinating agents of any kind
Show answer
Why:
They also have the most complex body organisation.
- A Itty Achudan alone, with no outside help of any kind
- B Carolus Linnaeus, as part of his two kingdom system
- C Hendrik van Rheede, with Itty Achudan and other local experts
- D Robert H. Whittaker, while proposing five kingdoms
Show answer
Why:
It describes hundreds of species and their medicinal uses.
- A A steady decrease in complexity from algae to flowering plants
- B A series of unrelated forms with nothing in common between them
- C A sequence of structural changes meeting the challenges of life on land
- D The gradual loss of the ability to photosynthesise
Show answer
Why:
Transport tissues, then seeds, then flowers.
- A 1 and 3 only
- B 1 and 2 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Pteridophytes produce no seeds at all.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Yeast is unicellular.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
It is the other way round. The assertion is sound, the reason false.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
Yeast is single-celled and still a fungus, so the assertion is false. The reason names what the kingdom actually turns on.
Important short questions (8)
Fungi are mostly multicellular eukaryotes whose cell walls are made of chitin. They do not make their own food, but absorb nutrients from dead or decaying matter through fine filaments that together form a network known as mycelium. Both kinds of reproduction occur, sexual and asexual, spores being the usual means; warmth and damp suit them best.
Most fungi are saprophytes and so act as decomposers, and what they eat is dead matter: leaf litter, fallen twigs, bodies. They take complicated organic material apart into simple pieces, so that it returns to the soil as minerals anything can use. Take them away and dead plants and animals would rot far more slowly, to the cost of the soil's fertility and of the balance of the whole system.
Because its cell wall is made up of chitin, which is the material that marks out the fungi. The number of cells is not the test; being single-celled would otherwise have suggested Protista.
A plant is made of many cells, feeds itself, and does so by photosynthesis. Round each cell is a stiff wall, largely cellulose, which both holds the plant up and keeps it safe. They form the base of most food chains and release the oxygen essential for life. The five classes are Thallophyta, Bryophyta, Pteridophyta, Gymnosperm and Angiosperm.
Biologically it is a symbiotic association of two organisms, an autotrophic alga and a heterotrophic fungus, the fungus providing protection and the alga photosynthesising and providing food. Lichens change colour with air pollutants, so researchers can find the concentration of pollutants from the colour, making them natural bioindicators of air quality. They are also collected as forest produce and used as spice, medicine and dye.
Bryophytes have a more differentiated body than thallophytes, with root-like rhizoids and sometimes simple stem-like and leaf-like structures, but they lack vascular tissues. Pteridophytes possess true roots, stems and leaves, and vascular tissues, xylem and phloem, which transport water and food throughout the plant. Both, however, still require water for reproduction, and neither produces seeds.
Leaves shaped like needles or scales give away little water and stand up to rough weather. A seed is formed, which shelters the young plant within it and carries a store of food for its start, and fertilisation calls for no water at all. The one drawback is that nothing encloses those seeds: they sit uncovered, commonly upon the woody cones.
They have the most complex body organisation, with well-developed roots, stems and leaves, and they produce flowers and fruits. A flower brings pollinators in, so that less is wasted in breeding; a fruit gets the seed carried off elsewhere, by insect or bird or beast, by wind or by water. These traits let angiosperms live across a wide range of environments.
Long answer questions (4)
Fungi are mostly multicellular eukaryotes whose cell walls are made of chitin. That material is what marks the kingdom out, which is why single-celled yeast is a fungus rather than a protist.
They do not make their own food. Nourishment is drawn out of whatever is dead or rotting by slender threads, and the web those threads make is the mycelium. Most are saprophytes, feeding on fallen leaves, twigs and dead organisms. Some instead enter into partnerships with other organisms, each side gaining — symbiosis — while others live at another's expense and make plants and animals ill.
Both kinds of reproduction occur, sexual and asexual, spores being the usual means; warmth and damp suit them best. Mushrooms are macroscopic fungi reproducing by spores; Aspergillus and Penicillium are used to make enzymes and antibiotics.
Their ecological importance is considerable. As decomposers they break down complex organic matter into simpler substances and make them available in soil as minerals. Without them, decay would be greatly reduced, and soil fertility and ecological balance would suffer.
They have a human importance too. Wild edible mushrooms are valued as food and medicine by many communities, including tribal communities in India, and mushroom cultivation is a promising livelihood needing little space, little investment and only 30 to 45 days.
Plants are multicellular autotrophs with rigid cell walls of cellulose, and the kingdom divides into five classes.
Thallophytes, the algae, are among the simplest plant forms, mostly in water or moist places. They form a thallus, a simple undifferentiated body allowing direct exchange of gases, nutrients and water with the surroundings. Spirogyra is an example. They cannot live on land.
Bryophytes, the mosses and liverworts, represent the shift from water to land. They have rhizoids and sometimes simple stem-like and leaf-like structures, but lack vascular tissues and need water for reproduction, the male cells having to swim. Hence they are called the amphibians of the plant kingdom.
Pteridophytes, the ferns, possess true roots, stems and leaves, and vascular tissues, xylem and phloem, transporting water and food throughout the plant. They still need water for reproduction and produce no seeds.
Gymnosperms, such as pines and cycads, suit cold and dry regions. Needle-like or scale-like leaves cut water loss; seeds protect the embryo and hold stored food; and fertilisation needs no water. But the seeds sit exposed on cones.
Angiosperms produce flowers, which attract pollinators, and fruits, which carry the seeds away.
Read in order, the five show transport tissues, then seeds, then flowers.
Thallophytes have a simple body that makes survival and dispersal in water easy. Their challenge is plain: they cannot live on land at all.
Bryophytes began to colonise land, and their bodies are adapted to moist ground, which earns them the name of plant amphibians. But they show only slight differentiation of parts, with nothing that is truly root, stem or leaf; they lack vascular tissues for transporting water and food; and they require water for reproduction, since the male cells must swim to reach the female. They always need moisture.
Pteridophytes live on land properly, possessing true roots, stems and leaves and vascular tissues that carry water and food to every part. Yet reproduction does not take place without water, and they produce no seeds.
Gymnosperms live on land, their needle-like leaves adapted for dry conditions, and water is not essential for fertilisation. They form seeds, which secure the continuity of life. The drawback is that those seeds are not covered in fruits, and lie exposed on cones.
Angiosperms possess well-developed roots, stems and leaves, reproduce sexually through flowers, and enclose their seeds within fruits, which disperse by insects, birds, animals, wind or water. Their reproduction, however, depends on pollinating agents, and their processes run through a complex and well-developed tissue system.
The white-green patches seen on tree trunks, damp walls and stones are lichens. What a lichen actually is, is two organisms living together to the advantage of both: an alga that makes its own food, and a fungus that does not. The fungal partner provides protection, while the algal partner photosynthesises and provides food. Neither would manage on that surface alone.
Scientifically they matter because they respond to the air around them. Lichens change their colour with air pollutants, and from that colour researchers can find the concentration of pollutants present. They are therefore natural bioindicators for the measurement of air quality. Villagers had worked it out for themselves by watching: where those patches grow, they take the air to be clean.
They matter to people in more direct ways too. Villagers collect them as forest produce. Some types, commonly called patthar ke phool, are used as a spice. Others serve as medicines. Others again have been used since ancient times to make dyes, giving maroon, violet or burgundy colour to woollen and silk fabrics.
One caution attaches to all this. A few are poisonous, which is reason enough to get the identification right before anyone makes use of them.
Flashcards (22)
Play this topic
- Groups and Their Marks
- True or False: Fungi and Plants
- Fill the Gaps: Walls, Tissues and Seeds
- Unscramble: Plants and Fungi
Kingdom Animalia: Invertebrates, Protochordates and Vertebrates
A sponge has no tissues at all; a starfish has a skeleton inside it. Between those two lies the whole invertebrate story — a mouth that is also an anus, then two openings, then segments, then armour — and after it, the rod that becomes a backbone.
What you will be able to do
- State what defines Kingdom Animalia and the criterion that splits it in two.
- Describe the eight invertebrate phyla and the structural advance each represents.
- Compare the phyla on habitat, level of organisation and skeleton.
- Explain what protochordates show and why the notochord matters.
- Describe vertebrates and name the five groups into which they fall.
Key points
Animals are multicellular and heterotrophic organisms, and depend on other organisms for their food.
Most animals show locomotion, rapid response to stimuli and coordinated behaviour.
Powers of that sort are what let an animal go looking for its food, keep clear of whatever hunts it, and deal with its surroundings as they alter.
Among the chief tests applied to animals is whether a notochord — a springy rod running the length of the body — is there or is not.
On that basis animals are classified into two groups, the non-chordata or invertebrata and the chordata.
Among certain of the chordates that rod is what the backbone afterwards grows out of.
The chordata is further classified as protochordata and vertebrata.
Having no such rod does not make these animals uniform: their bodies run all the way from the barely organised to the thoroughly systematised.
Studying them lets us trace how the animal body gradually changed over time, bringing advancement in traits such as movement, diverse feeding habits and better control and coordination, while also introducing exceptions and new challenges.
Few animal bodies are laid out as plainly as a sponge's — the Porifera, the pore-bearers: many cells, certainly, but nothing arranged into tissues and no organs at all.
Numerous pores in the body of a sponge allow water to flow through it continuously, bringing food particles and oxygen directly to individual cells and carrying the waste away.
A sponge stays where it is, and the sea is where it stays.
A single kilogram of the animal has been measured straining as much as twenty-four thousand litres of sea water in the course of one day.
Cnidarians such as Hydra, jellyfish and corals show a major change in body organisation, since tissue-level organisation is present in them.
That allows specialised cells to perform specific functions, as in the tentacles used for capturing prey.
Where a sponge must take whatever the current carries in through its holes, these animals reach out and seize what they want.
However, cnidarians possess a single opening that serves both for food intake and for waste removal.
Flatworms, the Platyhelminthes, show organisational advancement through bilateral symmetry, in which the body can be divided into two halves along one plane.
Such a body has distinct head and tail regions and distinct front and back regions, which allows better coordination of movement and marks the beginning of directional activity.
Being flat throughout, they manage the exchange of air across the body surface and need no organ set aside for it; but food and waste still share the one door.
Many flatworms have adopted a parasitic lifestyle, and hooks and suckers are present in the parasitic forms, which help them attach firmly to the host tissues to obtain nutrients.
Some infectious diseases are caused by parasitic worms, which enter our bodies through contaminated water and food and live inside the body, especially in the alimentary canal.
These worms take nutrients from our body and live as parasites, a host being the organism that lives in or on which another organism lives.
For this reason it is suggested that hands be washed properly, personal hygiene and good sanitary habits maintained, and only properly cooked food and boiled or filtered drinking water consumed.
Roundworms, the Nematoda, have elongated cylindrical bodies, and this structure lets them move efficiently through soil, water or host tissues.
That body form increases the range of environments in which roundworms can survive, despite a relatively simple internal organisation.
Now there are two apertures, a mouth and an anus, and organs grouped into systems, in which male and female differ.
Annelids such as earthworms represent a notable development in body organisation, their bodies being cylindrical and divided into segments.
They possess the organ system level of organisation, with muscles that help in locomotion and a nerve cord that helps in control and coordination.
Building the body of repeated units buys both suppleness and finer command of how it moves, and a hollow space within the body is present besides.
In the name Arthropoda, arthro means limbs and poda means appendages, and the group includes insects, crabs and spiders.
Their bodies are segmented, each segment specialised for a different function.
What marks the group out above all is the rigid case it has grown on the outside of itself.
That case does three things at once: it guards, it holds in moisture, and it gives strong muscles something to pull against — which together open up dry, exposed country to the group.
Molluscs such as snails, squids and octopuses have soft bodies and organ system level organisation.
A great many of them have grown a shell, which answers for the softness within, and the body itself falls into a clear head, a muscular foot and a raised hump.
Snail, squid and octopus are one design pulled three ways, each way answering what its surroundings asked of it.
In the name Echinodermata, echinos means spiny and derma means skin, and the group includes starfish and sea urchins.
Echinoderms possess a hard internal skeleton made of calcium carbonate.
No rod runs along them, yet that inner framework still guards the body and steadies its movement, and the general build comes close to that of far more advanced animals — a first leaning towards support from within.
Porifera live in marine water, are organised at the cellular level and have no skeleton.
Cnidaria live in fresh and marine water, are organised at the tissue level and have no skeleton.
Platyhelminthes live in water or inside a host, are organised at the organ level and have no skeleton.
Nematoda live in soil, water or inside a host, are organised at the organ system level with a digestive system, and have no skeleton.
Annelida live in moist soil or water, are organised at the organ system level and have no skeleton.
Arthropoda live on land or in water, are organised at the organ system level and carry an exoskeleton.
Mollusca live in water or on moist land, are organised at the organ system level and carry an exoskeleton.
Echinodermata live in marine water, are organised at the organ system level and carry an endoskeleton.
Laid out from the hole-bearers to the spiny-skinned, the bodies grow steadily more elaborately arranged.
Each new piece of structure does something for eating, for moving or for safety, and generally brings some fresh difficulty with it; between them these account for how so many kinds get by in so many places.
Amphioxus and its relatives carry that springy rod at some point in their lives, if not throughout.
It stiffens the body from within while leaving it free to bend, and that combination was a turning point in how animal bodies are built.
Protochordates are chordates of an early sort, and give some idea of what the notochord-bearing animals may have come from.
These animals carry a column of bone down the back, a framework inside the body which holds it up and shields what is most easily damaged — the brain and the cord behind it.
With that in place a creature may grow bulkier, move to better purpose, and carry elaborate systems of organs.
Vertebrates show advanced sensory abilities and coordinated behaviour.
They fall into five: the fishes, the amphibians, the reptiles, the birds and the mammals, sorted by where each kind lives, what covers it, and how it breeds.
Forests rich in biodiversity create physical, biological and chemical barriers that protect against disasters.
When the great cyclone struck Orissa in 1999, the mixed stands of mangrove told: settlements with more of that forest about them came off less badly than those without.
In the Western Ghats, forest diversity acts as a biological barrier against Monkey Fever, or Kyasanur Forest Disease, because many animals are hosts in which the virus cannot replicate.
Forest soil and plant roots carry a great mixture of microorganisms which take pollutants up, alter them or pull them apart, so that water comes out cleaner and the system is spared; mangrove mud catches silt and heavy metals besides, keeping them out of the rivers and the sea.
Full explanation
12.6.5 Kingdom Animalia — Multicellular, Heterotrophic Eukaryotes
An animal is built of many cells and cannot feed itself: something else has to be eaten. Most show:
- locomotion
- rapid response to stimuli
- behaviour that hangs together
Powers of that sort let an animal go looking for its food, keep clear of whatever hunts it, and deal with its surroundings as they alter.
The dividing criterion
Much of the sorting turns on one question: is there a notochord — a bendable rod running the length of the body — or is there not?
| Group | Notochord |
|---|---|
| Non-chordata (Invertebrata) | Absent |
| Chordata | Present |
Among some chordates that rod is what the backbone afterwards grows from. Chordata is further classified as protochordata and vertebrata.
A flexible rod, or none.
Invertebrates — animals without a notochord
How the body is put together varies enormously across them, from something quite plain to whole systems of organs. Going through them in order shows what happened to the animal body across time — how it moved, how it fed, how it governed itself — and throws up awkward cases and fresh difficulties as it goes.
Porifera (pore-bearers) — multicellularity without tissues
Few animal bodies are laid out as plainly as a sponge's.
Many cells, certainly — but nothing arranged into tissues, and no organs at all.
- Water runs through without stopping, by way of pores beyond counting.
- That water brings food particles and oxygen directly to individual cells and carries waste away.
- They remain fixed in one place, in aquatic environments.
Threads of Curiosity: a kilogram of sponge will put as much as 24,000 litres of sea water through itself in a day.
Cnidaria — true tissues and active feeding
Hydra, jellyfish and corals.
Tissue-level organisation is present, which lets specialised cells take on specific jobs — such as tentacles, used for capturing prey.
Unlike poriferans, they can catch prey with tentacles instead of depending on water currents.
There is, however, only one aperture, and it serves for taking food in and for putting waste out.
Platyhelminthes (flatworms) — bilateral symmetry and direction
Bilateral symmetry: the body can be divided into two halves along one plane, with distinct head-tail and front-back regions.
- This allows better coordination of movement — the beginning of directional activity.
- Being flat, the body lets gases pass in and out readily with nothing specialised for breathing.
- Yet still one aperture and no more.
Many are parasitic. Hooks and suckers in the parasitic forms help them attach firmly to host tissues to obtain nutrients.
Bridging Science and Society: parasitic worms enter through contaminated water and food and live in the alimentary canal, taking nutrients from the body. Hence: wash hands properly, maintain personal hygiene and good sanitary habits, eat properly cooked food and drink boiled or filtered water.
Nematoda (roundworms) — two openings
- Elongated, cylindrical bodies, allowing efficient movement through soil, water or host tissues.
- Simple as the inside remains, this widens the sorts of places they can live in.
- Now there are two apertures, a mouth and an anus.
- Organs are grouped into systems, and male and female differ in them.
Two openings, not one.
Annelida (segmented worms) — segmentation and body cavities
Earthworms.
- Bodies cylindrical and divided into segments.
- Organs grouped into systems: muscle to move with, a nerve cord to govern and coordinate.
- Being built in segments makes the animal both suppler and finer in its control.
- There is a cavity within the body as well.
Arthropoda — jointed appendages and an external skeleton
arthro = limbs; poda = appendages. Insects, crabs, spiders.
- Segmented bodies, with different segments specialised for different functions.
- The defining feature: a hard external skeleton, a rigid external covering.
It shields the animal, keeps water in and gives strong muscle something to pull against, which is why arthropods manage in places that are dry and without cover.
Mollusca — soft bodies, organ systems
Snails, squids, octopuses.
- Organ system level organisation with soft bodies.
- In many, a shell provides protection.
- The body falls into parts: a recognisable head, a foot of muscle, and a hump.
What this group demonstrates is that one basic layout can be pulled about in quite different ways according to what the surroundings ask of it.
Echinodermata — internal support without a notochord
echinos = spiny; derma = skin. Starfish, sea urchins.
- A rigid framework inside, of calcium carbonate.
- Notochord there is none, yet that framework still affords shelter and movement under control.
- Their body organisation comes close to that of more complex animals — a gradual shift towards internal skeletal support.
The invertebrate phyla compared (Fig. 12.16)
| Phylum | Habitat | Level of organisation | Skeleton |
|---|---|---|---|
| Porifera | Water (marine) | Cellular | — |
| Cnidaria | Water (fresh and marine) | Tissue | — |
| Platyhelminthes | Water / inside host | Organ | — |
| Nematoda | Soil / water / inside host | Organ system (digestive system) | — |
| Annelida | Moist soil / water | Organ system | — |
| Arthropoda | Land / water | Organ system | Exoskeleton |
| Mollusca | Water / moist land | Organ system | Exoskeleton |
| Echinodermata | Marine water | Organ system | Endoskeleton |
Pore, sting, flat, round, ring, joint, shell, spine.
Take the animals in order, sponge to echinoderm, and the body gets steadily more intricate. Each new piece of structure does something for eating, for moving or for safety — and generally brings some fresh difficulty with it.
Protochordates — the appearance of the notochord
Amphioxus and its kind carry a notochord at some point in life, if not throughout.
- It provides internal support without restricting movement — a crucial change in body organisation.
- Being chordates of an early sort, they give some idea of what the notochord-bearing animals may have come from.
Vertebrates — animals with a backbone
What a vertebrate has is a backbone, the vertebral column: a framework inside the animal that carries the body's weight and keeps the organs it cannot do without — brain, spinal cord — out of harm.
With it become possible:
- greater size
- movement that wastes little
- the development of complex organ systems
The senses are sharp and the behaviour hangs together.
They fall into five — fish, amphibians, reptiles, birds, mammals — sorted by where they live, what covers them and how they breed.
Bridging Science and Society — forests as barriers
Forests with rich biodiversity create physical, biological and chemical barriers:
- Mangroves and the 1999 Orissa super cyclone: villages with more mangroves experienced less destruction.
- Western Ghats and Monkey Fever (Kyasanur Forest Disease): forest diversity acts as a biological barrier, many animals being hosts in which the virus cannot replicate.
- Forest soils and roots: diverse microorganisms absorb, transform or break down pollutants, improving water quality. Mangrove soils trap sediments and heavy metals, preventing pollution spreading into oceans and rivers.
Concepts and terms
A flexible rod-shaped structure. Its presence or absence is a major criterion for classifying animals, and in some chordates it precedes the vertebral column.
Cellular in sponges, tissue in cnidarians, organ in flatworms, organ system from roundworms onward. The ladder of animal complexity.
The body divisible into two halves along one plane, with distinct head and tail and front and back. It allows better coordinated, directional movement.
Arthropods and molluscs carry a hard covering outside; echinoderms carry one of calcium carbonate inside, though they have no notochord.
Animals such as Amphioxus with a notochord at least once in life. Internal support that does not restrict movement — a primitive chordate.
Did you know
A single kilogram of sponge has been measured straining as much as twenty-four thousand litres of sea water in the course of one day.
In the 1999 Orissa super cyclone, villages with more mangroves around them suffered less destruction.
Forest diversity in the Western Ghats works against Kyasanur Forest Disease because many animals there are hosts in which the virus cannot replicate.
Memory tricks
The eight invertebrate phyla in order — Pore, sting, flat, round, ring, joint, shell, spine — Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata.
What splits Animalia in two — A flexible rod, or none — The notochord. Non-chordates lack it; chordates have it.
The great advance of the roundworm — Two openings, not one — A mouth and an anus, where cnidarians and flatworms have only one hole.
Arthropod names — Arthro means limbs, poda means appendages — And echinos means spiny, derma means skin.
Practice MCQs with answers (40)
- A multicellular autotrophs making their own food
- B multicellular heterotrophs depending on others for food
- C unicellular heterotrophs without a true nucleus
- D multicellular organisms with cell walls of chitin
Show answer
Why:
Most also show locomotion and rapid response to stimuli.
- A Make their own food from sunlight and water
- B Search actively for food and avoid predators
- C Survive without any other organisms at all
- D Reproduce without the need of a partner
Show answer
Why:
And interact dynamically with their surroundings.
- A a flexible rod-shaped structure running along the body
- B a hard covering grown on the outside of the body
- C a skeleton of calcium carbonate laid down within the body
- D a single opening serving both food intake and waste removal
Show answer
Why:
Its presence or absence splits the animal kingdom.
- A the protochordata and the vertebrata, these being the only two groups
- B the invertebrata and the vertebrata, with no third grouping at all
- C the Porifera and the Echinodermata, as the two extreme phyla
- D the non-chordata, which lack it, and the chordata, which have it
Show answer
Why:
Chordata then splits into protochordata and vertebrata.
- A The external skeleton, which hardens over the body surface
- B The vertebral column, which develops from it in those animals
- C The digestive system, which runs the length of the body
- D The nerve cord alone, with no skeletal structure involved
Show answer
Why:
Which is how the backbone arises.
- A unicellular, with all functions in one cell
- B multicellular, with organs but no organ systems
- C multicellular but lacking organisation of tissues and organs
- D multicellular, with a full organ system level
Show answer
Why:
Their level of organisation is cellular.
- A Tentacles capture food particles and bring them inward
- B Water flowing continuously through numerous pores brings them
- C A mouth takes in food which a gut then distributes
- D The sponge moves about in search of food particles
Show answer
Why:
The same current carries the waste away.
- A 2,400 litres of sea water per day
- B 240 litres of sea water per day
- C 24,000 litres of sea water per day
- D 24 litres of sea water per day
Show answer
Why:
Which is how a fixed animal manages to feed.
- A organ system organisation, with a complete digestive tract
- B the development of a hard external skeleton
- C tissue-level organisation, letting specialised cells do specific jobs
- D an internal skeleton made of calcium carbonate
Show answer
Why:
Tentacles are the obvious example.
- A It filters water through pores across its whole body
- B It absorbs nutrients directly from the surrounding water
- C It grazes on the sea floor using a muscular foot
- D It captures prey with tentacles rather than waiting on currents
Show answer
Why:
Active feeding, in short.
- A It has no cells specialised for any function whatever
- B It cannot capture prey, and depends on currents to bring it
- C It has no tissues, only individual cells working alone
- D A single opening serves for both food intake and waste removal
Show answer
Why:
Two openings begin with the roundworms.
- A can be divided into equal parts along any plane at all
- B cannot be divided into equal halves in any direction
- C can be divided into two halves along one plane
- D is divided into many repeating segments
Show answer
Why:
With distinct head-tail and front-back regions.
- A The capture of prey by means of stinging tentacles
- B Efficient filtering of water through numerous pores
- C The development of a hard external skeleton
- D Better coordination of movement, the beginning of directional activity
Show answer
Why:
A front end that goes first.
- A Through specialised respiratory organs in each segment
- B By water flowing through pores across the body
- C Through a pair of lungs opening at the mouth
- D By efficient diffusion across their flattened bodies
Show answer
Why:
No specialised respiratory organs are needed.
- A attach firmly to host tissues for obtaining nutrients
- B capture prey swimming past in open water
- C anchor the worm to rocks against the current
- D dig through soil in search of organic matter
Show answer
Why:
Many flatworms have taken to a parasitic life.
- A the skin of the hands during work
- B the air that is breathed in
- C the bite of an infected insect
- D contaminated water and food
Show answer
Why:
They then live especially in the alimentary canal.
- A Clean hands, good sanitation, cooked food, boiled or filtered water
- B Avoiding all contact with soil or with any animal
- C Eating only raw food, which carries no worms at all
- D Drinking only untreated water straight from a well
Show answer
Why:
The route in is contaminated food and water.
- A efficient movement through soil, water or host tissues
- B the capture of prey with stinging tentacles
- C filtration of water through numerous body pores
- D the growth of a hard external covering
Show answer
Why:
Which widens the range of environments it can occupy.
- A a single opening for food and waste alike
- B an internal skeleton of calcium carbonate
- C two openings, a mouth and an anus
- D a body divided into repeating segments
Show answer
Why:
Cnidarians and flatworms have only one.
- A The capture of prey by means of tentacles
- B Protection against water loss in dry places
- C Filtration of large volumes of sea water
- D Greater flexibility and more precise control of movements
Show answer
Why:
Muscles move it; a nerve cord coordinates it.
- A Muscles for locomotion and a nerve cord for coordination
- B A nerve cord for locomotion and muscles for coordination
- C Tentacles for both movement and coordination
- D An exoskeleton, which does both at once
Show answer
Why:
A body cavity is present as well.
- A limbs and appendages, describing the jointed legs of the group
- B spiny and skin, which is what echinos and derma mean
- C naked and seed, which is what gymnos and spermos mean
- D moss and plant, which is what bryon and phyton mean
Show answer
Why:
Echinos and derma give spiny skin.
- A a hard internal skeleton of calcium carbonate
- B a hard external skeleton, a rigid external covering
- C a flexible rod-shaped notochord along the back
- D a single opening for food intake and waste
Show answer
Why:
Their bodies are segmented, with specialised segments.
- A Protection, buoyancy in water and rapid growth
- B Reduced water loss, camouflage and the ability to fly
- C Protection, reduced water loss and support for powerful muscles
- D Support for muscles, gas exchange and food capture
Show answer
Why:
Which is what lets them live in dry exposed places.
- A a notochord, a nerve cord and a body cavity
- B numerous pores and no tissues at all
- C a distinct head, a muscular foot and a hump
- D tentacles and a single body opening
Show answer
Why:
In many, a shell protects the soft body.
- A How an internal skeleton develops from a notochord
- B How multicellularity arises without any tissues
- C How segmentation improves the control of movement
- D How one basic body plan can be altered along different lines
Show answer
Why:
Snails, squids and octopuses from one plan.
- A chitin, the same material as an arthropod's outer covering
- B cellulose, the same material as the wall of a plant cell
- C cartilage alone, with no mineral content of any kind
- D calcium carbonate, laid down within the body of the animal
Show answer
Why:
It gives protection and controlled movement.
- A It is external, though the animals possess a notochord
- B It is made of the same material as an arthropod's
- C It is internal, though the animals lack a notochord altogether
- D It is the first true vertebral column to appear
Show answer
Why:
A gradual shift towards internal support.
- A Cnidaria, whose specialised cells are gathered into tissues
- B Porifera, being multicellular but having no tissues at all
- C Platyhelminthes, which are organised at the organ level
- D Nematoda, which reach the organ system level of organisation
Show answer
Why:
Cnidaria are at the tissue level.
- A Nematoda, the cylindrical roundworms with a mouth and an anus
- B Annelida, the segmented worms possessing a distinct body cavity
- C Mollusca, the soft-bodied animals that often bear a shell
- D Platyhelminthes, the flat parasitic worms showing bilateral symmetry
Show answer
Why:
The organ system level begins with Nematoda.
- A Echinodermata with an exoskeleton covering the body outside
- B Echinodermata with an endoskeleton laid down inside the body
- C Arthropoda with an endoskeleton laid down inside the body
- D Annelida with an exoskeleton covering the body outside
Show answer
Why:
Arthropoda and Mollusca carry exoskeletons.
- A at least once during their life, though not always throughout
- B throughout life, in every one of them without exception
- C never at any stage, which is why they are called primitive
- D only after a vertebral column has already developed
Show answer
Why:
They are a primitive type of chordate.
- A External protection against predators
- B Internal support without restricting movement
- C A surface for gas exchange with the water
- D A store of food for the developing embryo
Show answer
Why:
A crucial change in body organisation.
- A The heart and the lungs, and no other organs besides these
- B The brain and the spinal cord, the most easily damaged organs
- C The stomach and the intestines, which lie within the trunk
- D The kidneys and the liver, which lie towards the back
Show answer
Why:
It supports the body besides.
- A Life only in water, and nowhere else at all
- B Reproduction without any need of a partner
- C Larger body size, efficient movement and complex organ systems
- D Feeding without any need of other organisms
Show answer
Why:
With advanced sensory abilities besides.
- A the presence or absence of a notochord
- B the level of organisation of their bodies
- C habitat use, body covering and reproduction
- D whether their skeleton is internal or external
Show answer
Why:
Fish, amphibians, reptiles, birds and mammals.
- A 1 and 3 only
- B 1 and 2 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Cnidarians have a single opening.
- A 2 and 3 only
- B 1 and 2 only
- C 1 and 3 only
- D 1, 2 and 3
Show answer
Why:
Annelids have no skeleton at all.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
Both are true, but being invertebrates is what they share; it cannot explain why one survives dry ground and the other does not.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
The notochord is what defines the chordates.
Important short questions (8)
Animals are multicellular and heterotrophic organisms depending on others for food, and most show locomotion, rapid response to stimuli and coordinated behaviour. The first division rests on the presence or absence of a notochord, a flexible rod-shaped structure: animals without it are the non-chordata or invertebrata, and those with it the chordata, which divides further into protochordata and vertebrata.
A sponge is multicellular but lacks any organisation of tissues and organs, so its level is cellular. Water flows through numerous pores, bringing food and oxygen directly to individual cells. A cnidarian has tissue-level organisation, which lets specialised cells take on specific jobs, such as tentacles for capturing prey. But it still has a single opening serving both for food intake and for waste removal.
One plane, and only one, cuts these animals into matching halves. That single plane gives them a front and a back and a distinct head and tail, so the body finally has a direction to it, and movement can be coordinated far better than before. Their flattened bodies permit efficient gas diffusion without respiratory organs. But there is still only one opening for food intake and waste elimination.
Its elongated cylindrical shape allows efficient movement through soil, water or host tissues, and so increases the range of environments in which it can survive, despite a relatively simple internal organisation. Its great advance is two openings, a mouth and an anus, and the organ system level of organisation is distinct in males and females.
The beetle adds a hard external skeleton, a rigid external covering, which the earthworm lacks. That covering gives protection, cuts water loss and anchors powerful muscles, allowing the beetle to survive in dry and exposed environments, while the earthworm keeps to moist soil or water. The beetle's segments are also specialised for different functions.
Molluscs such as snails, squids and octopuses show organ system organisation with soft bodies, often protected by a shell, the body having a distinct head, a muscular foot and a hump. Echinoderms such as starfish and sea urchins possess a hard internal skeleton of calcium carbonate. Although they lack a notochord, it gives them protection and controlled movement, showing a gradual shift towards internal skeletal support.
Animals such as Amphioxus that possess a notochord at least once during their life. The structure provides internal support without restricting movement, which is a crucial change in body organisation. They are chordates of an early sort, and give some idea of what the notochord-bearing animals may have come from.
It is a framework inside the animal that carries the body's weight and keeps the organs it cannot do without, brain and spinal cord, out of harm. With it become possible greater size, movement that wastes little, and organ systems of real complication; the senses are sharp and the behaviour hangs together. They are classified into fish, amphibians, reptiles, birds and mammals, on the broad patterns of habitat use, body covering and reproduction.
Long answer questions (4)
Few animal bodies are laid out as plainly as a sponge's: many cells, certainly, but nothing arranged into tissues and no organs at all, with water running in through pores beyond counting to bring food and oxygen to each cell on its own. They remain fixed in one place.
Cnidarians such as Hydra, jellyfish and corals show tissue-level organisation, so specialised cells can perform specific functions, such as tentacles for capturing prey rather than waiting on currents. But a single opening still serves for both food and waste.
Flatworms add bilateral symmetry, the body dividing into two halves along one plane with distinct head-tail and front-back regions, which allows better coordination of movement. Their flattened bodies permit gas diffusion without respiratory organs, though the single opening remains.
Roundworms bring two openings, a mouth and an anus, and organ system organisation, their cylindrical bodies moving efficiently through soil, water or host tissues.
Annelids add segmentation and a body cavity, with muscles for locomotion and a nerve cord for coordination, giving greater flexibility and more precise control.
Arthropods add a hard external skeleton, which protects, reduces water loss and supports powerful muscles. Molluscs show the plan modified in several directions, often with a shell. Echinoderms reach a hard internal skeleton of calcium carbonate, though they have no notochord at all.
Porifera live in marine water, are organised at the cellular level, and have no skeleton. Cnidaria live in fresh and marine water, are organised at the tissue level, and have no skeleton.
Platyhelminthes live in water or inside a host, are organised at the organ level, and have no skeleton. Nematoda live in soil, water or inside a host, are organised at the organ system level with a digestive system, and have no skeleton.
Annelida live in moist soil or water, are organised at the organ system level, and have no skeleton. So the first five phyla carry no skeleton at all.
Arthropoda live on land or in water, are organised at the organ system level, and carry an exoskeleton. Mollusca live in water or on moist land, are organised at the organ system level, and also carry an exoskeleton.
Echinodermata live in marine water, are organised at the organ system level, and carry an endoskeleton.
Read down the table, two patterns emerge. The level of organisation climbs from cellular through tissue and organ to organ system, and stays there from the roundworms onward. And a skeleton appears only at the end, first outside the body in two phyla, and then inside it in the last.
Much of the sorting turns on one question: is there a notochord, a bendable rod running the length of the body, or is there not? On that basis animals fall into two groups: the non-chordata or invertebrata, which lack it, and the chordata, which have it. Among some chordates that rod is what the backbone afterwards grows from. Chordata is further classified as protochordata and vertebrata.
Protochordates, such as Amphioxus, possess a notochord at least once during their life. The structure provides internal support without restricting movement, which is a crucial change in body organisation. They are chordates of an early sort, and they give some idea of what the notochord-bearing animals may have come from.
What a vertebrate has is a backbone, the vertebral column: a framework inside the animal that carries the body's weight and keeps the organs it cannot do without, brain and spinal cord, out of harm. With it become possible greater size, movement that wastes little, and organ systems of real complication; the senses are sharp and the behaviour hangs together.
They fall into five — fish, amphibians, reptiles, birds, mammals — sorted by where they live, what covers them and how they breed.
Forests with rich biodiversity create physical, biological and chemical barriers that protect against a range of challenges, and three examples are given.
The physical barrier is best shown by mangroves. When the super cyclone came ashore in Orissa in 1999, the mixture of trees in the mangrove belt told: a village with mangrove standing round it came off better than one without.
The biological barrier is shown in the Western Ghats. Forest diversity there acts against Monkey Fever, also called Kyasanur Forest Disease, because many of the animals present are hosts in which the virus cannot replicate. A diverse animal community therefore absorbs infections that would otherwise pass on, and rich biodiversity generally correlates with lower tick-borne disease risk.
The chemical barrier lies in the soil and roots. Forest soil and plant roots carry a great mixture of microorganisms which take pollutants up, alter them or pull them apart, so that water comes out cleaner and the system is spared. Mangrove mud in particular catches silt and heavy metals, keeping them out of the rivers and the sea.
The common thread is that variety itself does the work. A forest of one kind of tree, or one kind of animal, offers none of these three protections.
Flashcards (22)
Play this topic
- Phyla and Their Advances
- True or False: Bodies and Skeletons
- Fill the Gaps: The Animal Kingdom
- Unscramble: Animals and Their Parts
Adaptations, the Classification Hierarchy, Scientific Names and Biodiversity Under Threat
Classification works like an address: seven levels, each narrower than the last, ending in two Latin words that mean the same thing in every country. Fossils show the whole arrangement has a history — and the losses now running through it have a cause.
What you will be able to do
- Explain how structural features in vertebrates work as adaptations.
- State the seven levels of the classification hierarchy, in order.
- Write a scientific name correctly and explain what each part means.
- Describe how fossils serve as evidence of changing diversity.
- Explain what threatens biodiversity and what follows when a species is lost.
Key points
The diversity seen in animals today is the outcome of changes in body structure over long periods of time.
Fins and gills let a fish move and breathe in water.
Feathers and hollow bones make flight possible in birds.
The store of fat a camel carries, and the depth of a bear's coat in the far north, show how build itself can carry a creature through conditions that would otherwise finish it.
Milk-giving glands are a further change of build and of working alike, and what they buy is a better chance for the young.
None of these stands alone; taken together they are so many answers, made by different backboned kinds, to the same question of how to last where they live.
The sorting proceeds by stages, opening with groupings of the widest sort and closing on ones so narrow that only a single kind remains.
At each lower level, organisms share more common features.
Each lower group sits inside the group above it.
The order of the levels is kingdom, phylum, class, order, family, genus and species.
The thing works much as a postal address does. A house is reached by narrowing from country to town to street to number, and a living thing is placed in just that way, so that it can be named, set beside others and seen in its relations to them.
For the tiger, the levels run Animalia, Chordata, the sub-phylum Vertebrata, Mammalia, Carnivora, Felidae, Panthera and the species P. tigris.
For the pea, they run Plantae, Magnoliophyta, Magnoliopsida, Fabales, Fabaceae, Pisum and the species P. sativum.
A tiger is called bagh in Hindi, puli in Tamil, tiger in English and tigre in French, so if speakers from different regions discuss this animal, confusion follows.
The remedy adopted is one naming scheme good the world over, and it goes by the name of binomial nomenclature.
The system was introduced by Carolus Linnaeus in the 18th century.
Under it each kind carries a name of two words, cast in Latin or in a form made to look like Latin.
The tiger is Panthera tigris and the mango is Mangifera indica.
Of the two words the opening one — Panthera, Mangifera — names the near-relation group, and the one after it — tigris, indica — names the particular kind.
A genus groups closely related species that share common features, so that Panthera tigris, the tiger, and Panthera leo, the lion, both fall under the genus Panthera, the roaring cats, which possess the ability to roar and have a similar skull structure.
The second word marks off a set of creatures so much alike that they can breed together and leave young behind them.
Together the genus and species names form a unique scientific name used worldwide.
The first rule of writing a scientific name is that it has two parts, the genus and the species.
The second: the near-relation group goes first and takes a capital, the particular kind follows and takes none.
The third: set in slanting type where it is printed, and marked with a line beneath where it is written by hand.
Sorting life into five great groups took in more than anything before it had done, and yet the whole variety of living things still escaped it.
Genetics has since altered that scheme: better microscopes, and then genetic work, made it possible to set organisms side by side at the level of their DNA.
Inside every living cell sits the inherited material, DNA, holding the directions by which that cell grows and works; and where two organisms carry closely matching material, they are taken to come of the same stock.
Based on genetic data, Carl Woese in 1977 proposed the three domain system of Bacteria, Archaea and Eukarya.
That system showed microscopic life to be far more diverse than had previously been believed.
Classification systems keep changing because science evolves and progresses as we learn new things.
Aristotle's system worked for his time, but with new tools such as microscopes and technological advances such as staining techniques, scientists discovered microorganisms.
Those discoveries helped us understand the natural world better, and the biological classification changed accordingly, so that classification, and science with it, is an ongoing process of reasoning and change.
What is left of plants and creatures long dead, kept in the beds of rock, sand and mud that settled over them, is what we call a fossil.
Generally the older layers contain simpler organisms, while the newer layers show more complex forms.
India has yielded remains of real consequence: huge reptiles of the deep past, the earliest people, and plants of ages long gone.
They serve as a register kept by nature herself, from which the alteration of living things across ages beyond counting can be read off.
Birbal Sahni, who made his name on the remains of ancient plants, set up at Lucknow the institute of palaeosciences which now bears his name.
That institute continues his work on ancient plants and past environments to this day.
His work tied the plants now growing to the stock they came of, and made plain that living things on this planet form one long unbroken story.
Each species, large or small, has an important part in nature.
The green things build the food everything else eats and put out the air it breathes; the creatures carry pollen between blossoms and scatter seed away from the parent; and the least of them return what has died to the ground for use again.
What people do is wearing it down: fouling of air and water, clearing of forest, taking more than the land can spare, and the shifting of the climate itself.
A loss seldom stops where it began: whatever relied on the kind that went will thin out in its turn, and may in time be gone as well.
On finding a new organism, scientists compare it with the species already known, and sometimes the species name reflects the place of discovery, or honours a scientist.
The Purple Frog of Kerala, Nasikabatrachus sahyadrensis, carries in its second word the name of the Sahyadri range.
It passes the greater part of the year below the soil and shows itself only when the rains come, in order to breed; the family it belongs to is an old one, as the fossils show.
Finding it in 2003 threw light on amphibian groups of the distant past, and made plain how much the Western Ghats stand in need of protection.
On Loktak lake, inside the Keibul Lamjao National Park in Manipur, the grass grows on floating mats the people there call phumdis — a habitat with no real parallel anywhere.
These floating beds of soil carry a variety of rooted vegetation growing in rich organic matter, and their thickness varies from a few centimetres to two metres.
The plants growing there occur in no ordinary combination, and the place shelters a threatened form of the Sangai — the dancing deer — which belongs to Manipur and to nowhere else.
The deer spends considerable time on the phumdis, which are restricted to this small area.
The Sangai was declared extinct in 1951, and in 1953 it was rediscovered through the efforts of naturalists, who identified it by its unique characteristics of having hooves and elongated patterns.
The phumdis are now degenerating and the Sangai is listed in the IUCN Red Data list, so habitat loss will significantly affect the Sangai population, and efforts for conservation of both are in progress.
Full explanation
12.7 Adaptations as Outcomes of Structural Change
The range of animal forms now alive is what the body has come to after altering, slowly, for a very long while.
| Animal | Feature | What it makes possible |
|---|---|---|
| Fish | Fins and gills | Moving and breathing in water |
| Birds | Feathers and hollow bones | Flight |
| Camels | Fat storage | Survival in extreme conditions |
| Polar bears | Thick fur | Survival in extreme conditions |
| Mammals | Mammary glands | Improved survival of the young |
None of these traits stands by itself; each bears on the others, and together they show how one vertebrate or another meets what its surroundings demand.
12.7.1 The Hierarchical Nature of Classification
The scheme descends by stages, the widest groups first and then narrower and more particular ones.
- The lower you go, the more the members have in common.
- Each group sits wholly inside the one above.
The seven levels
Kingdom → Phylum → Class → Order → Family → Genus → Species
The whole thing reads like a postal address. An address narrows down to one house; this narrows down to one organism, and in doing so lets it be named, set beside others and studied, with its kinship plain.
Two worked examples (Fig. 12.17)
| Level | Tiger | Pea |
|---|---|---|
| Kingdom | Animalia | Plantae |
| Phylum | Chordata | Magnoliophyta |
| Sub-phylum | Vertebrata | — |
| Class | Mammalia | Magnoliopsida |
| Order | Carnivora | Fabales |
| Family | Felidae | Fabaceae |
| Genus | Panthera | Pisum |
| Species | P. tigris | P. sativum |
12.8 Scientific Naming — The Binomial System
One animal, four names: bagh to a Hindi speaker, puli to a Tamil one, tiger in English, tigre in French. Put those four speakers in a room together and nobody will be sure what is meant.
The remedy is a naming system everyone uses: binomial nomenclature, which Carolus Linnaeus brought in during the 1700s. Every organism gets a scientific name of two parts, in Latin or a Latinised form.
| Common name | Scientific name |
|---|---|
| Tiger | Panthera tigris |
| Mango | Mangifera indica |
- The first word — Panthera, Mangifera — is the genus.
- The second — tigris, indica — is the species.
What each part means
A genus groups closely related species that share common features.
Panthera tigris (tiger) and Panthera leo (lion) both sit under Panthera — the roaring cats, possessing the ability to roar, with a similar skull structure.
The species name indicates a group of organisms consisting of similar individuals capable of interbreeding and producing offspring.
Together, genus and species form a unique scientific name used worldwide.
Rules for writing scientific names
- Two words, one for the genus and one for the species.
- The genus comes first and takes a capital; the species comes second and does not.
- The name goes in italics in print, or underlined when handwritten.
Genus capital, species small, both in italics.
Ready to Go Beyond — the three domains
The five kingdom classification was more comprehensive than what came before, but still could not fully explain the diversity of life.
Better microscopes, and then genetics, made it possible to set organisms side by side at the level of their DNA. Inside every living cell is DNA, which holds the instructions by which the thing grows and works.
Where the DNA is close, the two are taken to be descended from the same stock.
Working from such data, Carl Woese put forward in 1977 a scheme of three domains:
- Bacteria
- Archaea
- Eukarya
What it brought out was that the small, invisible forms of life vary far more than anyone had supposed.
Threads of Curiosity — why systems keep changing
Science evolves and progresses as we learn new things.
Aristotle's system worked for his time. With new tools like microscopes and technological advances like staining techniques, scientists discovered microorganisms. Those discoveries helped us understand the natural world better, and biological classification changed accordingly.
Classification is never finished, and neither is science: both are an argument that keeps being revised.
12.9 Fossils as Evidence
A fossil is what is left of a plant or animal, kept in a bed of rock, of sand or of mud.
- As a rule the deeper and older the bed, the plainer the organisms in it.
- The shallower and newer, the more elaborate.
India has yielded some notable ones — dinosaurs of great size, early humans, plants of remote date.
They stand as a record nature kept itself, and from them one can follow what has happened to life across millions of years.
Meet a Scientist — Birbal Sahni
A scientist of standing whose subject was plants preserved as fossils. The institute he set up at Lucknow, now the Birbal Sahni Institute of Palaeosciences (BSIP), still pursues what he began on old floras and the conditions they grew in. His own work tied living plants back to their forerunners and made it clear that life here has a long history, all of a piece.
12.10 Biodiversity Under Threat
Size is no measure of importance here: every species is doing something in the system.
| Who | What they do |
|---|---|
| Plants | Produce food and oxygen |
| Animals | Pollinate flowers, and carry seeds about |
| Microorganisms | Recycle nutrients |
What is reducing it
Human activities:
- pollution
- deforestation
- the overuse of resources
- climate change
Lose one and whatever relied on it begins to thin out, and may go the same way.
Threads of Curiosity — the Purple Frog
When scientists discover a new organism they compare it with species already known. Now and then the second word points to where the thing was found, or carries somebody's name.
The Purple Frog of Kerala, Nasikabatrachus sahyadrensis, is named for the Sahyadris. It spends nearly the whole year below ground, surfacing in the rains and then only to breed, and the fossils place it in a very old family of frogs.
Finding it in 2003 told researchers a good deal about early amphibian groups, and pressed the case for guarding what is left in the Western Ghats.
Bridging Science and Society — phumdis and the Sangai
On Loktak lake, inside the Keibul Lamjao National Park in Manipur, the grass grows on floating mats the people there call phumdis — a habitat with no real parallel anywhere.
- Floating beds of soil with rooted vegetation and rich organic matter.
- Thickness varying from a few centimetres to two metres.
On them lives the Sangai, the dancing deer, an endangered animal found in Manipur and nowhere else, which passes much of its time out on the mats.
The deer was declared extinct in 1951. In 1953 it was rediscovered, through the efforts of naturalists, identified by its unique characteristics of hooves and elongated patterns.
The mats are breaking up, and the Sangai stands on the IUCN Red Data list. Lose the habitat and the deer will go with it; work is under way to save both.
Concepts and terms
Fins and gills, feathers and hollow bones, fat storage and thick fur, mammary glands — features that arose over long periods and support survival in particular environments.
Kingdom, phylum, class, order, family, genus, species. At each lower level organisms share more features, and every lower group lies inside the one above.
Two Latin or Latinised words: genus first with a capital, species second in lower case. Introduced by Linnaeus in the 18th century, and used worldwide.
Bacteria, Archaea and Eukarya, proposed by Carl Woese in 1977 from genetic data. It showed microscopic life to be far more diverse than had been believed.
Preserved remains of plants and animals in layers of rock, sand and mud. Older layers generally hold simpler organisms, newer ones more complex forms.
Did you know
The Sangai deer was declared extinct in 1951 and rediscovered in 1953, identified by its hooves and elongated patterns.
The Purple Frog spends most of the year underground and surfaces only during the monsoon to breed.
Phumdis, the floating beds of soil in Loktak lake, range from a few centimetres to two metres thick.
Memory tricks
The seven levels — Kingdom, phylum, class, order, family, genus, species — Broad to narrow, each inside the one above.
What the hierarchy is like — An address, from country down to house — It locates an organism exactly.
Writing a scientific name — Genus capital, species small, both in italics — Underlined when handwritten.
Reading rock layers — Older below and simpler, newer above and complex — Which is what makes fossils a record.
Practice MCQs with answers (40)
- A move on land and breathe in air
- B store fat against long journeys
- C move and breathe in water
- D keep warm in extremely cold conditions
Show answer
Why:
Feathers and hollow bones do the equivalent for birds.
- A Camels with fat storage, and polar bears with thick fur
- B Camels with thick fur, and polar bears with fat storage
- C Birds with fins and gills, and fish with feathers
- D Mammals with hollow bones for improved flight
Show answer
Why:
Both support survival under extreme conditions.
- A makes flight possible for the first time
- B improves the survival of the young
- C allows breathing under water for long periods
- D stores fat against a shortage of food
Show answer
Why:
An additional structural and functional change.
- A deliberate choices made by the animals themselves
- B a single event at one point in the Earth's history
- C differences in the food that each animal happens to eat
- D changes in body structure over long periods of time
Show answer
Why:
The features are interconnected across the vertebrates.
- A kingdom, class, phylum, family, order, genus, species
- B kingdom, phylum, class, order, family, genus, species
- C species, genus, family, order, class, phylum, kingdom
- D phylum, kingdom, class, family, order, species, genus
Show answer
Why:
Broad to narrow, in that order.
- A share fewer common features with one another
- B share more common features with one another
- C share exactly the same features as at every other level
- D cease to share any features with one another at all
Show answer
Why:
And every lower group lies within the one above.
- A Class, since it lies further down the hierarchy than genus
- B Both are the same, being at the same level of the hierarchy
- C Neither, since the hierarchy says nothing about membership
- D Genus, since it lies further down the hierarchy than class
Show answer
Why:
Lower means narrower and more alike.
- A assigns every organism a number that can be looked up
- B records where each organism was originally discovered
- C helps identify, compare and study organisms accurately
- D states which country each organism belongs to
Show answer
Why:
And shows how organisms are related.
- A Family Fabaceae, genus Pisum
- B Family Felidae, genus Panthera
- C Family Carnivora, genus Mammalia
- D Family Chordata, genus Vertebrata
Show answer
Why:
Carnivora is the order and Mammalia the class.
- A Phylum Magnoliopsida, class Magnoliophyta
- B Phylum Fabales, class Fabaceae
- C Phylum Chordata, class Mammalia
- D Phylum Magnoliophyta, class Magnoliopsida
Show answer
Why:
Fabales is the order and Fabaceae the family.
- A four different species of the genus Panthera
- B the four levels above genus in the hierarchy
- C four fossil species found in Indian rock layers
- D names for one animal in four different languages
Show answer
Why:
Which is why a universal system was needed.
- A Carl Woese, in the year 1977
- B Carolus Linnaeus, in the 18th century
- C Robert H. Whittaker, in the year 1969
- D Birbal Sahni, in the 20th century
Show answer
Why:
Woese proposed the three domains.
- A the local language, in two parts
- B Latin, but always in one single word
- C Latin or a Latinised form, in two parts
- D any language, provided it has three parts
Show answer
Why:
Genus first, species second.
- A indica
- B Mangifera
- C both of them together
- D neither of them
Show answer
Why:
The first word is always the genus.
- A all the organisms found within one single habitat
- B closely related species that share common features
- C organisms that look alike but are unrelated
- D every member of one kingdom of living things
Show answer
Why:
Panthera holds both the tiger and the lion.
- A The ability to roar, and a similar skull structure
- B The same species name, though different genera
- C Exactly the same habitat and the same prey
- D The inability to interbreed with anything at all
Show answer
Why:
Panthera is described as the roaring cats.
- A that live together within one particular habitat
- B that share a kingdom but nothing more specific
- C that have been given the same common name
- D of similar individuals capable of interbreeding and producing offspring
Show answer
Why:
Interbreeding is the test.
- A panthera Tigris
- B Panthera tigris
- C Panthera Tigris
- D PANTHERA TIGRIS
Show answer
Why:
Genus capitalised, species in lower case.
- A It is written in italics
- B It is written in capital letters
- C It is placed in quotation marks
- D It is underlined
Show answer
Why:
Italics are for printing.
- A It included too many kingdoms to be workable
- B It was based entirely on DNA, which was unreliable
- C It still could not fully explain the diversity of life
- D It had been proposed before microscopes existed
Show answer
Why:
Genetic research supplied what was missing.
- A live in the same habitat
- B belong to the same species always
- C have a common ancestry
- D have no relationship whatever
Show answer
Why:
DNA carries the instructions for growth and function.
- A Monera, Protista and Fungi
- B Bacteria, Archaea and Eukarya
- C Plantae, Animalia and Fungi
- D Bacteria, Protista and Plantae
Show answer
Why:
Proposed by Carl Woese in 1977.
- A That the smallest living things vary among themselves far more than anyone had supposed
- B That there are in fact only two kinds of living organism
- C That the five kingdom system was entirely mistaken
- D That DNA plays no part in determining relationships
Show answer
Why:
Genetic data revealed the diversity.
- A Scientists disagree with each other for no particular reason
- B Organisms themselves change from one group to another
- C Science evolves and progresses as new things are learnt
- D Older systems were deliberately made incorrect
Show answer
Why:
An ongoing process of reasoning and change.
- A Telescopes and photographic plates
- B Thermometers and barometers
- C Microscopes and staining techniques
- D Compasses and measuring tapes
Show answer
Why:
They led to the discovery of microorganisms.
- A the living descendants of ancient plants and animals
- B impressions made deliberately by early human beings
- C preserved remains of plants and animals in rock, sand and mud
- D minerals formed when volcanic rock cools slowly
Show answer
Why:
They act as natural records.
- A Simpler organisms below, more complex forms above
- B More complex forms below, simpler organisms above
- C Exactly the same organisms at every depth
- D No organisms of any kind at any depth
Show answer
Why:
Which is what makes the sequence readable.
- A proposing the three domain system of classification
- B introducing binomial nomenclature in the 18th century
- C discovering the Purple Frog in Kerala in 2003
- D studying fossil plants and founding an institute at Lucknow
Show answer
Why:
The Birbal Sahni Institute of Palaeosciences.
- A That present-day plants link to their ancestors, life having a connected history
- B That present-day plants are unrelated to any ancient forms
- C That fossils cannot tell us anything about past environments
- D That plants first appeared only a few thousand years ago
Show answer
Why:
His institute continues that work.
- A Plants
- B Microorganisms
- C Large mammals
- D Flowering plants alone
Show answer
Why:
Plants produce food and oxygen; animals pollinate and disperse.
- A Pollination, seed dispersal, decomposition and photosynthesis
- B Classification, naming, fossil study and conservation
- C Pollution, deforestation, overuse of resources and climate change
- D Rainfall, temperature change and the movement of continents
Show answer
Why:
All four are human activities.
- A Others that depend on it may decline and eventually disappear too
- B Nothing at all, since every species is entirely independent
- C All other species immediately increase in number
- D The habitat itself vanishes within a single season
Show answer
Why:
Dependence runs through an ecosystem.
- A the scientist who first described it
- B the monsoon season in which it breeds
- C the colour of the frog's skin
- D the Sahyadri Hills, where it was found
Show answer
Why:
A species name may name a place or honour a person.
- A In open water all the year round, never coming ashore
- B In trees all the year round, descending only to feed
- C On bare rock, breeding in the dry season only
- D Underground for most of the year, surfacing in the monsoon to breed
Show answer
Why:
It belongs to an ancient family of frogs.
- A the backwaters of Kerala, in the Western Ghats
- B the Sundarbans, at the mouth of the Ganga
- C Chilika lake, on the coast of Odisha
- D Loktak lake, in Keibul Lamjao National Park, Manipur
Show answer
Why:
Floating beds of soil with rooted vegetation.
- A A floating grassland found only in the Loktak lake
- B The dancing deer, endemic to Manipur and on the IUCN Red Data list
- C A frog discovered in the Western Ghats in 2003
- D A fossil plant studied by Birbal Sahni at Lucknow
Show answer
Why:
It was declared extinct in 1951 and rediscovered in 1953.
- A 1 and 3 only
- B 1 and 2 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
The genus takes a capital letter.
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3
Show answer
Why:
Linnaeus introduced binomial nomenclature.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
It is written in a Latinised form under one agreed system, which is what makes it universal. The assertion stands, the reason is false.
- A Both A and R are true, and R is the correct explanation of A
- B Both A and R are true, but R is not the correct explanation of A
- C A is true but R is false
- D A is false but R is true
Show answer
Why:
Microscopes, staining techniques, and then DNA.
Important short questions (8)
A fish is fitted with fins and gills, and so moves and breathes where it lives. A bird has plumage and light hollow bones, and so takes to the air. A camel stores fat and a polar bear grows a deep coat, each holding out against conditions that would finish most creatures. Milk-giving glands in the mammals are a further change of build and of working alike, buying a better chance for the young. None of these stands alone: together they are so many answers, made by different backboned kinds, to the same question of how to last where they live.
The sorting proceeds by stages, opening with groupings of the widest sort and closing on ones so narrow that only a single kind remains: kingdom, phylum, class, order, family, genus and species. The lower the stage, the more its members have in common, and each stage sits wholly inside the one above. The thing works much as a postal address does, letting a living thing be named, set beside others and seen in its relations to them.
A genus. It lies further down the hierarchy than a class, and at each lower level organisms share more common features while the group itself grows narrower. A class such as Mammalia takes in an enormous range of animals; a genus such as Panthera takes in a handful of closely related species.
Because one animal carries different names in different languages: a tiger is bagh in Hindi, puli in Tamil, tiger in English and tigre in French, so discussion across regions invites confusion. Carolus Linnaeus introduced the system in the 18th century, giving every organism a scientific name of two parts, in Latin or a Latinised form.
The first word is the genus, which groups closely related species sharing common features, as Panthera does for the tiger and the lion. The second is the species, a group of similar individuals capable of interbreeding and producing offspring. The genus begins with a capital letter and comes first; the species follows in lower case; and the whole is written in italics when printed or underlined when handwritten.
Bacteria, Archaea and Eukarya, proposed by Carl Woese in 1977. The five kingdom classification was more comprehensive than earlier systems but still could not fully explain the diversity of life. Advances in microscopes and genetic studies let scientists compare organisms at the DNA level, and since organisms with similar DNA are considered to share a common ancestry, the genetic data suggested this new arrangement. It showed that microscopic life forms are far more diverse than had been believed.
A fossil is what is left of a plant or animal, kept in a bed of rock, of sand or of mud. Generally the older layers contain simpler organisms while the newer layers show more complex forms, so the sequence can be read as a record. India has yielded some notable ones — dinosaurs of great size, early humans, plants of remote date — and they stand as a record nature kept itself, from which one can follow what has happened to life across millions of years.
What people do is wearing it down: fouling of air and water, clearing of forest, taking more than the land can spare, and the shifting of the climate itself. Every kind has its part — the green things build food and put out air, the creatures carry pollen and scatter seed, and the least of them return what has died to the ground. So a loss seldom stops where it began: whatever relied on the kind that went will thin out in its turn.
Long answer questions (4)
The scheme descends by stages, the widest groups first and then narrower and more particular ones. Two things hold at every step. At each lower level, organisms share more common features than at the level above. And each lower group sits inside the group above it, so the whole arrangement nests one inside another.
The seven levels run kingdom, phylum, class, order, family, genus and species.
The tiger runs Animalia, then Chordata and within it Vertebrata, then Mammalia, Carnivora, Felidae, Panthera, and last P. tigris. Each line narrows the field: Animalia takes in every animal, Mammalia only the mammals, Felidae only the cats, Panthera only the roaring ones.
The pea runs Plantae, then Magnoliophyta, Magnoliopsida, Fabales, Fabaceae, Pisum, and last P. sativum.
The whole thing reads like a postal address. An address narrows down to one house; this narrows down to one organism, and in doing so lets it be named, set beside others and studied, with its kinship plain. It also answers a practical question: a genus has fewer members than a class, but its members have far more in common.
One animal, four names: bagh to a Hindi speaker, puli to a Tamil one, tiger in English, tigre in French. Put those four speakers in a room together and nobody will be sure what is meant. The remedy is a naming system everyone uses, binomial nomenclature, which Carolus Linnaeus brought in during the 1700s. Each organism carries a name of two parts, put into Latin or made to look like it: Panthera tigris for the tiger, Mangifera indica for the mango.
The first word is the name of the genus. A genus groups closely related species that share common features. Panthera tigris, the tiger, and Panthera leo, the lion, both fall under Panthera, the roaring cats, which possess the ability to roar and have a similar skull structure.
The second word is the name of the species, which indicates a group of organisms consisting of similar individuals capable of interbreeding and producing offspring. Together the two form a unique scientific name used worldwide.
Three rules govern the writing. The name has two parts, genus and species. The genus begins with a capital letter and comes first, the species following in lower case. And the name goes in italics in print, or underlined when handwritten.
Classification changes because science evolves and progresses as we learn new things. Aristotle's system worked for his time, resting on what could be seen. With new tools such as microscopes, and technological advances such as staining techniques, scientists discovered microorganisms that no earlier scheme had room for. Those discoveries helped us understand the natural world better, and the classification changed accordingly. It is an ongoing process of reasoning and change, and revision is a sign of the method working rather than failing.
The five kingdom classification was itself part of that process. It offered a more comprehensive way to group organisms than the systems before it, but it still fell short of explaining the diversity of life.
Genetic research supplied what was missing. Better microscopes, and then genetics, made it possible to set organisms side by side at the level of their DNA. Inside every living cell is DNA, which holds the instructions by which the thing grows and works; where the DNA is close, the two are taken to be descended from the same stock.
On the basis of genetic data, Carl Woese in 1977 proposed the three domain system: Bacteria, Archaea and Eukarya. It showed that microscopic life forms are far more diverse than had previously been believed.
A fossil is what is left of a plant or animal, kept in a bed of rock, of sand or of mud. The layers themselves carry the information: generally the older ones contain simpler organisms while the newer ones show more complex forms, so the sequence read from the bottom upward is a sequence in time. India has yielded some notable ones — dinosaurs of great size, early humans, plants of remote date — and they stand as a record nature kept itself, from which one can follow what has happened to life across millions of years.
Birbal Sahni was a scientist of standing whose subject was plants preserved as fossils, and the institute he set up at Lucknow, now the Birbal Sahni Institute of Palaeosciences, still pursues what he began. His own work tied living plants back to their forerunners and made it clear that life here has a long history, all of a piece.
That history is now under pressure. Every species is doing something in the system: plants turn out food and oxygen, animals carry pollen and scatter seed, microorganisms put nutrients back into circulation. What we ourselves do — fouling the place, felling the forests, taking more than is there, altering the climate — is cutting that variety down.
And losses do not stay single. Lose one and whatever relied on it begins to thin out, and may go the same way.
Flashcards (22)
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- Names, Levels and Records
- True or False: Levels and Labels
- Fill the Gaps: Naming and Recording
- Unscramble: Ranks and Records
Class 9 Science Chapter 12 — frequently asked questions
Biodiversity is the immense variety of living organisms, from those invisible to the naked eye to giant trees, across every sort of habitat. It is essential because every organism plays a part in keeping nature stable and working: ocean algae release the greater part of the oxygen we breathe, fungi and bacteria decompose leaves and make the soil fertile, birds, bees and bats pollinate flowers. Plants capture sunlight to make the food nearly all other life depends on. These interconnections sustain ecosystems.
Endemic species are those restricted to particular regions of the world and found naturally nowhere else, such as the Nilgiri tahr, the lion-tailed macaque, Nepenthes khasiana and the Neelakurinji, all of which occur only in India. A biodiversity hotspot is a region that carries many species found nowhere else and has already lost much of its habitat. The Western Ghats, Indo-Burma including North East India, the Himalayas, and Sundaland including the Nicobar Islands are examples.
The country's own ground is varied. There is mountain in the north, desert in the west, rainforest in the North East and plateau in the south. Long shores run along both the Arabian Sea and the Bay of Bengal. Each region has its own soil types and its own conditions of temperature and rainfall, and these varied habitats together support a wide variety of species.
Around the 4th century BCE Aristotle grouped animals by their habitat, as of the land, the water or the air, and also by their external appearances. The limitation was that the system relied mainly on easily observable external characteristics, which do not reliably show how organisms are related.
Into Plantae went whatever stayed put and made its own food; into Animalia whatever went about and lived off other organisms. It failed because Amoeba, Paramecium and bacteria would not fit: Amoeba and Paramecium move about as animals do, yet are unicellular and heterotrophic, whereas plants and animals are multicellular.
First a third kingdom, Protista, was added to hold the unicellular microscopic organisms that fitted neither Plantae nor Animalia. Then improved microscopes showed that an amoeba has a true, membrane-bound nucleus while bacteria have none. Since both are unicellular but so unlike in that respect, bacteria were placed in a separate kingdom, Monera. That gave Plantae, Animalia, Protista and Monera.
Fungi are mostly multicellular eukaryotes whose cell walls are made of chitin. They do not make their own food, but absorb nutrients from dead or decaying matter through fine filaments that together form a network known as mycelium. Both kinds of reproduction occur, sexual and asexual, spores being the usual means; warmth and damp suit them best.
Most fungi are saprophytes and so act as decomposers, and what they eat is dead matter: leaf litter, fallen twigs, bodies. They take complicated organic material apart into simple pieces, so that it returns to the soil as minerals anything can use. Take them away and dead plants and animals would rot far more slowly, to the cost of the soil's fertility and of the balance of the whole system.
Because its cell wall is made up of chitin, which is the material that marks out the fungi. The number of cells is not the test; being single-celled would otherwise have suggested Protista.
Animals are multicellular and heterotrophic organisms depending on others for food, and most show locomotion, rapid response to stimuli and coordinated behaviour. The first division rests on the presence or absence of a notochord, a flexible rod-shaped structure: animals without it are the non-chordata or invertebrata, and those with it the chordata, which divides further into protochordata and vertebrata.
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