Our Environment · Class 10 Science: 64 flashcards

Everything that surrounds an organism — living and non-living components — and affects its life and development.

A self-contained unit of nature in which living organisms interact among themselves and with their non-living surroundings — e.g., a forest, pond or grassland.

Sunlight, air, water, soil (also temperature and minerals).

Producers, consumers and decomposers.

Green plants, algae and some bacteria (autotrophs) — they make their own food by photosynthesis, converting solar energy into chemical energy that feeds the entire ecosystem.

Herbivores (deer), carnivores (lion), omnivores (human/crow), parasites (lice, tapeworm, Cuscuta).

Microorganisms — bacteria and fungi — that break down dead organisms and organic waste into simple inorganic substances returned to the environment.

(1) They dispose of dead bodies and waste, cleaning the environment. (2) They release the nutrients locked in dead matter back into soil, water and air. (3) They thereby maintain the cycling of materials that keeps producers supplied.

Dead matter and waste would accumulate endlessly, nutrients would remain locked inside it, soils would become poor, producers would starve of minerals, and food chains would gradually collapse.

Natural: forest, pond, ocean (also lake, river, grassland, desert). Artificial: garden, crop field, aquarium (also parks).

Humans create and maintain it — choosing the species grown, supplying water and nutrients, and removing weeds and pests. It cannot sustain its structure without human management.

An aquarium is an incomplete artificial ecosystem — it lacks sufficient decomposers and natural nutrient cycles, so waste accumulates and must be removed by humans. A pond's complete community recycles its own waste.

A consumer that lives on or in a living host and derives its food from it — e.g., Cuscuta (amarbel), a parasitic plant; animal examples: lice, tapeworm.

Autotrophs (producers) make their own food from inorganic materials using sunlight. Heterotrophs (consumers and decomposers) cannot, and depend directly or indirectly on producers for food.

They secrete digestive enzymes onto the dead organic matter, breaking it down externally into simple soluble substances, which they then absorb.

Matter (nutrients like carbon, nitrogen, minerals) cycles repeatedly through producers, consumers, decomposers and the environment. Energy flows one-way — from the Sun through the chains, eventually lost as heat.

No — scavengers like vultures are consumers that eat dead animals in pieces. Decomposers (bacteria, fungi) chemically break down dead matter into simple inorganic substances.

(1) Sunlight (abiotic) drives photosynthesis in plants (biotic). (2) Soil minerals (abiotic) nourish plants, while decomposers (biotic) replenish those minerals — each side shapes the other.

Producers — because they alone bring new energy into the ecosystem by converting sunlight into food; all other organisms depend on that captured energy.

(a) Decomposer (fungus), (b) herbivore consumer, (c) omnivore consumer, (d) producer.

The sequence of organisms through which food and energy pass in an ecosystem, each feeding on the previous one — e.g., grass → deer → lion.

The direction of energy flow — from the organism that is eaten to the organism that eats it.

Each step or level of a food chain at which the transfer of food/energy takes place — producers form the first, herbivores the second, and so on.

First (T1): producers — green plants and algae. Second (T2): herbivores — the primary consumers.

About 1% of the solar energy falling on their leaves.

Only about 10% of the energy available at a trophic level is transferred to the next trophic level; the remaining ~90% is used in life processes or lost as heat.

T2 gets 1,000 J and T3 gets 100 J — each step keeps only one-tenth.

It is used by the organisms for their own life processes (respiration, movement, digestion, warmth) and lost as heat to the environment; some food is never digested or eaten.

Because only ~10% of energy passes each step, very little energy remains after 3–4 transfers — not enough to sustain another level of consumers.

Energy captured from the Sun moves only forward — producer to consumer — and at each step much is dissipated as heat, which cannot be recaptured or returned to any earlier level.

A network of interconnected food chains in an ecosystem, formed because most organisms eat and are eaten by more than one kind of organism.

It provides alternative food sources — if one species declines, its predators can switch to other prey instead of starving, so disturbances don't collapse the system.

Energy shrinks ~10× at each level, so each level can support only about a tenth of the biomass of the one below — numbers shrink up the pyramid.

The progressive increase in concentration of harmful non-biodegradable chemicals (such as pesticides like DDT) at each successive trophic level of a food chain.

They are neither broken down nor excreted — they accumulate in body fat. Each predator eats many prey over time, collecting the total stored chemical of all of them.

The highest (top consumers, often humans) — the chemicals concentrate at every step of the chain, so whoever eats last accumulates the most.

Sprayed on crops, they enter grains, fruits and vegetables directly, and reach milk and meat through fodder — then accumulate in human tissues since they are non-degradable.

Washing removes only surface residues; the chemicals absorbed INTO the plant's tissues remain — a key reason to minimise persistent pesticides.

Eating plants puts humans at T2 (receiving 10% of plant energy); eating grain-fed meat puts us at T3 (10% of 10% = 1%). Plant-based diets waste one less energy transfer.

Algae → water insects/zooplankton → small fish → big fish (or heron/kingfisher).

Pesticide concentration increases (biological magnification); energy per level decreases (10% law).

Grasshoppers would multiply unchecked (their predator gone) and would then overgraze and destroy the grass; snakes would starve or migrate — the chain's balance collapses in both directions.

Substances that are broken down into simpler harmless substances by microorganisms (bacteria and fungi) — e.g., fruit/vegetable peels, paper, cotton cloth, cow dung (also wood, leaves, food waste).

Substances that cannot be broken down by microorganisms — e.g., plastics, glass, metals, thermocol (also synthetic fibres and pesticides like DDT).

(1) Rotting heaps produce foul smells. (2) They become breeding grounds for flies, mosquitoes and disease-causing germs.

(1) It persists for centuries, polluting soil and choking drains. (2) Animals (cattle, marine life) die swallowing it. (3) Chemicals like pesticides biomagnify up food chains into our own food.

Ozone (O₃) is a molecule of three oxygen atoms; the ozone layer is a region rich in ozone in the upper atmosphere (stratosphere).

It absorbs most of the Sun's harmful ultraviolet (UV) radiation, protecting living organisms from its damaging effects.

High-energy UV radiation splits O₂ molecules into free oxygen atoms; each free atom then combines with another O₂ molecule to form ozone: O₂ →(UV) 2O; O + O₂ → O₃.

Chlorofluorocarbons (CFCs) — used as refrigerants in fridges and ACs, as propellants in spray cans, and in foam manufacturing.

CFCs drift to the stratosphere where UV breaks them apart, releasing chlorine atoms; each chlorine atom acts repeatedly, destroying thousands of ozone molecules.

Over Antarctica, reported in 1985 — a drastic seasonal thinning of the ozone layer each southern spring.

(1) Skin cancer, (2) cataracts and eye damage, (3) weakened immune systems, (4) damage to crops and to ocean plankton (the base of aquatic food chains).

The 1987 international agreement to phase out the production and use of CFCs and other ozone-depleting substances — signed by every country; the ozone layer is now recovering because of it.

Stratospheric ozone (high up) absorbs UV and protects life — good. Ground-level ozone, formed in traffic smog, irritates the lungs and damages plants — a pollutant.

Separating waste at the source into biodegradable (wet) and non-biodegradable/recyclable (dry) streams. It matters because mixed waste can neither be composted cleanly nor recycled — separation makes both streams usable.

Reduce (carry a cloth bag to avoid plastic ones), Reuse (use glass jars for storage), Recycle (send newspapers and bottles for reprocessing). The order reflects priority.

Converting biodegradable waste into manure by burying it in a pit and letting microorganisms decompose it over weeks.

Preparing compost with the help of red earthworms, which eat biodegradable waste and excrete nutrient-rich castings — faster and richer than plain composting.

By incineration — controlled burning at very high temperature, which destroys pathogens and toxic substances safely.

A lined, engineered pit where residual waste is compacted and covered with soil, protecting groundwater and preventing scattering — for waste that can be neither composted nor recycled.

Stray cattle and animals eat the food along with the bag; the plastic blocks their digestive tracts, often fatally. Mixed plastic also ruins compost.

DDT — it persists in soil and water and undergoes biological magnification, concentrating up food chains to harm top consumers including birds and humans.

About 450 years — while a vegetable peel decomposes in 1–4 weeks.