Our Environment · Class 10 Science: 162 MCQs with answers

Q1. Which of these is an ABIOTIC component?

Q2. Which of these is a BIOTIC component?

Q3. Bacteria and fungi that feed on dead matter are called:

Q4. Lice and tapeworms, which feed on a living host, are:

Q5. The nutrients locked in dead organisms are released back to the soil by:

Q6. What is an ecosystem? Give two examples each of natural and artificial ecosystems.

Q7. Distinguish between biotic and abiotic components with two examples of each.

Q8. Who are producers? Why are they called the foundation of every ecosystem?

Q9. Classify consumers into their four categories with one example each.

Q10. What are decomposers? Write their two most important roles.

Q11. Sort into producers, consumers and decomposers: grass, mushroom, frog, algae, bacteria, cow, tiger.

Q12. According to the 10% law, the energy transferred to the next trophic level is about:

Q13. If plants have 1,000 J of energy, herbivores eating them get about:

Q14. Food chains generally have at most:

Q15. The increase of pesticide concentration up a food chain is called:

Q16. Which chemical is the classic example of biological magnification?

Q17. The maximum concentration of harmful chemicals accumulates in:

Q18. What is a food chain? Write a food chain of a grassland with four trophic levels.

Q19. State the 10% law of energy transfer with a numerical illustration.

Q20. Differentiate between a food chain and a food web.

Q21. If 10,000 J of energy is available at the producer level, how much reaches a T4 top carnivore? Show the steps.

Q22. Substances broken down by microorganisms are called:

Q23. The ozone hole was first discovered over:

Q24. Increased UV radiation causes:

Q25. The three Rs of waste management are:

Q26. Converting biodegradable waste into manure using earthworms is called:

Q27. Hospital waste is best disposed of by:

Q28. Differentiate between biodegradable and non-biodegradable substances with two examples of each.

Q29. What is the ozone layer? How does it protect us?

Q30. What are CFCs? How do they damage the ozone layer?

Q31. List the harmful effects of the depletion of the ozone layer.

Q32. Suggest four ways of managing household garbage responsibly.

Q33. Two waste heaps lie behind a school: heap A of fruit peels and leaves, heap B of plastic wrappers. Describe the state of both heaps after three months and justify.

Q34. Which pair of organism and role is matched CORRECTLY?

Q35. An aquarium must be cleaned periodically because it:

Q36. In an ecosystem, materials like carbon and minerals:

Q37. The correct sequence of dependence is:

Q38. A garden differs from a forest mainly in that a garden:

Q39. Which of these acts as a PRODUCER in a pond ecosystem?

Q40. The number of species and complexity is generally GREATER in:

Q41. Fungi growing on a fallen log are acting as:

Q42. From the list — sunlight, soil, deer, bacteria, temperature, algae — the BIOTIC members are:

Q43. The term for organisms feeding on dead and decaying matter is:

Q44. What would be the consequences of the absence of decomposers in an ecosystem?

Q45. Why are crop fields known as artificial ecosystems?

Q46. An aquarium and a pond both contain water, fish and plants. Why does only the aquarium need regular cleaning?

Q47. Describe the components of an ecosystem in detail — abiotic factors and the three biotic categories — showing with a pond example how each part depends on the others.

Q48. In grass → grasshopper → frog → snake → eagle, the eagle is at trophic level:

Q49. The 90% of energy NOT passed on at a trophic level is:

Q50. Which level has the LEAST total energy in an ecosystem?

Q51. If the energy at T3 is 20 J, the energy that was at T1 was about:

Q52. A human eating rice occupies trophic level:

Q53. A human eating fish that ate insects that ate algae occupies:

Q54. Food webs make ecosystems stable because they provide:

Q55. The number of organisms generally ______ as we go up a food chain.

Q56. Energy CANNOT be recycled in an ecosystem because:

Q57. Which is NOT a consequence of the 10% law?

Q58. DDT enters a food chain mainly through:

Q59. Biological magnification occurs only for chemicals that are:

Q60. Which human food would carry the HIGHEST magnified pesticide dose, other things equal?

Q61. Which practice REDUCES biological magnification in human food?

Q62. Why do food chains rarely extend beyond four trophic levels?

Q63. Why is the flow of energy in an ecosystem said to be unidirectional?

Q64. What is biological magnification? Why does it occur only with certain chemicals?

Q65. The concentration of a pesticide was found to be highest in human beings among all organisms tested. Explain why.

Q66. Can the organisms of any ecosystem manage without decomposers even though decomposers are not part of the grazing food chain? Explain briefly.

Q67. Explain the flow of energy in an ecosystem from sunlight to a top carnivore, including the 1% capture figure, the 10% law at each transfer, where the rest goes, and the two major consequences of this pattern.

Q68. Which gas equation shows ozone formation?

Q69. Ground-level ozone is:

Q70. Damage to ocean plankton from UV is serious because plankton:

Q71. Which action follows 'REDUCE', the first R?

Q72. Reusing a jam jar to store spices is an example of:

Q73. Melting old newspapers into fresh paper is:

Q74. Mixed (unsegregated) waste is a problem because:

Q75. The link between non-biodegradable pesticides and food chains is:

Q76. Which waste pair is sorted CORRECTLY into a green bin for biodegradable waste and a blue bin for the rest?

Q77. The recovery of the ozone layer teaches that:

Q78. Which is the correct increasing order of decomposition time?

Q79. Why are some substances biodegradable and some non-biodegradable?

Q80. How is ozone formed in the upper atmosphere? Give the equations.

Q81. What steps were taken internationally to protect the ozone layer, and with what result?

Q82. Why is it better to use paper or cloth bags than plastic bags, even though paper production also consumes resources?

Q83. Explain the full story of ozone: what it is, how it forms, what it does for us, how CFCs deplete it, the consequences of depletion, and how the world responded.

Q84. Consider these statements about an ecosystem. I. It contains living organisms and the non-living surroundings they interact with. II. Air, water, soil and sunlight are its abiotic components. III. Plants, animals and microbes are its biotic components. IV. An ecosystem contains only its living members. Which statements are correct?

Q85. Which statement best explains why producers are called the ENTRY POINT of energy into an ecosystem?

Q86. A sealed glass jar holds pond water, algae, a few small fish and microbes, and is kept in the light. Which statement best explains why it can keep going for weeks?

Q87. A deer, a lion, a crow and a vulture feed respectively as:

Q88. Which statement best explains why being an OMNIVORE is an advantage?

Q89. Which statement best explains why a garden is called an ARTIFICIAL ecosystem while a forest is called a natural one?

Q90. Consider these statements comparing a forest with a crop field. I. The forest has far more species. II. The forest's food web is more complex. III. The crop field needs continuous human input to persist. IV. The crop field is more likely to survive a new pest. Which statements are correct?

Q91. Which sequence correctly shows the order of dependence in an ecosystem?

Q92. Which statement best explains why an aquarium has to be cleaned from time to time while a natural pond does not?

Q93. How do decomposers feed?

Q94. Which statement correctly distinguishes a CONSUMER from a DECOMPOSER?

Q95. Which of these is NOT a role played by decomposers?

Q96. Which abiotic factor does most to decide whether a given region becomes a desert or a forest?

Q97. Assertion (A): Decomposers are essential to the fertility of soil. Reason (R): They break dead bodies and waste into simple substances that plants can absorb again.

Q98. Assertion: An aquarium is an artificial ecosystem. Reason: Its inhabitants and conditions are selected and maintained by humans.

Q99. If every producer were removed from an ecosystem, the FIRST group to starve would be the:

Q100. If all the HERBIVORES in a grassland vanished, the producers would at first:

Q101. Which statement best explains the phrase 'matter cycles but energy flows'?

Q102. A field trial removes all the soil microbes from a plot of land. Over the following months, the plot's plants are most likely to:

Q103. Which sequence lists ONLY consumers?

Q104. In a sealed, sunlit glass jar containing pond water, algae, small fish and microbes, the system can persist for a long time because:

Q105. Cuscuta growing on a host tree, and a fungus growing on a fallen log, are respectively:

Q106. A farmer burns all the crop residue on the field after each harvest. A likely long-term consequence is that:

Q107. The main difference between a consumer and a decomposer is:

Q108. Consider these statements about the three groups in an ecosystem. I. Producers bring energy into the system from outside it. II. Consumers pass that energy along but add none of their own. III. Decomposers return matter to a form producers can use again. IV. An ecosystem could manage without decomposers if it had enough producers. Which statements are correct?

Q109. 'Matter cycles but energy flows one-way in an ecosystem.' Justify this statement.

Q110. 'Decomposers are as important to an ecosystem as producers.' Defend this statement with at least four arguments, and describe what a world without decomposers would look like within a few decades.

Q111. Compare natural and artificial ecosystems under five headings: origin, maintenance, diversity, completeness of cycles, and stability — with examples. Why can even a well-kept garden not equal a forest?

Q112. Design a self-sustaining sealed jar ecosystem ('ecosphere') for a science exhibition. State what you would include and why (component by component), what single input it still needs, and what would go wrong if each biotic category were left out.

Q113. Consider these statements about trophic levels. I. Producers occupy the first trophic level. II. Herbivores occupy the second. III. The carnivores that eat herbivores occupy the third. IV. The number of organisms usually increases as we go up the chain. Which statements are correct?

Q114. Which statement best explains why a food chain is drawn as a straight line while a food web is drawn as a network?

Q115. In the food chain grass → grasshopper → frog → snake, the arrows point from the eaten to the eater. What do the arrows actually represent?

Q116. Green plants capture only about 1% of the sunlight falling on their leaves, and only about 10% passes to each next level. Together these two figures explain why:

Q117. Which statement best explains why a food WEB makes an ecosystem more stable than a set of separate food chains would?

Q118. Assertion (A): Energy cannot be recycled in an ecosystem, though matter can. Reason (R): At every trophic level most of the energy is lost as heat to the surroundings, and heat cannot be recaptured by living things.

Q119. In the food chain grass → grasshopper → frog → snake → eagle, the SECOND consumer is the:

Q120. In a pond chain algae → zooplankton → small fish → kingfisher, removing the small fish would first cause:

Q121. The energy available to the snake in grass(5000 J) → grasshopper → frog → snake is about:

Q122. Assertion: Top carnivores are few in number. Reason: Very little energy remains at the highest trophic level.

Q123. Assertion: DDT concentration is higher in fish-eating birds than in the lake's water. Reason: DDT is biodegradable and dissolves at each level.

Q124. Two chains: (A) wheat → human. (B) wheat → goat → human. For the same wheat energy, the human receives:

Q125. Which statement about a food WEB is correct?

Q126. A sparrow eating seeds is at T2; the same sparrow eating insects (which ate leaves) is at:

Q127. If an ecosystem's producers total 10⁷ J, the MAXIMUM sustainable trophic levels (needing ≥10 J at the top) is about:

Q128. Sea chains often support 4–5 levels more easily than land chains because:

Q129. Case: A farmer sprays pesticide weekly. Years later, eagles near his fields lay thin-shelled eggs. The connecting mechanism is:

Q130. Case: In a grassland, foxes eat both rabbits (T2) and quail that eat insects (making quail T3). When eating quail, the fox operates at:

Q131. Which shape represents the energy available at successive trophic levels, and why?

Q132. Which of these can NEVER occupy the first trophic level of a food chain?

Q133. What will happen if we kill all the organisms of one trophic level — say all herbivores — in a grassland?

Q134. Define biological magnification and explain its mechanism step by step using the DDT example (water → plankton → small fish → large fish → fish-eating birds). Why do the levels lowest in energy end up highest in poison, and what practices can reduce the problem?

Q135. Construct a food web for a garden ecosystem containing: plants, caterpillars, grasshoppers, rats, sparrows, frogs, snakes and hawks. Then use it to answer: (a) which organism occupies more than one trophic level, (b) what happens if the sparrows disappear, (c) why the web is more stable than any single chain within it.

Q136. A town debates two lunch programmes for its school: Programme A serves grain-and-vegetable meals; Programme B serves meat from grain-fed animals. Using the 10% law, compare the land/grain requirements of the two programmes, and discuss one health-related advantage of Programme A connected to biological magnification.

Q137. Consider these statements about wastes. I. Biodegradable wastes are broken down by microorganisms. II. Fruit peel, paper, cotton and cow dung are biodegradable. III. Plastics, glass and metals are non-biodegradable. IV. Non-biodegradable wastes break down slowly but do break down in the end. Which statements are correct?

Q138. Which statement best explains why non-biodegradable waste is a more serious long-term problem than biodegradable waste?

Q139. Ozone is formed in the upper atmosphere when ultraviolet light splits oxygen molecules and the free atoms join other oxygen molecules. Which statement about ozone is correct?

Q140. Which statement best explains why damage to the ozone layer matters to organisms that never leave the water?

Q141. Which statement best explains why chlorofluorocarbons are so damaging to the ozone layer in particular?

Q142. Assertion (A): The ozone hole is proof that international environmental agreements are useless. Reason (R): CFC production was frozen and then phased out after 1987, and the ozone layer has since begun to recover.

Q143. Which statement best explains why the thinning of the ozone layer appears most severely over Antarctica?

Q144. A school replaces disposable plates with steel plates that are washed and used again. Which of the three Rs does this best illustrate, and why?

Q145. Consider these statements about how ozone is formed and destroyed in the stratosphere. I. Ultraviolet light splits oxygen molecules into free oxygen atoms. II. Those free atoms join other oxygen molecules to form ozone. III. A single chlorine atom from a CFC can go on to destroy many ozone molecules. IV. Ozone, once formed, is permanent. Which statements are correct?

Q146. Which statement best explains why ozone is a shield high in the atmosphere but a pollutant at ground level?

Q147. Which statement best explains what the recovery of the ozone layer since 1987 demonstrates?

Q148. Why is RECYCLING ranked below reduce and reuse among the three Rs?

Q149. Which statement best explains why a sanitary landfill is lined at the bottom?

Q150. Assertion: The ozone layer is vital for life on land. Reason: It absorbs UV radiation that damages DNA in living cells.

Q151. Assertion: The ozone hole is proof that environmental treaties are useless. Reason: CFC levels kept rising after 1987.

Q152. CFCs are dangerous to ozone specifically because they are:

Q153. Why does the ozone 'hole' open over Antarctica in particular?

Q154. A city's compost plant keeps failing because the waste arriving contains plastic shreds and broken glass. The best remedy is:

Q155. Which shopping choice best applies REDUCE, the first of the three Rs?

Q156. Which statement best explains why vermicomposting is often preferred to plain composting?

Q157. Sanitary landfills are lined at the bottom to:

Q158. Which statement best explains why the open burning of plastic waste is particularly dangerous?

Q159. Case: A school replaces its disposable plates with steel plates that are washed and reused. This action is primarily:

Q160. 'Both biodegradable and non-biodegradable wastes harm the environment, but in different ways.' Explain both sets of harms in detail, and describe the correct management path for each type of waste.

Q161. Design a complete waste-management plan for a school of 1000 students, applying segregation, the 3 Rs, composting and safe disposal. Specify what happens to each major waste stream and how students participate.

Q162. Why is the recovery of the ozone layer called environmental science's greatest success story? Trace the sequence from discovery to recovery, and state two lessons it offers for today's climate-change effort.