Class 10 Science Our Environment MCQ

Class 10 Science Our Environment MCQ

Class 10 Science — Chapter 13: Our Environment Question Bank

A. MCQs — Choose the Correct Answer

1. Which combination correctly represents the two major components of an ecosystem?

(a) Producers and consumers
(b) Biotic and abiotic components
(c) Plants and animals
(d) Food chains and food webs

2. Which organisms occupy the first trophic level?

(a) Herbivores
(b) Carnivores
(c) Producers
(d) Decomposers

3. In the food chain
Grass → Grasshopper → Frog → Snake,
the frog represents the:

(a) First trophic level
(b) Second trophic level
(c) Third trophic level
(d) Fourth trophic level

4. Which organisms are mainly responsible for breaking down dead remains and wastes?

(a) Producers
(b) Herbivores
(c) Decomposers
(d) Carnivores

5. Approximately what fraction of the available organic matter/energy is transferred to the next trophic level on average?

(a) 1%
(b) 5%
(c) 10%
(d) 50%

6. Energy flow through an ecosystem is:

(a) Circular
(b) Bidirectional
(c) Unidirectional
(d) Random

7. Several interconnected food chains together form a:

(a) Trophic level
(b) Food web
(c) Producer level
(d) Decomposer cycle

8. The progressive accumulation of certain harmful, non-degradable chemicals at higher trophic levels is called:

(a) Decomposition
(b) Biological magnification
(c) Photosynthesis
(d) Nutrient cycling

9. The chemical group specifically discussed in relation to ozone depletion is:

(a) CFCs
(b) Proteins
(c) Carbohydrates
(d) Enzymes

10. The major protective role of atmospheric ozone is to:

(a) Produce food for plants
(b) Absorb harmful ultraviolet radiation
(c) Increase soil fertility
(d) Decompose plastic waste

11. A material that can be broken down by biological processes is:

(a) Non-biodegradable
(b) Biodegradable
(c) Synthetic
(d) Inert

12. Which statement is correct?

(a) Energy increases at higher trophic levels.
(b) Energy flow returns from consumers to producers.
(c) Energy available decreases at successive trophic levels.
(d) Food chains can continue indefinitely without energy loss.

B. Assertion–Reason Questions

Choose the correct option:

A. Both Assertion and Reason are true, and Reason correctly explains Assertion.
B. Both are true, but Reason does not correctly explain Assertion.
C. Assertion is true, but Reason is false.
D. Assertion is false, but Reason is true.

13.
Assertion: Food chains generally contain only a few trophic levels.
Reason: A large amount of energy is lost at each trophic level.

14.
Assertion: Decomposers are important components of an ecosystem.
Reason: They break down dead matter and help return simpler substances to the environment.

15.
Assertion: Energy flow in an ecosystem is unidirectional.
Reason: Energy that passes to a higher trophic level does not return to the previous level.

16.
Assertion: Biological magnification can be greater at higher trophic levels.
Reason: Some harmful chemicals are not easily degraded and can accumulate through the food chain.

17.
Assertion: Ozone in the upper atmosphere is environmentally important.
Reason: It helps shield Earth from harmful UV radiation.

C. Fill in the Blanks

18. The living components of an ecosystem are called __________ components.

19. Soil, temperature and rainfall are examples of __________ factors.

20. Green plants that manufacture food through photosynthesis are called __________.

21. Organisms that depend directly or indirectly on producers for food are called __________.

22. Bacteria and fungi commonly act as __________ in an ecosystem.

23. Each feeding position in a food chain is known as a __________ level.

24. Producers occupy the __________ trophic level.

25. The average transfer of organic matter/energy from one trophic level to the next is about __________%.

26. A network of interconnected food chains is called a food __________.

27. The increase in concentration of certain harmful chemicals along successive trophic levels is called biological __________.

28. Ozone has the molecular formula __________.

29. CFC stands for __________.

30. Materials that can be broken down by biological processes are called __________.

D. True or False

31. A garden can function as an artificial ecosystem.

32. Producers obtain their food by consuming herbivores.

33. Decomposers help in the recycling of materials in an ecosystem.

34. Energy available generally increases as we move to higher trophic levels.

35. A food web consists of interconnected food chains.

36. Biological magnification is associated with certain harmful, non-degradable chemicals.

37. Ozone in the higher atmosphere helps protect organisms from harmful UV radiation.

38. All waste materials are biodegradable.

E. Match the Following

Column AColumn B
39. ProducersA. Network of food chains
40. DecomposersB. First trophic level
41. Food webC. Break down dead matter
42. OzoneD. Protects against UV radiation
43. Biological magnificationE. Increasing concentration of certain harmful chemicals

F. Very Short Answer Questions

44. What is an ecosystem?

45. Name two abiotic components of an ecosystem.

46. What is a producer?

47. What is meant by a trophic level?

48. Why are decomposers important?

49. What is a food web?

50. Why is energy flow in an ecosystem called unidirectional?

51. What is biological magnification?

52. What is ozone?

53. What is meant by a biodegradable substance?

54. What is a non-biodegradable substance?

G. Short Answer Questions

55. Differentiate between biotic and abiotic components of an ecosystem with examples.

56. Explain the roles of producers, consumers and decomposers in an ecosystem.

57. Explain why the amount of usable energy decreases as we move from one trophic level to the next.

58. Distinguish between a food chain and a food web.

59. Why are food chains generally limited to a few trophic levels?

60. Explain how harmful chemicals can enter a food chain and become concentrated at higher trophic levels.

61. Why is the ozone layer important even though ozone can be harmful at ground level?

62. Differentiate between biodegradable and non-biodegradable substances.

63. How can increasing use of disposable products contribute to environmental problems?

H. Long Answer / Competency-Based Questions

64. Consider the food chain:

Grass → Grasshopper → Frog → Snake → Eagle

Answer the following:

  1. Identify the producer.
  2. Identify the primary consumer.
  3. Which organism represents the third trophic level?
  4. Which organism occupies the highest trophic level in this chain?
  5. Explain why the amount of available energy decreases along this chain.

65. A pesticide enters a pond and is absorbed by aquatic plants. Small animals feed on these plants, fish eat the small animals, and a bird feeds on the fish.

Answer:

  1. How can the pesticide move through the food chain?
  2. What is this phenomenon called when the concentration increases at successive trophic levels?
  3. Which organism is likely to receive the highest concentration among those listed?
  4. Why can such chemicals create environmental concerns?

66. A student observes that leaves and food waste disappear gradually when placed in moist soil, while plastic remains for a much longer period.

Answer:

  1. Which type of waste can be biologically decomposed?
  2. Which type is likely to persist?
  3. Why do different materials behave differently?
  4. State one environmental problem associated with persistent non-biodegradable waste.

67. A town produces increasing quantities of disposable packaging and other waste.

Answer:

  1. Why can changes in lifestyle increase waste generation?
  2. Why is non-biodegradable packaging particularly problematic?
  3. Suggest two responsible approaches to waste management.
  4. Explain why simply throwing waste away does not solve the problem.

I. Case-Based Questions

Case Study 1 — Ecosystem

A school maintains a small garden containing grasses, flowering plants, insects, frogs and birds. The organisms interact with one another and are also influenced by sunlight, soil, water and temperature.

68. The garden represents a:

(a) Natural ecosystem
(b) Artificial ecosystem
(c) Food chain only
(d) Trophic level

69. Which of the following is an abiotic factor?

(a) Frog
(b) Bird
(c) Soil
(d) Grass

70. The plants in the garden are primarily:

(a) Consumers
(b) Producers
(c) Decomposers
(d) Parasites

71. Why can the garden be considered an ecosystem?

Case Study 2 — Energy Transfer

In an ecosystem, plants capture solar energy and store it as chemical energy. Herbivores obtain energy by eating plants, while carnivores obtain energy by feeding on other animals. Only a fraction of the available energy is passed to the next trophic level.

72. What is the direction of energy flow?

(a) Consumers → producers
(b) Producers → consumers
(c) Decomposers → Sun
(d) Consumers → Sun

73. Why does a food chain usually not contain many trophic levels?

74. What happens to much of the energy that is not transferred to the next level?

Case Study 3 — Ozone

Certain synthetic chemicals were associated with the reduction of atmospheric ozone. The ozone layer is important because it helps protect organisms from harmful ultraviolet radiation.

75. What is the chemical formula of ozone?

(a) O
(b) O₂
(c) O₃
(d) CO₂

76. What type of radiation does atmospheric ozone help block?

77. Name the group of synthetic chemicals discussed in connection with ozone depletion.

78. Why is ozone depletion an environmental concern?

J. HOTS / Thinking Questions

79. If decomposers disappeared from an ecosystem, what major change would you expect in the recycling of materials? Explain.

80. Why would removing organisms from one trophic level potentially affect organisms at other trophic levels?

81. Why does a food web provide a better representation of many natural feeding relationships than a simple food chain?

82. Suppose a harmful chemical cannot be degraded easily. Why might organisms at higher trophic levels face greater exposure?

83. If all waste produced by humans were biodegradable, would waste disposal automatically stop being an environmental concern? Give a reasoned answer.

K. Answer Key

MCQs

  1. (b)
  2. (c)
  3. (c)
  4. (c)
  5. (c)
  6. (c)
  7. (b)
  8. (b)
  9. (a)
  10. (b)
  11. (b)
  12. (c)

Assertion–Reason

  1. A
  2. A
  3. A
  4. A
  5. A

Fill in the Blanks

  1. biotic
  2. abiotic
  3. producers
  4. consumers
  5. decomposers
  6. trophic
  7. first
  8. 10
  9. web
  10. magnification
  11. O₃
  12. chlorofluorocarbon
  13. biodegradable

True / False

  1. True
  2. False
  3. True
  4. False
  5. True
  6. True
  7. True
  8. False

Match the Following

  1. B
  2. C
  3. A
  4. D
  5. E

Very Short Answers — Key Points

  1. An ecosystem is a system in which living organisms interact with one another and with their physical surroundings.
  2. Any two: soil, temperature, rainfall, wind, minerals.
  3. An organism that makes its own food, generally through photosynthesis.
  4. A trophic level is a feeding position in a food chain.
  5. They break down dead matter and wastes and help recycle materials.
  6. A network of interconnected food chains.
  7. Because energy moves from one trophic level to the next and does not return to the previous level.
  8. The progressive increase in concentration of certain harmful, non-degradable chemicals at successive trophic levels.
  9. Ozone is a molecule made of three oxygen atoms (O₃).
  10. A substance that can be broken down by biological processes.
  11. A substance that is not readily broken down by biological processes.

Short / Long Answers — Key Points

55.
Biotic components are living parts of an ecosystem; abiotic components are non-living physical factors. Examples: plants/animals versus soil/temperature.

56.
Producers introduce energy into the ecosystem by making food. Consumers obtain food directly or indirectly from producers. Decomposers break down dead matter and wastes and help recycle materials.

57.
Energy is lost during life processes and largely as heat. Consequently, only a fraction is transferred to the next trophic level.

58.
A food chain represents one feeding pathway, whereas a food web connects several food chains.

59.
Energy decreases greatly at each trophic level, leaving too little usable energy to support many additional levels.

60.
Chemicals can enter plants or aquatic organisms from contaminated soil or water. They can then move through feeding relationships and become increasingly concentrated at higher trophic levels.

61.
Upper-atmosphere ozone absorbs harmful UV radiation, thereby providing protection to organisms on Earth.

62.
Biodegradable materials can be broken down biologically; non-biodegradable materials are not readily broken down and may persist for long periods.

63.
Disposable products and non-biodegradable packaging can increase the volume of waste and make environmental management more difficult.

⭐ High-Priority Questions for Exam Revision

If time is limited, prepare these first:

1. Define ecosystem and distinguish biotic and abiotic components.

2. Explain producers, consumers and decomposers.

3. What are trophic levels? Explain with a suitable food chain.

4. Explain the 10% transfer concept and why food chains are short.

5. Differentiate between food chain and food web.

6. Explain biological magnification.

7. Explain the importance of the ozone layer and the problem of its depletion.

8. Differentiate between biodegradable and non-biodegradable waste.

9. Explain how human activities affect the environment.

10. Solve a food-chain question involving trophic levels, energy transfer and biological magnification.