🌍 Our Environment – MCQs (Class 10 Science, NCERT)

🔹 Part 3: Questions 51–75

Q51. Which of the following is an example of a decomposer?

A) Grasshopper
B) Mushroom
C) Lion
D) Goat

Correct Answer: B) Mushroom

Explanation:

• A) Grasshopper → Herbivore (primary consumer).
• ✅ B) Mushroom → Fungi, decomposer.
• C, D → Consumers, not decomposers.

Q52. Which of the following organisms occupy more than one trophic level in a food web?

A) Cow
B) Human
C) Lion
D) Tiger

Correct Answer: B) Human

Explanation:

• ✅ B) Humans are omnivores → eat plants & animals.

Q53. Which gas is produced in large amounts by burning fossil fuels and causes global warming?

A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Hydrogen

Correct Answer: B) Carbon dioxide

Explanation:

• ✅ B) CO₂ traps heat → greenhouse effect.

Q54. Which of the following is NOT an example of non-biodegradable waste?

A) DDT
B) Plastics
C) Polythene
D) Vegetable waste

Correct Answer: D) Vegetable waste

Explanation:

• ✅ D) Vegetable waste decomposes naturally, hence biodegradable.

Q55. Which process is responsible for returning carbon dioxide to atmosphere in the carbon cycle?

A) Photosynthesis
B) Respiration
C) Combustion
D) Both B and C

Correct Answer: D) Both B and C

Explanation:

• ✅ D) Respiration & burning release CO₂; photosynthesis absorbs it.

Q56. In a forest food chain, tigers are:

A) Producers
B) Herbivores
C) Primary consumers
D) Tertiary consumers

Correct Answer: D) Tertiary consumers

Explanation:

• ✅ D) Tigers eat herbivores/carnivores → top level.

Q57. Which of the following will cause maximum damage to environment if disposed openly?

A) Fruit peel
B) Glass bottle
C) Paper
D) Cotton cloth

Correct Answer: B) Glass bottle

Explanation:

• ✅ B) Glass is non-biodegradable, persists for centuries.

Q58. Which step is NOT useful in controlling plastic waste?

A) Recycling
B) Reuse
C) Burning in open air
D) Reduction in use

Correct Answer: C) Burning in open air

Explanation:

• ✅ C) Burning → toxic gases. Reuse, reduce, recycle are safe.

Q59. The concept of 3Rs in waste management stands for:

A) Reduce, Reuse, Recycle
B) Reuse, Rebuild, Restore
C) Reduce, Reproduce, Recycle
D) Reuse, Reduce, Reform

Correct Answer: A) Reduce, Reuse, Recycle

Explanation:

• ✅ A) 3Rs = eco-friendly waste management principle.

Q60. Which chemical causes biological magnification in aquatic food chains?

A) CO₂
B) DDT
C) Ozone
D) Methane

Correct Answer: B) DDT

Explanation:

• ✅ B) DDT pesticide accumulates at higher trophic levels.

Q61. Which of the following organisms can fix nitrogen naturally?

A) Rhizobium
B) Lion
C) Fungi
D) Human

Correct Answer: A) Rhizobium

Explanation:

• ✅ A) Rhizobium bacteria fix nitrogen in root nodules.

Q62. Which of these activities contributes most to ozone depletion?

A) Burning coal
B) Refrigerants and aerosols
C) Automobile smoke
D) Forest fires

Correct Answer: B) Refrigerants and aerosols

Explanation:

• ✅ B) CFCs in refrigerants release chlorine → destroy ozone.

Q63. Which statement about energy flow in an ecosystem is correct?

A) Energy cycles
B) Energy decreases at each level
C) Energy is fully conserved
D) Energy flows backward

Correct Answer: B) Energy decreases at each level

Explanation:

• ✅ B) Only 10% passes on, rest lost as heat.

Q64. Which of the following is an abiotic factor?

A) Trees
B) Bacteria
C) Temperature
D) Insects

Correct Answer: C) Temperature

Explanation:

• ✅ C) Abiotic = non-living factors like air, water, soil, temperature.

Q65. Which of the following is NOT a renewable resource?

A) Sunlight
B) Air
C) Coal
D) Water

Correct Answer: C) Coal

Explanation:

• ✅ C) Coal is limited, takes millions of years to form.

Q66. In a pond ecosystem, which forms the producer level?

A) Fish
B) Insects
C) Phytoplankton
D) Frogs

Correct Answer: C) Phytoplankton

Explanation:

• ✅ C) Microscopic plants in water carry out photosynthesis.

Q67. The accumulation of harmful chemicals in organisms across trophic levels is called:

A) Eutrophication
B) Biological magnification
C) Decomposition
D) Symbiosis

Correct Answer: B) Biological magnification

Explanation:

• ✅ B) Toxins like DDT concentrate at higher levels.

Q68. Which is NOT a harmful effect of global warming?

A) Melting of glaciers
B) Rise in sea level
C) Increase in biodiversity
D) Climate change

Correct Answer: C) Increase in biodiversity

Explanation:

• ✅ C) Biodiversity decreases, not increases, due to global warming.

Q69. The ozone hole is observed mostly over:

A) Africa
B) Antarctica
C) Asia
D) Europe

Correct Answer: B) Antarctica

Explanation:

• ✅ B) Ozone hole → severe in polar regions.

Q70. Which of the following is an artificial ecosystem?

A) Pond
B) River
C) Aquarium
D) Forest

Correct Answer: C) Aquarium

Explanation:

• ✅ C) Aquarium is man-made, controlled ecosystem.

Q71. Which group of organisms always forms the first trophic level?

A) Herbivores
B) Producers
C) Decomposers
D) Carnivores

Correct Answer: B) Producers

Explanation:

• ✅ B) Green plants trap solar energy → first level.

Q72. The maximum number of individuals in a pyramid of numbers is found at:

A) Top carnivores
B) Primary consumers
C) Producers
D) Decomposers

Correct Answer: C) Producers

Explanation:

• ✅ C) Plants are most numerous → base of pyramid.

Q73. Which one of the following is an example of primary consumer?

A) Lion
B) Grasshopper
C) Snake
D) Peacock

Correct Answer: B) Grasshopper

Explanation:

• ✅ B) Herbivore, eats grass directly.

Q74. Which activity directly adds carbon dioxide to the atmosphere?

A) Photosynthesis
B) Respiration
C) Condensation
D) Water cycle

Correct Answer: B) Respiration

Explanation:

• ✅ B) Respiration releases CO₂, photosynthesis absorbs it.

Q75. Which of the following is a natural cause of air pollution?

A) Forest fire
B) Burning coal
C) Vehicle exhaust
D) Industrial gases

Correct Answer: A) Forest fire

Explanation:

• ✅ A) Forest fire naturally releases CO₂, smoke.

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