Our Environment Part 2: MCQs (Q26–Q50)
🌍 Our Environment – MCQs (Class 10 Science, NCERT)
🔹 Part 2: Questions 26–50
Q26. Which of the following is NOT a greenhouse gas?
A) Carbon dioxide
B) Methane
C) Nitrous oxide
D) Oxygen
Correct Answer: D) Oxygen
Explanation:
- A, B, C → Major greenhouse gases.
- ✅ D) Oxygen does not trap heat, hence not a greenhouse gas.
Q27. Which organisms recycle nutrients back into the soil?
A) Producers
B) Herbivores
C) Decomposers
D) Carnivores
Correct Answer: C) Decomposers
Explanation:
- ✅ C) Decomposers like fungi, bacteria → recycle nutrients.
Q28. Which of the following is a biodegradable waste?
A) Polythene
B) Glass
C) Plastic bottle
D) Vegetable peel
Correct Answer: D) Vegetable peel
Explanation:
- ✅ D) Easily decomposed by microbes.
- A, B, C → Non-biodegradable.
Q29. The sequence of eating and being eaten in an ecosystem is called:
A) Food web
B) Food pyramid
C) Food chain
D) Energy cycle
Correct Answer: C) Food chain
Explanation:
- ✅ C) Linear sequence of energy transfer = food chain.
Q30. The pyramid of energy in an ecosystem is always:
A) Inverted
B) Straight line
C) Upright
D) Irregular
Correct Answer: C) Upright
Explanation:
- ✅ C) Energy decreases at higher trophic levels → upright pyramid.
Q31. Which of the following is NOT an example of natural ecosystem?
A) Forest
B) Lake
C) Garden
D) Pond
Correct Answer: C) Garden
Explanation:
- ✅ C) Garden is man-made, hence artificial.
Q32. Which of the following is NOT true about energy flow in ecosystem?
A) It is unidirectional
B) It is cyclic
C) Energy decreases at each trophic level
D) Only 10% is transferred to next level
Correct Answer: B) It is cyclic
Explanation:
- ✅ B) Matter cycles, energy flows only one way.
Q33. Which of the following causes acid rain?
A) CO₂ and O₂
B) SO₂ and NO₂
C) H₂ and N₂
D) O₃ and O₂
Correct Answer: B) SO₂ and NO₂
Explanation:
- ✅ B) SO₂ + NO₂ dissolve in rainwater → H₂SO₄ & HNO₃.
Q34. The process of breaking down of complex organic matter into simple substances is:
A) Photosynthesis
B) Decomposition
C) Respiration
D) Transpiration
Correct Answer: B) Decomposition
Explanation:
- ✅ B) Decomposers break down dead matter → nutrients.
Q35. Which of the following is NOT a consequence of deforestation?
A) Soil erosion
B) Increase in rainfall
C) Loss of biodiversity
D) Global warming
Correct Answer: B) Increase in rainfall
Explanation:
- ✅ B) Deforestation reduces rainfall instead of increasing it.
Q36. Which trophic level has the least energy?
A) Producers
B) Herbivores
C) Carnivores
D) Top carnivores
Correct Answer: D) Top carnivores
Explanation:
- ✅ D) Energy decreases upward → top carnivores get least.
Q37. Which of the following represents correct order of food chain?
A) Grass → Lion → Deer
B) Grass → Deer → Lion
C) Lion → Grass → Deer
D) Deer → Grass → Lion
Correct Answer: B) Grass → Deer → Lion
Explanation:
- ✅ B) Producer → Herbivore → Carnivore.
Q38. Which of the following is NOT biodegradable?
A) Animal bone
B) Paper
C) Leather bag
D) Aluminium can
Correct Answer: D) Aluminium can
Explanation:
- ✅ D) Aluminium cannot be decomposed naturally.
Q39. Which of the following organisms is both primary and secondary consumer?
A) Cow
B) Lion
C) Human
D) Tiger
Correct Answer: C) Human
Explanation:
- ✅ C) Humans eat plants (primary) and animals (secondary).
Q40. The pyramid of numbers in a grassland ecosystem is:
A) Upright
B) Inverted
C) Irregular
D) Linear
Correct Answer: A) Upright
Explanation:
- ✅ A) Grass > Herbivores > Carnivores → upright pyramid.
Q41. Which of the following is NOT an air pollutant?
A) Carbon dioxide
B) Methane
C) Nitrogen
D) Sulphur dioxide
Correct Answer: C) Nitrogen
Explanation:
- ✅ C) N₂ is inert, not a pollutant.
Q42. Ozone layer protects life on Earth from:
A) Infrared radiation
B) X-rays
C) UV radiation
D) Visible light
Correct Answer: C) UV radiation
Explanation:
- ✅ C) Ozone absorbs harmful UV rays, prevents skin cancer.
Q43. The term “biological magnification” is related to:
A) Increase in population
B) Accumulation of pesticides in food chain
C) Growth of decomposers
D) Increase in crop yield
Correct Answer: B) Accumulation of pesticides in food chain
Explanation:
- ✅ B) Toxins (DDT) increase concentration at higher trophic levels.
Q44. Which of the following is the primary cause of global warming?
A) Deforestation
B) Burning fossil fuels
C) Greenhouse gases
D) All of these
Correct Answer: D) All of these
Explanation:
- ✅ D) All contribute to increased greenhouse gases.
Q45. The maximum concentration of harmful chemicals in a food chain occurs in:
A) Producers
B) Primary consumers
C) Secondary consumers
D) Tertiary consumers
Correct Answer: D) Tertiary consumers
Explanation:
- ✅ D) Biological magnification → highest in top consumers.
Q46. Which of the following does NOT cause water pollution?
A) Industrial effluents
B) Oil spills
C) Plastic waste
D) Plant leaves
Correct Answer: D) Plant leaves
Explanation:
- ✅ D) Plant leaves are biodegradable and do not cause pollution.
Q47. Which is NOT a greenhouse gas?
A) Carbon dioxide
B) Methane
C) Water vapour
D) Oxygen
Correct Answer: D) Oxygen
Explanation:
- ✅ D) O₂ does not contribute to greenhouse effect.
Q48. Which of these practices leads to soil pollution?
A) Crop rotation
B) Excessive use of pesticides
C) Organic farming
D) Composting
Correct Answer: B) Excessive use of pesticides
Explanation:
- ✅ B) Pesticides contaminate soil, accumulate in food chain.
Q49. Which organisms help in decomposition of waste?
A) Plants
B) Bacteria and fungi
C) Lions and tigers
D) Insects only
Correct Answer: B) Bacteria and fungi
Explanation:
- ✅ B) Microbes decompose organic matter into nutrients.
Q50. Which of the following can control ozone depletion?
A) Use of CFC-free refrigerators
B) Reduce plastic use
C) Reduce use of coal
D) Stop using pesticides
Correct Answer: A) Use of CFC-free refrigerators
Explanation:
- ✅ A) Limiting CFCs is the direct solution for ozone layer protection.
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