CBSE Class 12 Biology MCQs with Answers & Explanations – Environmental Issues (NCERT Based)

Unit V: Ecology and Environment | Chapter 16: Environmental Issues

CBSE Class 12 Biology Chapter 16 MCQs with Answers and Explanations – Environmental Issues (NCERT)

Course & Examination Details

• Course: CBSE Class 12 Biology
• Unit: Unit V – Ecology and Environment
• Chapter: Chapter 16 – Environmental Issues
• Board: Central Board of Secondary Education (CBSE)
• Syllabus Base: Strictly as per NCERT Textbook
• Exam Relevance: CBSE Class 12 Board Exams, Pre-Boards, Unit Tests

Multiple Choice Questions (MCQs) with Answers & Explanations

(50 MCQs prepared strictly as per NCERT concepts, with clear explanations for concept building)

Section A: Air Pollution and Its Control (Q1–Q10)

Q1. Air pollution refers to:
A. Presence of only smoke in air
B. Increase in oxygen concentration
C. Presence of harmful substances in air
D. Presence of dust only

Answer: C
Explanation: Air pollution is the presence of harmful solid, liquid, or gaseous substances in air at injurious concentrations.

Q2. Which gas is produced by incomplete combustion of fossil fuels?
A. CO₂
B. CO
C. SO₂
D. NO₂

Answer: B
Explanation: Carbon monoxide is formed due to incomplete combustion and reduces oxygen transport in blood.

Q3. Which pollutant causes irritation of eyes and respiratory tract?
A. Carbon dioxide
B. Particulate matter
C. Nitrogen
D. Oxygen

Answer: B
Explanation: Fine particulate matter penetrates lungs and irritates respiratory passages.

Q4. Smog is a combination of:
A. Smoke and dust
B. Fog and smoke
C. Fog and ozone
D. Smoke and carbon monoxide

Answer: B
Explanation: Smog is a mixture of smoke and fog commonly found in polluted urban areas.

Q5. Acid rain is mainly caused by:
A. CO and CO₂
B. SO₂ and NOₓ
C. O₃ and CO
D. Methane and ammonia

Answer: B
Explanation: Sulphur dioxide and nitrogen oxides react with moisture to form acids.

Q6. Which device removes particulate matter from industrial emissions?
A. Scrubber
B. Catalytic converter
C. Electrostatic precipitator
D. Incinerator

Answer: C
Explanation: Electrostatic precipitators trap particulate pollutants using electric charges.

Q7. Catalytic converters are used to reduce:
A. Solid waste
B. Water pollution
C. Automobile emissions
D. Noise pollution

Answer: C
Explanation: Catalytic converters reduce toxic gases from vehicle exhausts.

Q8. Which fuel is considered environment-friendly for vehicles?
A. Petrol
B. Diesel
C. Coal
D. CNG

Answer: D
Explanation: CNG produces fewer pollutants than petrol or diesel.

Q9. Photochemical smog is formed due to reaction of pollutants with:
A. Rainwater
B. Oxygen
C. Sunlight
D. Nitrogen

Answer: C
Explanation: Sunlight triggers reactions between nitrogen oxides and hydrocarbons.

Q10. Which pollutant contributes to global warming?
A. Oxygen
B. Carbon dioxide
C. Nitrogen
D. Helium

Answer: B
Explanation: Carbon dioxide is a major greenhouse gas.

Section B: Water Pollution and Its Control (Q11–Q20)

Q11. Water pollution occurs due to:
A. Excess rainfall
B. Harmful substances in water
C. Increase in water level
D. Presence of oxygen

Answer: B
Explanation: Contaminants degrade water quality and harm life.

Q12. Domestic sewage mainly contains:
A. Heavy metals
B. Organic waste
C. Radioactive material
D. Oil

Answer: B
Explanation: Sewage has organic matter that depletes oxygen.

Q13. Eutrophication is caused by excess of:
A. Oxygen
B. Heavy metals
C. Nutrients
D. Carbon dioxide

Answer: C
Explanation: Excess nitrates and phosphates cause algal blooms.

Q14. Which effect of eutrophication kills fish?
A. Increased oxygen
B. Oxygen depletion
C. Increased pH
D. Salinity

Answer: B
Explanation: Decomposition of algae consumes dissolved oxygen.

Q15. Biomagnification refers to:
A. Increase in population
B. Accumulation of toxins
C. Rapid reproduction
D. Decrease in biomass

Answer: B
Explanation: Toxic substances increase in concentration at higher trophic levels.

Q16. Which disease is water-borne?
A. Asthma
B. Tuberculosis
C. Cholera
D. Cancer

Answer: C
Explanation: Cholera spreads through contaminated water.

Q17. Industrial effluents should be treated to remove:
A. Oxygen
B. Nutrients
C. Toxic chemicals
D. Water

Answer: C
Explanation: Industrial wastes contain harmful chemicals.

Q18. Thermal pollution is caused by:
A. Cold water discharge
B. Hot water discharge
C. Oil spills
D. Plastic waste

Answer: B
Explanation: Hot water reduces dissolved oxygen levels.

Q19. Which detergent is preferred to reduce water pollution?
A. Synthetic
B. Non-biodegradable
C. Biodegradable
D. Strong alkaline

Answer: C
Explanation: Biodegradable detergents decompose easily.

Q20. Oil spills mainly affect:
A. Terrestrial life
B. Marine ecosystems
C. Forest ecosystems
D. Deserts

Answer: B
Explanation: Oil spills block oxygen exchange in water.

Section C: Solid Waste Management (Q21–Q30)

Q21. Solid waste includes:
A. Sewage
B. Garbage
C. Industrial gases
D. Wastewater

Answer: B
Explanation: Solid waste includes discarded solid materials.

Q22. Composting is used for:
A. Plastic waste
B. E-waste
C. Biodegradable waste
D. Radioactive waste

Answer: C
Explanation: Organic waste decomposes to manure.

Q23. Recycling helps in:
A. Increasing waste
B. Resource conservation
C. Pollution increase
D. Energy wastage

Answer: B
Explanation: Recycling saves raw materials and energy.

Q24. Sanitary landfills are used for:
A. Open dumping
B. Safe waste disposal
C. Waste burning
D. Wastewater treatment

Answer: B
Explanation: They prevent soil and water contamination.

Q25. Incineration involves:
A. Decomposition
B. Burial
C. Burning
D. Recycling

Answer: C
Explanation: Incineration burns waste at high temperature.

Q26. E-waste is hazardous because it contains:
A. Nutrients
B. Toxic metals
C. Organic matter
D. Water

Answer: B
Explanation: Metals like lead and mercury are toxic.

Q27. Waste segregation is important to:
A. Increase garbage
B. Reduce recycling
C. Improve waste management
D. Spread disease

Answer: C
Explanation: Segregation aids proper disposal and recycling.

Q28. Which is an example of hazardous waste?
A. Kitchen waste
B. Paper
C. Biomedical waste
D. Vegetable peels

Answer: C
Explanation: Biomedical waste contains pathogens.

Q29. Plastic waste mainly causes:
A. Soil enrichment
B. Water purification
C. Environmental pollution
D. Oxygen release

Answer: C
Explanation: Plastics are non-biodegradable.

Q30. Best way to reduce waste generation is:
A. Recycling only
B. Reuse and reduce
C. Incineration
D. Landfilling

Answer: B
Explanation: Reducing and reusing minimize waste at source.

Section D: Agrochemicals, Climate Change & Deforestation (Q31–Q50)

Q31. Agrochemicals include:
A. Medicines
B. Fertilizers and pesticides
C. Fuels
D. Plastics

Answer: B
Explanation: Agrochemicals are used to increase crop yield.

Q32. Excessive use of pesticides causes:
A. Soil fertility increase
B. Biomagnification
C. Oxygen enrichment
D. Reduced pollution

Answer: B
Explanation: Toxins accumulate at higher trophic levels.

Q33. Which chemical is associated with biomagnification in NCERT?
A. Urea
B. DDT
C. Ammonia
D. Carbon dioxide

Answer: B
Explanation: DDT concentration increases along food chains.

Q34. Radioactive wastes are produced by:
A. Thermal plants
B. Hydropower plants
C. Nuclear plants
D. Wind farms

Answer: C
Explanation: Nuclear reactions generate radioactive wastes.

Q35. Radioactive wastes are dangerous because they:
A. Are biodegradable
B. Emit radiation
C. Are non-toxic
D. Decompose quickly

Answer: B
Explanation: Radiation causes genetic damage and cancer.

Q36. Global warming is caused due to:
A. Reduced greenhouse gases
B. Enhanced greenhouse effect
C. Ozone formation
D. Increased oxygen

Answer: B
Explanation: Excess greenhouse gases trap more heat.

Q37. Which is a greenhouse gas?
A. Oxygen
B. Nitrogen
C. Carbon dioxide
D. Helium

Answer: C
Explanation: CO₂ traps heat in atmosphere.

Q38. One effect of global warming is:
A. Glacier formation
B. Sea level rise
C. Reduced rainfall everywhere
D. Decreased temperature

Answer: B
Explanation: Melting glaciers raise sea levels.

Q39. Ozone layer depletion is caused by:
A. CO₂
B. Methane
C. CFCs
D. Nitrogen

Answer: C
Explanation: CFCs destroy ozone molecules.

Q40. Ozone layer protects Earth from:
A. Infrared rays
B. Gamma rays
C. Ultraviolet rays
D. X-rays

Answer: C
Explanation: Ozone absorbs harmful UV radiation.

Q41. Increased UV radiation causes:
A. Reduced cancer
B. Skin cancer
C. Better vision
D. Crop growth

Answer: B
Explanation: UV damages skin cells.

Q42. Deforestation leads to:
A. Climate stability
B. Soil conservation
C. Biodiversity loss
D. Oxygen increase

Answer: C
Explanation: Forest removal destroys habitats.

Q43. Main cause of deforestation is:
A. Photosynthesis
B. Afforestation
C. Agriculture expansion
D. Rainfall

Answer: C
Explanation: Land is cleared for farming.

Q44. Which practice helps control deforestation?
A. Mining
B. Urbanization
C. Afforestation
D. Industrialization

Answer: C
Explanation: Planting trees restores forest cover.

Q45. Deforestation increases:
A. CO₂ absorption
B. Oxygen production
C. Atmospheric CO₂
D. Rainfall

Answer: C
Explanation: Fewer trees absorb less CO₂.

Q46. Which is the safest method to dispose radioactive waste?
A. Open dumping
B. Incineration
C. Deep geological burial
D. Composting

Answer: C
Explanation: It isolates waste from biosphere.

Q47. Integrated pest management aims to:
A. Increase pesticide use
B. Eliminate all insects
C. Reduce chemical use
D. Kill soil microbes

Answer: C
Explanation: It uses biological and mechanical controls.

Q48. Climate change affects biodiversity by:
A. Increasing habitats
B. Stabilizing ecosystems
C. Causing extinctions
D. Improving adaptation

Answer: C
Explanation: Rapid changes exceed species tolerance.

Q49. Best long-term solution to environmental issues is:
A. Industrial expansion
B. Sustainable development
C. Resource exploitation
D. Urbanization

Answer: B
Explanation: Sustainability balances development and environment.

Q50. Environmental conservation is important because it:
A. Slows growth
B. Maintains ecological balance
C. Reduces life expectancy
D. Stops evolution

Answer: B
Explanation: Conservation ensures ecosystem stability and survival.

CBSE Exam Tip

These 50 MCQs are ideal for objective sections, revision, and concept reinforcement, strictly aligned with NCERT Class 12 Biology Chapter 16 – Environmental Issues.

Targeting Exams

• CBSE Class 12 Biology Board Examination

• CBSE Pre-Board & Unit Tests

• School Internal Assessments

• NEET (UG) – Ecology & Environment Conceptual MCQs

• Other Class 12 Medical Entrance Examinations

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