CBSE Class 12 Biology Short Answer Questions – Environmental Issues (NCERT Based)

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

CBSE Class 12 Biology Chapter 16 Short Answer Questions – 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 Examinations (2–3 Mark Questions)

Short Answer Type Questions (60–80 Words Each)

(Prepared strictly as per NCERT syllabus and CBSE answer-writing standards)

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

Q1. Define air pollution and mention its major sources.

Ans:
Air pollution refers to the presence of harmful solid, liquid, or gaseous substances in the atmosphere at concentrations injurious to living organisms and property. Major sources include automobile exhausts, industrial emissions, burning of fossil fuels, thermal power plants, and domestic fuel combustion.

Q2. What are the major effects of air pollution on human health?

Ans:
Air pollution causes respiratory diseases such as asthma, bronchitis, and lung cancer. Pollutants like carbon monoxide reduce oxygen transport in blood, while particulate matter damages lungs, eyes, and cardiovascular health.

Q3. Explain the formation and effects of smog.

Ans:
Smog is formed by the interaction of smoke, fog, and pollutants like nitrogen oxides and hydrocarbons under sunlight. It reduces visibility, irritates eyes, and causes breathing problems, especially in urban areas.

Q4. What is acid rain and how does it affect the environment?

Ans:
Acid rain results from sulphur dioxide and nitrogen oxides reacting with atmospheric moisture to form sulphuric and nitric acids. It damages crops, aquatic life, soil fertility, and corrodes buildings and monuments.

Q5. Describe any two methods to control air pollution.

Ans:
Air pollution can be controlled by using cleaner fuels such as CNG and LPG and installing electrostatic precipitators in industries. Afforestation and use of catalytic converters in vehicles also reduce emissions.

Q6. What is the role of catalytic converters in automobiles?

Ans:
Catalytic converters convert harmful exhaust gases like carbon monoxide, nitrogen oxides, and hydrocarbons into less toxic substances, reducing air pollution from vehicles.

Q7. Why is particulate matter considered dangerous?

Ans:
Particulate matter penetrates deep into lungs, causing respiratory diseases, reduced lung function, and cardiovascular problems, especially in children and elderly people.

Q8. How does air pollution contribute to global warming?

Ans:
Air pollutants such as carbon dioxide and methane trap heat in the atmosphere, enhancing the greenhouse effect and leading to global warming.

Q9. What is photochemical smog?

Ans:
Photochemical smog is formed by the reaction of sunlight with nitrogen oxides and hydrocarbons, producing ozone and toxic compounds harmful to health and vegetation.

Q10. Mention two long-term solutions to reduce air pollution.

Ans:
Promotion of renewable energy sources and strict enforcement of emission standards are effective long-term solutions to reduce air pollution.

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

Q11. Define water pollution and list its main sources.

Ans:
Water pollution is contamination of water bodies by harmful substances, making water unfit for use. Major sources include domestic sewage, industrial effluents, agricultural runoff, and oil spills.

Q12. Explain eutrophication and its consequences.

Ans:
Eutrophication is nutrient enrichment of water bodies due to excess fertilizers. It causes algal blooms, reduces dissolved oxygen, and leads to death of aquatic organisms.

Q13. What is bioaccumulation? How is it harmful?

Ans:
Bioaccumulation is the accumulation of toxic substances in organisms over time. It leads to health hazards and biomagnification across food chains.

Q14. How does sewage affect aquatic ecosystems?

Ans:
Untreated sewage increases organic matter, depletes dissolved oxygen, promotes pathogen growth, and disrupts aquatic ecosystems.

Q15. Describe two measures to control water pollution.

Ans:
Water pollution can be controlled by treating sewage and industrial effluents before discharge and minimizing use of chemical fertilizers and detergents.

Q16. What are water-borne diseases? Name two.

Ans:
Water-borne diseases are illnesses transmitted through contaminated water. Examples include cholera and typhoid.

Q17. How do oil spills affect marine life?

Ans:
Oil spills form a surface layer preventing oxygen exchange, poisoning marine organisms and disrupting food chains.

Q18. What role do microorganisms play in sewage treatment?

Ans:
Microorganisms break down organic matter during sewage treatment, reducing pollution load and pathogens.

Q19. Why are biodegradable detergents preferred?

Ans:
They decompose easily, reduce water pollution, and prevent accumulation of toxic residues.

Q20. Explain thermal pollution.

Ans:
Thermal pollution occurs when industries release hot water into water bodies, reducing oxygen levels and harming aquatic organisms.

Section C: Solid Waste Management (Q21–Q30)

Q21. What is solid waste? Give examples.

Ans:
Solid waste includes discarded materials like household garbage, industrial waste, biomedical waste, and electronic waste.

Q22. Why is improper waste disposal harmful?

Ans:
It causes land and water pollution, spreads diseases, and releases toxic gases.

Q23. Explain composting as a waste management method.

Ans:
Composting involves microbial decomposition of biodegradable waste into nutrient-rich manure, reducing landfill load.

Q24. What is recycling? Mention its importance.

Ans:
Recycling converts waste materials into reusable products, conserving resources and reducing pollution.

Q25. What are sanitary landfills?

Ans:
Sanitary landfills are engineered sites for safe disposal of solid waste to prevent environmental contamination.

Q26. What is incineration? State one disadvantage.

Ans:
Incineration is burning of waste at high temperatures. It can release toxic gases if not properly managed.

Q27. Why is waste segregation essential?

Ans:
Segregation facilitates recycling, composting, and safe disposal of hazardous waste.

Q28. What problems are caused by e-waste?

Ans:
E-waste contains toxic metals that contaminate soil and water, posing health hazards.

Q29. How can households reduce solid waste generation?

Ans:
By practicing reuse, composting, recycling, and reducing plastic use.

Q30. What is the role of government in waste management?

Ans:
Government enforces waste management rules and promotes sustainable practices.

Section D: Agrochemicals, Radioactive Wastes, Climate Issues (Q31–Q50)

Q31. What are agrochemicals and why are they used?

Ans:
Agrochemicals are fertilizers and pesticides used to increase crop productivity.

Q32. How do agrochemicals affect soil health?

Ans:
Excessive use degrades soil fertility and kills beneficial microorganisms.

Q33. Explain biomagnification with an example.

Ans:
Biomagnification is increasing concentration of toxins at higher trophic levels, such as DDT in birds.

Q34. What are radioactive wastes?

Ans:
Radioactive wastes are by-products of nuclear reactions and medical procedures.

Q35. Why are radioactive wastes dangerous?

Ans:
They cause genetic mutations, cancer, and long-term environmental damage.

Q36. How are radioactive wastes managed?

Ans:
By containment and deep geological burial.

Q37. Explain greenhouse effect.

Ans:
Greenhouse effect is trapping of heat by gases like CO₂, maintaining Earth’s temperature.

Q38. What is global warming?

Ans:
Global warming is the gradual increase in Earth’s average temperature due to enhanced greenhouse effect.

Q39. Mention two effects of global warming.

Ans:
Melting of glaciers and rise in sea level.

Q40. What are greenhouse gases? Name two.

Ans:
Gases that trap heat in atmosphere; carbon dioxide and methane.

Q41. How can global warming be controlled?

Ans:
By reducing fossil fuel use and promoting renewable energy.

Q42. What is ozone depletion?

Ans:
Reduction in ozone layer thickness due to CFCs.

Q43. Name one harmful effect of ozone depletion.

Ans:
Increased skin cancer due to UV radiation.

Q44. What is deforestation?

Ans:
Large-scale removal of forest cover.

Q45. List two causes of deforestation.

Ans:
Agricultural expansion and urbanization.

Q46. How does deforestation affect climate?

Ans:
It increases CO₂ levels, causing global warming.

Q47. What is afforestation?

Ans:
Planting trees in non-forested areas.

Q48. Why are forests important?

Ans:
They regulate climate, conserve biodiversity, and prevent soil erosion.

Q49. How do environmental issues affect biodiversity?

Ans:
Pollution and climate change destroy habitats and cause species extinction.

Q50. Why is environmental conservation important?

Ans:
It ensures ecological balance, human health, and sustainable development.

CBSE Board Exam Note

These Short Answer Questions (2–3 marks) are ideal for CBSE Class 12 board examinations, ensuring concept clarity, structured responses, and strict NCERT alignment.