CBSE Class 12 Biology Case-Based Questions – Environmental Issues (NCERT Based)

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

CBSE Class 12 Biology Chapter 16 Case-Based 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 (Competency-Based / Case-Based Questions)

Case-Based Questions with Answers

(Prepared strictly according to NCERT concepts and the latest CBSE competency-based assessment pattern)

Section A: Air Pollution and Its Control (Case 1–6)

Case 1

A city records increased cases of asthma and reduced visibility during winter months due to vehicular emissions.

Q1. Identify the major environmental issue involved.
Ans: Air pollution.

Q2. Name the type of smog commonly formed in such cities.
Ans: Photochemical smog.

Case 2

Industries release smoke containing fine particles into the atmosphere.

Q1. Which air pollutant is mainly responsible here?
Ans: Particulate matter.

Q2. Name one industrial device used to control such pollution.
Ans: Electrostatic precipitator.

Case 3

Automobiles are fitted with special devices to reduce toxic exhaust gases.

Q1. Name the device used.
Ans: Catalytic converter.

Q2. Which harmful gas is converted into carbon dioxide by this device?
Ans: Carbon monoxide.

Case 4

Marble monuments near industrial zones show surface corrosion.

Q1. Which environmental phenomenon causes this damage?
Ans: Acid rain.

Q2. Name one gas responsible for acid rain formation.
Ans: Sulphur dioxide.

Case 5

Use of cleaner fuels is promoted in urban areas.

Q1. Name one such fuel recommended by NCERT.
Ans: Compressed Natural Gas (CNG).

Q2. How does it help the environment?
Ans: It produces fewer harmful emissions.

Case 6

Pollution control laws enforce emission standards.

Q1. Why are such standards important?
Ans: They reduce health hazards and environmental damage.

Q2. Which authority enforces these standards in India?
Ans: Pollution Control Boards.

Section B: Water Pollution and Its Control (Case 7–12)

Case 7

A river receiving untreated sewage shows excessive algal growth.

Q1. Name the process responsible for algal bloom.
Ans: Eutrophication.

Q2. How does this affect aquatic life?
Ans: It depletes dissolved oxygen causing fish death.

Case 8

Industrial effluents containing heavy metals are discharged into water bodies.

Q1. What type of pollution is this?
Ans: Water pollution.

Q2. Name one harmful effect of heavy metals.
Ans: Bioaccumulation and toxicity.

Case 9

Villagers suffer from cholera due to contaminated water.

Q1. What type of disease is cholera?
Ans: Water-borne disease.

Q2. Name one preventive measure.
Ans: Proper sewage treatment.

Case 10

Farm runoff carries fertilizers into lakes.

Q1. Which nutrients cause water pollution here?
Ans: Nitrates and phosphates.

Q2. What practice can reduce this problem?
Ans: Controlled use of fertilizers.

Case 11

Microorganisms are used in sewage treatment plants.

Q1. Why are microbes important in treatment?
Ans: They decompose organic waste.

Q2. What does this reduce in water?
Ans: Pollution load.

Case 12

Oil spills occur in marine ecosystems.

Q1. How do oil spills affect aquatic organisms?
Ans: They block oxygen exchange and poison organisms.

Q2. Name one long-term effect.
Ans: Disruption of food chains.

Section C: Solid Waste Management (Case 13–17)

Case 13

Urban areas generate large amounts of garbage daily.

Q1. What type of waste is this?
Ans: Municipal solid waste.

Q2. Name one proper disposal method.
Ans: Sanitary landfill.

Case 14

Organic kitchen waste is converted into manure.

Q1. Identify this process.
Ans: Composting.

Q2. Why is it eco-friendly?
Ans: It recycles nutrients naturally.

Case 15

Plastics and metals are reused after processing.

Q1. What waste management method is used?
Ans: Recycling.

Q2. Name one benefit of recycling.
Ans: Conservation of resources.

Case 16

Burning waste releases toxic gases.

Q1. What method is being used?
Ans: Incineration.

Q2. Mention one disadvantage.
Ans: Air pollution.

Case 17

Discarded electronic devices accumulate in landfills.

Q1. What type of waste is this?
Ans: Electronic waste (e-waste).

Q2. Why is e-waste hazardous?
Ans: It contains toxic metals.

Section D: Agrochemicals and Radioactive Wastes (Case 18–21)

Case 18

Excessive pesticide use affects birds of prey.

Q1. Name the phenomenon responsible.
Ans: Biomagnification.

Q2. Which chemical is commonly cited in NCERT?
Ans: DDT.

Case 19

Soil fertility declines after prolonged chemical fertilizer use.

Q1. Which agents are responsible?
Ans: Agrochemicals.

Q2. Suggest one sustainable alternative.
Ans: Organic farming.

Case 20

Nuclear power plants generate hazardous waste.

Q1. What type of waste is produced?
Ans: Radioactive waste.

Q2. Name one health hazard caused.
Ans: Cancer.

Case 21

Radioactive waste is stored deep underground.

Q1. What method is used here?
Ans: Deep geological burial.

Q2. Why is this necessary?
Ans: To prevent radiation leakage.

Section E: Climate Change, Ozone Depletion and Deforestation (Case 22–25)

Case 22

Global temperatures rise due to increased CO₂ emissions.

Q1. Name the phenomenon responsible.
Ans: Global warming.

Q2. What causes this rise in temperature?
Ans: Enhanced greenhouse effect.

Case 23

Increased UV radiation affects human health.

Q1. Which environmental problem causes this?
Ans: Ozone depletion.

Q2. Name one chemical responsible.
Ans: Chlorofluorocarbons (CFCs).

Case 24

Large forest areas are cleared for agriculture.

Q1. Identify the environmental issue.
Ans: Deforestation.

Q2. Name one ecological consequence.
Ans: Loss of biodiversity.

Case 25

Communities plant trees to restore forest cover.

Q1. What is this practice called?
Ans: Afforestation.

Q2. How does it help the environment?
Ans: It reduces CO₂ and restores ecosystems.

CBSE Board Exam Note

These case-based questions are designed to develop analytical thinking, application of concepts, and competency-based learning, strictly aligned with NCERT Chapter 16 – Environmental Issues and the CBSE Class 12 board examination pattern.