Chapter 16: Environmental Issues Class 12 Biology NCERT Solutions

Study pollution types, global warming, and environmental management with Chapter 16 NCERT Solutions. Download free PDFs and prepare systematically. Scroll below to find detailed exercise answers.

What You Will Learn in Chapter 15 – Biodiversity and Conservation

This chapter introduces students to the richness of life on Earth, covering different types of biodiversity and conservation strategies. It also includes national and global efforts to prevent biodiversity loss.

Key Topics Covered:

1. Biodiversity: Definition and Types

  • Biodiversity refers to the variety of life forms found on Earth.

  • Three levels of biodiversity:

    • Genetic diversity: Variety of genes within species.

    • Species diversity: Variety of species in a given region.

    • Ecological diversity: Variety of ecosystems like forests, deserts, wetlands, etc.

2. Biodiversity in India

  • India is one of the 12 mega-diverse countries in the world.

  • Hotspots of biodiversity in India: Western Ghats, Himalayas, Indo-Burma, and Sundaland.

  • High species richness and endemism in India.

3. Patterns of Biodiversity

  • Latitudinal gradient: Biodiversity increases from the poles to the equator.

  • Species-area relationship: Greater the area, higher the number of species.

  • Described by Alexander von Humboldt through a mathematical model.

4. Importance of Biodiversity

  • Ecological role: Maintains ecosystem functions and stability.

  • Economic value: Provides food, fuel, fiber, medicine, and ecosystem services.

  • Ethical and aesthetic values: Respect for all forms of life; inspiration, culture, and heritage.

5. Loss of Biodiversity

  • Major causes of biodiversity loss (HIPPO):

    • H: Habitat loss and fragmentation.

    • I: Invasive species.

    • P: Pollution.

    • P: Population explosion (human).

    • O: Overexploitation of resources.

  • Extinction of species and ecosystem imbalance.

6. Biodiversity Conservation

  • In Situ Conservation:

    • Protecting species in their natural habitat.

    • Includes biosphere reserves, national parks, wildlife sanctuaries, and sacred groves.

  • Ex Situ Conservation:

    • Protecting species outside their natural habitat.

    • Includes zoos, botanical gardens, seed banks, cryopreservation.

7. Global Efforts for Conservation

  • IUCN Red List: Categorizes species based on extinction risk.

  • Convention on Biological Diversity (CBD): International treaty to conserve and share genetic resources.

  • Earth Summit (1992), Rio de Janeiro: Promoted sustainable development and conservation.

Why Use Our NCERT Solutions for Chapter 15?

Our detailed and student-friendly solutions for Chapter 15: Biodiversity and Conservation help simplify complex environmental concepts and enhance understanding with diagrams and real-world examples. These solutions are designed for effective exam preparation and concept clarity.

Highlights of Our Solutions:

  • All NCERT Intext and Exercise questions answered in a simple, precise manner.

  • Definitions, examples, and significance of different levels of biodiversity.

  • Diagrams to explain species-area relationships and conservation models.

  • Practical examples of biodiversity conservation in India and globally.

  • Perfect for CBSE Board, NEET, and other entrance exam preparation.

NCERT Solutions for Chapter 15 – Biodiversity and Conservation

Intext Questions:

  • Detailed explanations of the three levels of biodiversity.

  • Examples and significance of Indian biodiversity hotspots.

  • Real-life applications of conservation strategies.

Exercise Questions (Q.1 to Q.10):

  • Answers to conceptual questions on biodiversity loss and its consequences.

  • Explanation of in situ vs ex situ conservation methods.

  • Discussion on the value of biodiversity—ecological, economic, and ethical.

  • Graph-based questions on species-area relationships.

Download Chapter 15 Solutions PDF – Biodiversity and Conservation

Access a free, downloadable PDF with complete NCERT solutions and diagrams to aid revision and exam success.

What’s Included:

  • Well-structured, easy-to-read solutions.

  • Visual aids for better concept retention.

  • Quick reference glossary of important terms.

Recommended Preparation Tips:

  • Focus on HIPPO – the five major causes of biodiversity loss.

  • Memorize the difference between in situ and ex situ conservation with examples.

  • Study biodiversity hotspots in India and their significance.

  • Understand the species-area relationship and be able to interpret related graphs.

  • Be aware of international treaties like the CBD and the purpose of the IUCN Red List.

Additional Study Resources:

  • Chapter 15 Biology Notes – Biodiversity and Conservation.

  • NCERT Exemplar Problems and Solutions.

  • NEET-level MCQs and assertion-reason questions.

  • Flashcards for biodiversity terms and conservation types.

  • Quick-revision infographic on conservation strategies.

Understanding the Value of Biodiversity

Chapter 15 emphasizes the importance of preserving biodiversity not only for ecological balance but also for the well-being of current and future generations. By studying this chapter, students become more aware of their role as responsible citizens of the planet and the need to protect Earth’s rich biological heritage.

Master this chapter to contribute meaningfully toward a sustainable and biodiverse future.

NCERT Solutions for Class 12 Biology Chapter 16 – Environmental Issues

Question 1. What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.

Answer: Domestic sewage contains:

  • Suspended solids: Soil, sand, and silt particles.
  • Colloidal particles: Organic/inorganic matter like faeces, cloth, paper.
  • Dissolved solids: Nutrients such as nitrates, phosphates, ammonia, calcium, sodium.
  • Pathogens: Disease-causing microbes (bacteria, viruses).
Effects on rivers:
  • Algal blooms due to nutrient enrichment (eutrophication).
  • Oxygen depletion due to increased BOD (Biological Oxygen Demand).
  • Death of aquatic organisms.
  • Spread of waterborne diseases.
  • Bad odour and water pollution.

Question 2. List all the wastes that you generate at home, school or during your trips to other places. Could you very easily reduce the generation of these wastes? Which would be difficult or rather impossible to reduce?

Answer:

  • Home: Plastic bags, food waste, paper, bottles.
  • School: Stationery waste, chalk dust, paper.
  • Trips: Disposable containers, packaging materials, tissues.
Easily reducible wastes: Plastic bags, disposable usage.
Difficult to reduce: Organic kitchen waste, essential packaging materials.

Question 3. Discuss the causes and effects of global warming. What measures need to be taken to control global warming?

Answer: Causes:

  • Increase in greenhouse gases (CO₂, CH₄, N₂O, CFCs).
  • Fossil fuel burning, deforestation, and industrial emissions.
Effects:
  • Rising Earth’s temperature.
  • Melting glaciers and rising sea levels.
  • Extreme weather events.
  • Loss of biodiversity and crop failures.
Control measures:
  • Promote renewable energy sources.
  • Reforestation and afforestation.
  • Reduce the use of fossil fuels.
  • Use energy-efficient appliances and promote public transport.

Question 4. Match the items given in Column A with those in Column B.

Answer:

Column AColumn B
Catalytic converterReduces vehicular emission
EutrophicationNutrient enrichment
Particulate matterRespiratory problems
Snow blindnessUV-B exposure

Question 5. Write critical notes on the following:

(a) Eutrophication: Nutrient enrichment in water bodies leading to algal blooms, oxygen depletion, and death of aquatic life.
(b) Biological magnification: The increase in concentration of non-biodegradable pollutants like DDT in successive trophic levels of the food chain.
(c) Groundwater depletion and ways for its replenishment: Excess withdrawal of groundwater leads to depletion. Replenishment methods include rainwater harvesting, afforestation, constructing recharge pits, and efficient water use.

Question 6. Why ozone hole forms over Antarctica? How will enhanced ultraviolet radiation affect us?

Answer: Ozone hole formation:

  • Cold temperatures form polar stratospheric clouds.
  • CFCs release chlorine radicals which break down ozone.
  • Sunlight after polar winter triggers rapid ozone depletion.
Effects of UV-B radiation:
  • Causes skin cancer and cataracts.
  • Damages DNA in living organisms.
  • Affects plankton and aquatic ecosystems.

Question 7. Discuss the role of women and communities in protection and conservation of forests.

Answer:

  • Bishnoi Movement: Led by Amrita Devi, villagers protected trees by sacrificing their lives.
  • Chipko Movement: Villagers, especially women, hugged trees to prevent their felling.
These movements show how women and local communities play a vital role in conserving forests and biodiversity.

Question 8. What measures, as an individual, would you take to reduce environmental pollution?

Answer:

  • Avoid plastic and use reusable items.
  • Segregate waste into biodegradable and non-biodegradable.
  • Use public transport, carpool, or cycle.
  • Plant trees and save water and electricity.
  • Avoid burning waste and use eco-friendly products.

Question 9. Discuss briefly the following:

(a) Radioactive wastes: Waste produced by nuclear power plants; hazardous and requires long-term safe disposal.
(b) Defunct ships and e-wastes: Old ships and electronic waste contain heavy metals and toxic substances, leading to pollution when not handled properly.
(c) Municipal solid wastes: Household and commercial waste, including plastics, kitchen waste, paper, etc., requiring proper segregation, recycling, and disposal.

Question 10. What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?

Answer: Measures taken:

  • Introduction of CNG buses and auto-rickshaws.
  • Phasing out of old vehicles.
  • Implementation of Euro-II emission norms.
  • Use of unleaded petrol and catalytic converters.
Result: A significant decrease in SO₂ and particulate matter levels. Air quality has improved but ongoing efforts are necessary.

Question 11. Discuss briefly the following:

(a) Greenhouse gases: Gases such as CO₂, CH₄, and N₂O that trap heat in the atmosphere, causing global warming.
(b) Catalytic converter: A device installed in vehicles to reduce toxic gases by converting them into less harmful substances like CO₂ and N₂.
(c) Ultraviolet B (UV-B): Harmful radiation from the sun; overexposure can cause skin cancer, cataracts, and damage to living organisms.