CBSE Class 12 Biology Long Answer Questions – Biodiversity and Conservation (NCERT Based)

Unit V: Ecology and Environment | Chapter 15: Biodiversity and Conservation

CBSE Class 12 Biology Chapter 15 Long Answer Questions – Biodiversity and Conservation (NCERT)

Course & Examination Details

• Course: CBSE Class 12 Biology
• Unit: Unit V – Ecology and Environment
• Chapter: Chapter 15 – Biodiversity and Conservation
• Board: Central Board of Secondary Education (CBSE)
• Syllabus Base: Strictly as per NCERT Textbook
• Exam Relevance: CBSE Class 12 Board Examinations (5-mark questions)

Long Answer Type Questions (120–150 Words Each)

(Prepared strictly according to NCERT syllabus, using standard CBSE answer-writing format)

Section A: Biodiversity and Its Levels (Q1–Q6)

Q1. Define biodiversity and explain its three levels.

Ans:
Biodiversity refers to the total variety of life forms present on Earth, including plants, animals, and microorganisms. It is studied at three levels. Genetic diversity refers to variation in genes within a species, enabling adaptation to environmental changes. Species diversity includes the variety and relative abundance of species in a given area, contributing to ecosystem stability. Ecosystem diversity refers to the variety of ecosystems such as forests, grasslands, deserts, wetlands, and marine ecosystems present in a region. Each level of biodiversity plays a crucial role in maintaining ecological balance, ensuring ecosystem resilience, and supporting life processes. Loss at any level can adversely affect ecosystem functioning and sustainability.

Q2. Explain genetic diversity and its importance with suitable examples.

Ans:
Genetic diversity refers to variation in genes within individuals of the same species. This diversity allows populations to adapt to changing environmental conditions, resist diseases, and survive adverse situations. For example, different varieties of rice grown in India show genetic diversity, enabling resistance to pests, drought, or floods. High genetic diversity increases the chances of survival during environmental stress, while low genetic diversity makes species vulnerable to extinction. Thus, genetic diversity is essential for evolution, long-term survival of species, and stability of ecosystems.

Q3. Describe species diversity and its significance.

Ans:
Species diversity refers to the variety and relative abundance of different species present in a particular region. It includes species richness (number of species) and species evenness (distribution of individuals among species). High species diversity increases ecosystem stability, productivity, and resilience against disturbances. Tropical rainforests exhibit high species diversity due to stable climate and high productivity. Ecosystems with greater species diversity are better able to withstand environmental changes and recover from disturbances, ensuring long-term sustainability.

Q4. What is ecosystem diversity? Explain its importance.

Ans:
Ecosystem diversity refers to the variety of ecosystems present within a geographical area, such as forests, grasslands, wetlands, deserts, and marine ecosystems. Each ecosystem supports unique communities of organisms and ecological processes. Ecosystem diversity ensures availability of diverse habitats, enhances overall biodiversity, and supports ecological services like nutrient cycling, climate regulation, and water purification. Loss of ecosystem diversity can lead to habitat destruction and species extinction, ultimately disturbing ecological balance.

Q5. Why is India considered a mega-diverse country?

Ans:
India is considered a mega-diverse country because it harbors nearly 8% of global species diversity while occupying only about 2.4% of the world’s land area. This rich biodiversity is due to India’s diverse climatic conditions, varied geography, and wide range of ecosystems such as forests, grasslands, deserts, wetlands, and marine habitats. India also has high endemism, especially in regions like the Western Ghats and the Eastern Himalayas.

Q6. Explain endemism and its ecological significance.

Ans:
Endemism refers to species that are restricted to a specific geographical area and are not found elsewhere. Endemic species contribute significantly to regional biodiversity and ecological uniqueness. However, due to their limited distribution, they are highly vulnerable to habitat loss and environmental changes. Conservation of endemic species is crucial because their extinction would result in irreversible loss of biodiversity.

Section B: Patterns of Biodiversity (Q7–Q11)

Q7. Explain the latitudinal gradient in biodiversity.

Ans:
Latitudinal gradient refers to the pattern of increasing biodiversity from the poles towards the equator. Tropical regions show the highest biodiversity, while polar regions have the lowest. This pattern is attributed to stable climatic conditions, high productivity, longer evolutionary time, and minimal seasonal variations in the tropics. These conditions promote speciation and reduce extinction rates, leading to higher biodiversity.

Q8. Describe the species–area relationship.

Ans:
The species–area relationship states that species richness increases with increasing area. It is represented by the equation S = CAᶻ, where S is species richness, A is area, and C and Z are constants. This relationship is often plotted on a logarithmic scale. Larger areas provide more habitats and resources, supporting greater species diversity. The slope (Z value) is steeper for larger regions like continents.

Q9. What are biodiversity hotspots? Explain their importance.

Ans:
Biodiversity hotspots are regions with high species richness, high endemism, and significant threat of habitat loss. These areas cover a small fraction of Earth’s land but support a large proportion of global biodiversity. Conservation of hotspots is crucial because protecting these regions ensures maximum biodiversity conservation within limited areas. The Western Ghats is an important biodiversity hotspot in India.

Q10. Explain why biodiversity is unevenly distributed on Earth.

Ans:
Biodiversity is unevenly distributed due to variations in climate, geography, resource availability, and evolutionary history. Tropical regions support higher biodiversity due to favorable conditions, while extreme environments like deserts and polar regions support fewer species.

Q11. Why do islands show unique biodiversity patterns?

Ans:
Islands are geographically isolated, leading to speciation and high endemism. However, limited area and resources also increase extinction risk, making island biodiversity unique and fragile.

Section C: Importance of Biodiversity (Q12–Q16)

Q12. Explain the ecological importance of biodiversity.

Ans:
Biodiversity maintains ecosystem stability, productivity, and resilience. Diverse ecosystems efficiently recycle nutrients, regulate climate, support pollination, and maintain food webs. Higher biodiversity enhances resistance to environmental disturbances and ensures continuity of ecosystem services essential for life.

Q13. Describe the economic importance of biodiversity.

Ans:
Biodiversity provides essential resources such as food, medicines, timber, fuel, fibers, and genetic materials. Many modern medicines are derived from plants and microorganisms. Biodiversity also supports agriculture, fisheries, forestry, and ecotourism, contributing significantly to economic development.

Q14. Explain the aesthetic and cultural value of biodiversity.

Ans:
Biodiversity provides recreational, spiritual, and aesthetic benefits. Natural landscapes, wildlife, and forests enhance mental well-being and cultural identity. Many traditions and religious beliefs are closely associated with biodiversity.

Q15. Why is biodiversity ethically important?

Ans:
Every species has intrinsic value and the right to exist, independent of human use. Humans have a moral responsibility to conserve biodiversity for future generations and maintain ecological balance.

Q16. How does biodiversity contribute to ecosystem resilience?

Ans:
High biodiversity provides functional redundancy, allowing ecosystems to recover quickly from disturbances such as natural disasters or climate change.

Section D: Loss of Biodiversity (Q17–Q21)

Q17. Explain the major causes of biodiversity loss.

Ans:
The major causes of biodiversity loss, known as the Evil Quartet, include habitat loss and fragmentation, over-exploitation, alien species invasion, and co-extinctions. Habitat destruction is the primary cause, while overuse of resources and invasive species further accelerate species extinction.

Q18. Describe habitat loss and fragmentation as a cause of extinction.

Ans:
Habitat loss due to deforestation, agriculture, and urbanization destroys natural living spaces. Fragmentation breaks habitats into smaller patches, isolating populations and reducing genetic diversity, leading to extinction.

Q19. Explain over-exploitation and its consequences.

Ans:
Over-exploitation refers to excessive use of biological resources beyond sustainable limits. Examples include overfishing and hunting, leading to population decline and extinction of species.

Q20. What are alien species invasions? Give examples.

Ans:
Alien species invasions occur when non-native species enter an ecosystem and outcompete native species. Examples include Lantana camara in India. These invasions disrupt ecosystems and reduce native biodiversity.

Q21. Explain co-extinctions with suitable examples.

Ans:
Co-extinctions occur when extinction of one species leads to extinction of dependent species, such as parasites or pollinators associated with a specific host.

Section E: Biodiversity Conservation (Q22–Q25)

Q22. Explain biodiversity conservation and its objectives.

Ans:
Biodiversity conservation involves protection, sustainable use, and restoration of biological resources. Its objectives include preventing species extinction, maintaining ecosystem balance, and ensuring sustainable development.

Q23. Describe in situ conservation with examples.

Ans:
In situ conservation protects species in their natural habitats through national parks, wildlife sanctuaries, and biosphere reserves. It conserves entire ecosystems and allows natural evolution to continue.

Q24. Explain ex situ conservation with examples.

Ans:
Ex situ conservation involves protecting species outside their natural habitats, such as in zoos, botanical gardens, seed banks, and gene banks. It is useful for critically endangered species.

Q25. Why is conservation of biodiversity essential for future generations?

Ans:
Conservation ensures ecological balance, sustainable resource availability, climate stability, and survival of life on Earth, benefiting future generations.

CBSE Board Exam Tip

These long answer questions (5 marks) are ideal for CBSE board examinations, emphasizing definitions, explanations, examples, and structured presentation strictly aligned with NCERT Chapter 15 – Biodiversity and Conservation.