Class 12 Biology Chapter 15 Biodiversity and Conservation Notes
15.1 Biodiversity
Biodiversity refers to the variety and variability of living organisms found on Earth at different levels of biological organisation.
Components of Biodiversity
There are three major components:
Genetic diversity
Variation of genes within a species
Example: Different varieties of rice, wheat
Species diversity
Variety of species within a region
Example: High species richness in tropical forests
Ecological diversity
Variety of ecosystems and habitats
Example: Forests, grasslands, deserts, wetlands
Estimation of Global Species Diversity
Ecologists estimate the total number of species by:
Studying species richness in well-explored regions
Comparing diversity across tropical, temperate and polar regions
Using measures such as:
Species density (species per unit area)
Species abundance
Proportional abundance indices
👉 These comparisons help extrapolate the global species count.
Why Do Tropics Show Maximum Species Richness?
Three major hypotheses explain this pattern:
Climatic stability
Tropics had fewer glaciations
Species evolved without frequent disturbances
Favourable environment
Warm temperature and high humidity
Supports growth and survival of diverse species
Higher solar energy
Leads to higher productivity
Can support more species at different trophic levels
Species–Area Relationship
Species richness increases with area explored
Represented by a regression slope (Z)
Significance of Slope (Z):
Small areas (country/region) → Z = 0.1–0.2
Large areas (continent) → Z = 0.6–1.2
👉 A higher slope indicates faster increase in species richness with area.
Causes of Species Loss (Biodiversity Loss)
Major causes include:
Habitat destruction and fragmentation
Forest fires, droughts and famines
Over-exploitation of resources
Pollution and intensive agriculture
Human population pressure
Importance of Biodiversity for Ecosystem Functioning
Biodiversity is crucial because it:
Increases ecosystem productivity
Improves recycling of nutrients and energy
Provides alternative pathways for survival
Maintains ecosystem stability
Prevents collapse if one species is lost (functional redundancy)
15.2 Biodiversity Conservation
Conservation is the protection, preservation and management of biodiversity.
Sacred Groves
Sacred Groves
Patches of forest protected due to religious or cultural beliefs
Found in:
Western Ghats
Rajasthan (Aravalli)
Madhya Pradesh
Meghalaya
Kerala
Sikkim
Role in Conservation:
Least disturbed forest patches
Protect endemic and rare species
Act as in-situ conservation sites
Maintain natural flora and fauna
Ecosystem Services: Control of Floods and Soil Erosion
Plants and biotic components help by:
Roots binding soil particles
Preventing topsoil erosion by wind and water
Increasing soil porosity
Enhancing water infiltration
Reducing surface runoff and floods
Why Is Animal Diversity Higher Than Plant Diversity?
Animals have:
Better dispersal ability
Nervous system and sensory organs
Faster adaptive responses
They survive and diversify better under changing conditions
Hence, animals show greater species diversification than plants
Deliberate Extinction: Is It Ever Justified?
Yes, in rare cases:
Example: Disease-causing organisms (e.g., poliovirus)
Justification:
Harmful to humans
Not essential producers or decomposers
Their removal does not disturb ecosystem balance
15.3 Summary (Exam Ready ✨)
Biodiversity has genetic, species and ecosystem levels
Tropics are biodiversity-rich due to stable climate and high productivity
Species–area relationship explains distribution of species
Biodiversity loss is mainly human-induced
Conservation is essential for ecosystem stability
Sacred groves are natural conservation sites
Ecosystem services protect soil, water and climate
✍️ Top 10 Short Question–Answers
Q1. What is biodiversity?
Answer: Biodiversity is the variety and variability of living organisms at different levels of biological organisation.
Q2. Name the three components of biodiversity.
Answer: Genetic diversity, species diversity and ecological diversity.
Q3. What is genetic diversity?
Answer: Variation of genes within a species.
Q4. What is species diversity?
Answer: Variety of species present in a particular region.
Q5. What is ecological diversity?
Answer: Variety of ecosystems and habitats in a region.
Q6. Why do tropics show maximum species richness?
Answer: Due to climatic stability, favourable environment and higher solar energy.
Q7. What is species–area relationship?
Answer: Species richness increases with increase in area explored.
Q8. Name any one major cause of biodiversity loss.
Answer: Habitat destruction and fragmentation.
Q9. What are sacred groves?
Answer: Forest patches protected due to religious or cultural beliefs.
Q10. Why is biodiversity important for ecosystem stability?
Answer: It maintains productivity and provides functional redundancy.
📝 Long Answer Questions
Q1. Explain the different components of biodiversity.
Answer:
Biodiversity has three major components:
1. Genetic diversity
Variation of genes within a species
Example: Different varieties of rice and wheat
2. Species diversity
Variety of species in a region
Example: High species richness in tropical forests
3. Ecological diversity
Variety of ecosystems and habitats
Example: Forests, grasslands, deserts and wetlands
Q2. Why do tropical regions show greater biodiversity than temperate regions?
Answer:
Tropics show maximum species richness due to:
Climatic stability: Fewer glaciations, less disturbance
Favourable environment: Warm temperature and high humidity
Higher solar energy: High productivity supports more species
These factors allow continuous evolution and survival of diverse species.
Q3. Describe causes and importance of biodiversity.
Answer:
Causes of biodiversity loss:
Habitat destruction and fragmentation
Over-exploitation of resources
Pollution and intensive agriculture
Human population pressure
Importance of biodiversity:
Increases ecosystem productivity
Improves nutrient and energy recycling
Maintains ecosystem stability
Prevents ecosystem collapse
📝 PYQs (Previous Year Questions)
🔹 1️⃣ Very Short Answer Questions (1 Mark)
What is biodiversity?
Name the three levels of biodiversity.
What is genetic diversity?
What is species diversity?
Why do tropical regions show high biodiversity?
What is species–area relationship?
Name one major cause of biodiversity loss.
What are sacred groves?
Name one ecosystem service provided by biodiversity.
What is meant by conservation of biodiversity?
🔹 2️⃣ Short Answer Questions (2–3 Marks)
Explain genetic, species and ecological diversity.
Why is biodiversity higher in tropics than in temperate regions?
What is species–area relationship? Mention the significance of slope (Z).
List any four causes of biodiversity loss.
Explain the importance of biodiversity for ecosystem functioning.
What are sacred groves? Write their role in conservation.
Why is animal diversity greater than plant diversity?
Explain how plants help in controlling floods and soil erosion.
What is meant by ecosystem stability?
Can deliberate extinction be justified? Explain with example.
🔹 3️⃣ Long Answer Questions (3–5 Marks)
Describe biodiversity and explain its different components.
Explain causes of biodiversity loss and its consequences.
Why is conservation of biodiversity necessary? Explain.
Describe sacred groves and their importance in biodiversity conservation.
Explain species–area relationship with suitable examples.
Discuss the role of biodiversity in ecosystem functioning.
🔹 4️⃣ Difference-Based PYQs (Very Important)
Genetic diversity vs Species diversity
Species diversity vs Ecological diversity
In-situ conservation vs Ex-situ conservation
Tropical biodiversity vs Temperate biodiversity
Habitat destruction vs Habitat fragmentation
🔹 5️⃣ Assertion–Reason / Concept-Based PYQs
Biodiversity loss is mainly human-induced. Justify.
Tropics are rich in biodiversity. Explain.
Sacred groves help in conservation of biodiversity. Justify.
Biodiversity provides functional redundancy in ecosystems. Explain.
Conservation of biodiversity is essential for human survival. Explain.
🔹 6️⃣ Diagram / Graph-Based PYQs
Graph showing species–area relationship.
Diagram showing levels of biodiversity.
Diagrammatic representation of causes of biodiversity loss.
❓FAQs (5)
FAQ 1. Why is animal diversity higher than plant diversity?
Animals have better dispersal ability and faster adaptive responses.
FAQ 2. What does slope (Z) represent in species–area relationship?
It shows the rate of increase in species richness with area.
FAQ 3. Why are sacred groves important in conservation?
They protect rare and endemic species as in-situ conservation sites.
FAQ 4. Can deliberate extinction ever be justified?
Yes, in rare cases like eradication of disease-causing organisms.
FAQ 5. How does biodiversity help in ecosystem functioning?
It ensures stability, productivity and alternative survival pathways.
| Chapter No. | Chapter Name | Visit |
|---|---|---|
| 1 | Reproduction in Organisms | Visit |
| 2 | Sexual Reproduction in Flowering Plants | Visit |
| 3 | Human Reproduction | Visit |
| 4 | Reproductive Health | Visit |
| 5 | Principles of Inheritance and Variation | Visit |
| 6 | Molecular Basis of Inheritance | Visit |
| 7 | Evolution | Visit |
| 8 | Human Health and Disease | Visit |
| 9 | Strategies for Enhancement in Food Production | Visit |
| 10 | Microbes in Human Welfare | Visit |
| 11 | Biotechnology: Principles and Processes | Visit |
| 12 | Biotechnology and its Applications | Visit |
| 13 | Organisms and Populations | Visit |
| 14 | Ecosystem | Visit |
| 15 | Biodiversity and Conservation | Visit |
| 16 | Environmental Issues | Visit |
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