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Biodiversity and Conservation

NCERT Class 11 · Geography Based on NCERT Class 11 Geography textbook · Free CBSE study kit

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Chapter Notes

Overview
This chapter explains the concept of biodiversity, its levels, importance, and the urgent need for its conservation. It exists in the syllabus to make students understand that biodiversity is the result of billions of years of evolution and is essential for ecological balance, human survival, and sustainable development. The one big idea a student must walk away with is that biodiversity is our living wealth, and its loss due to human activities threatens the stability of ecosystems and our own existence.
Key Concepts (14)
Biodiversity
Biodiversity is the number and variety of organisms found within a specified geographic region. It refers to the varieties of plants, animals and micro-organisms, the genes they contain and the ecosystems they form.
e.g. The variety of life forms found in a tropical rainforest, including thousands of tree species, insects, birds, and mammals, is an example of biodiversity.
Genetic Diversity
Genetic biodiversity refers to the variation of genes within species.
e.g. Humans belong to the species Homo sapiens but differ in height, colour, and physical appearance due to genetic diversity.
Species Diversity
This refers to the variety of species. It relates to the number of species in a defined area. The diversity of species can be measured through its richness, abundance and types.
e.g. A coral reef has high species diversity with many fish, corals, and invertebrates, while a desert has low species diversity.
Ecosystem Diversity
The broad differences between ecosystem types and the diversity of habitats and ecological processes occurring within each ecosystem type constitute the ecosystem diversity.
e.g. The grasslands and sholas in Indira Gandhi National Park, Annamalai, Western Ghats are an example of ecosystem diversity.
Hotspots of Diversity
Areas rich in species diversity are called hotspots of diversity.
e.g. Madagascar, where about 85 per cent of the plants and animals are found nowhere else in the world, is a biodiversity hotspot.
Exotic Species
Species which are not the natural inhabitants of the local habitat but are introduced into the system are called exotic species.
e.g. The introduction of certain exotic plants or animals that damage the natural biotic community of an ecosystem.
Endangered Species
It includes those species which are in danger of extinction.
e.g. Red Panda is an endangered species.
Vulnerable Species
This includes the species which are likely to be in danger of extinction in near future if the factors threatening to their extinction continue.
e.g. Species whose population has reduced greatly and survival is not assured.
Rare Species
Population of these species is very small in the world; they are confined to limited areas or thinly scattered over a wider area.
e.g. Humboldtia decurrens Bedd — a highly rare endemic tree of Southern Western Ghats (India).
Mega Diversity Centres
Countries situated in the tropical region that possess a large number of the world’s species diversity are called mega diversity centres.
e.g. India, Brazil, Indonesia, and Australia are among the 12 mega diversity centres.
Red List of Threatened Species
The IUCN publishes information about endangered species world-wide as the Red List of threatened species.
e.g. The Red List includes species like the Red Panda and many others that are at risk of extinction.
Convention of Biodiversity
An international agreement signed by the Government of India along with 155 other nations at the Earth Summit held at Rio de Janeiro, Brazil in June 1992.
e.g. The convention aims to promote conservation and sustainable use of biodiversity.
Earth Summit
The United Nations Conference on Environment and Development held at Rio de Janeiro, Brazil in June 1992.
e.g. At the Earth Summit, the Convention of Biodiversity was signed by 156 nations including India.
Agro-biodiversity
Crop diversity, which is also called agro-biodiversity, is an important part of biodiversity.
e.g. Different varieties of rice, wheat, and millets grown in India represent agro-biodiversity.
How It Works
Formation of Biodiversity through Evolution
  1. Biodiversity is the result of 2.5-3.5 billion years of evolution.
  2. The basic cause for weathering variations and resultant biodiversity is the input of solar energy and water.
  3. Areas rich in solar energy and water (like tropical regions) have a wide spectrum of biodiversity.
  4. Before the advent of humans, Earth supported more biodiversity than in any other period.
💡 Students often forget that biodiversity is a result of evolution over billions of years, not a static phenomenon.
Classification of Threatened Species by IUCN
  1. The IUCN classifies threatened species into three categories: Endangered, Vulnerable, and Rare.
  2. Endangered species are those in danger of extinction.
  3. Vulnerable species are likely to become endangered if threatening factors continue.
  4. Rare species have very small populations, confined to limited areas.
💡 Students often confuse 'vulnerable' with 'endangered' — vulnerable is a less severe category than endangered.
Steps for Biodiversity Conservation (World Conservation Strategy)
  1. Efforts should be made to preserve the species that are endangered.
  2. Prevention of extinction requires proper planning and management.
  3. Varieties of food crops, forage plants, timber trees, livestock, animals and their wild relatives should be preserved.
  4. Each country should identify habitats of wild relatives and ensure their protection.
  5. Habitats where species feed, breed, rest and nurse their young should be safeguarded and protected.
  6. International trade in wild plants and animals be regulated.
💡 Students often miss the step about 'habitats where species feed, breed, rest and nurse their young' — this is a specific point asked in exams.
Identification of Biodiversity Hotspots
  1. The IUCN has identified certain areas as biodiversity hotspots.
  2. Hotspots are defined according to their vegetation.
  3. Plants are important because they determine the primary productivity of an ecosystem.
  4. Most hotspots rely on species-rich ecosystems for food, firewood, cropland, and income from timber.
💡 Students often think hotspots are defined by animal diversity, but the text clearly states they are defined according to vegetation.
Exam Traps — Don't Make These Mistakes
⚠ Confusing 'Endangered' with 'Vulnerable'
✗ Endangered species are those that are likely to become extinct in the near future.
→ The text defines 'endangered' as species in danger of extinction, while 'vulnerable' are those likely to become endangered if threats continue. The student has mixed the two definitions.
✓ Endangered species are those which are in danger of extinction. Vulnerable species are those which are likely to be in danger of extinction in near future if the factors threatening to their extinction continue.
⚠ Misstating the Number of Mega Diversity Centres
✗ There are 10 mega diversity centres in the world.
→ The text explicitly states there are 12 such countries. Students often guess or misremember the number.
✓ There are 12 mega diversity centres: Mexico, Columbia, Ecuador, Peru, Brazil, Democratic Republic of Congo, Madagascar, China, India, Malaysia, Indonesia and Australia.
⚠ Confusing 'Hotspots' with 'Mega Diversity Centres'
✗ Biodiversity hotspots and mega diversity centres are the same thing.
→ Hotspots are areas identified by IUCN based on vegetation and vulnerability, while mega diversity centres are countries in tropical regions with high species diversity. They are different concepts.
✓ Biodiversity hotspots are areas identified by IUCN according to their vegetation and vulnerability, while mega diversity centres are 12 tropical countries that possess a large number of the world’s species diversity.
⚠ Thinking Biodiversity is Only About Species
✗ Biodiversity means the number of different species in an area.
→ Biodiversity includes three levels: genetic diversity, species diversity, and ecosystem diversity. Reducing it to only species is incomplete.
✓ Biodiversity refers to the varieties of plants, animals and micro-organisms, the genes they contain and the ecosystems they form. It includes genetic, species, and ecosystem diversity.
⚠ Forgetting the Role of Solar Energy and Water
✗ Biodiversity is richer in tropical regions because of the warm climate.
→ The text specifically states that the basic cause for weathering variations and resultant biodiversity is the input of solar energy and water. 'Warm climate' is vague and misses the precise factors.
✓ The basic cause for biodiversity variations is the input of solar energy and water. Areas rich in these inputs, like tropical regions, have a wide spectrum of biodiversity.
Compare & Contrast
Threat level
Endangered Species
Vulnerable Species
Endangered species are in danger of extinction, while vulnerable species are likely to become endangered in the near future if threatening factors continue.
Definition and scope
Biodiversity Hotspots
Mega Diversity Centres
Biodiversity hotspots are areas identified by IUCN based on vegetation and vulnerability, while mega diversity centres are 12 tropical countries that possess a large number of the world’s species diversity.
Level of biodiversity
Genetic Diversity
Species Diversity
Genetic diversity refers to variation of genes within a species, while species diversity refers to the variety of species in a defined area.
Exam Focus
Marks pattern: This chapter typically appears in board exams as: 2-3 MCQs (1 mark each), 1 short answer question (3 marks), and 1 long answer question (5 marks). Total weightage: approximately 10-12 marks.
Most asked: Levels of biodiversity (genetic, species, ecosystem) · Importance of biodiversity (ecological, economic, scientific) · Causes of loss of biodiversity · Classification of threatened species (endangered, vulnerable, rare) · Biodiversity hotspots and mega diversity centres · Conservation measures (World Conservation Strategy steps, Wild Life Protection Act, 1972, Convention of Biodiversity)
Don't skip: Long answer question on the roles of biodiversity (ecological, economic, scientific) — 5 marks; Long answer question on factors responsible for loss of biodiversity and steps needed to prevent them — 5 marks; Short answer question on levels of biodiversity with examples — 3 marks
One-Line Revision (read aloud before the exam)
  1. Biodiversity is the number and variety of organisms found within a specified geographic region, including genes, species, and ecosystems.
  2. The three levels of biodiversity are genetic diversity, species diversity, and ecosystem diversity.
  3. Genetic diversity refers to the variation of genes within species, essential for healthy breeding.
  4. Species diversity relates to the number of species in a defined area, measured through richness, abundance, and types.
  5. Ecosystem diversity refers to the broad differences between ecosystem types and the diversity of habitats and ecological processes within each.
  6. Areas rich in species diversity are called hotspots of diversity.
  7. Biodiversity plays ecological, economic, and scientific roles in shaping nature.
  8. Ecologically, each species performs a function; more diverse ecosystems are more stable and productive.
  9. Economically, biodiversity provides food crops, livestock, forests, fish, and medicinal resources.
  10. Scientifically, each species gives clues about how life evolved and functions.
  11. Loss of biodiversity is caused by over-exploitation, deforestation, natural calamities, pollution, exotic species, and poaching.
  12. IUCN classifies threatened species into endangered, vulnerable, and rare categories.
  13. Endangered species are in danger of extinction; vulnerable species may become endangered soon; rare species have very small populations.
  14. The World Conservation Strategy suggests preserving endangered species, protecting habitats, and regulating international trade.
  15. The Government of India passed the Wild Life (Protection) Act, 1972 to establish national parks, sanctuaries, and biosphere reserves.
  16. There are 12 mega diversity centres including India, Brazil, and Indonesia.
  17. Biodiversity hotspots are defined according to their vegetation, which determines primary productivity.
  18. The Convention of Biodiversity was signed at the Earth Summit in Rio de Janeiro, Brazil in June 1992.
  19. Exotic species are non-native species that can damage natural biotic communities.
  20. The average half-life of a species is estimated at between one and four million years, and 99 per cent of species that ever lived are now extinct.

MCQs — 10 Questions with Answers

Q1. Biodiversity is defined as:

  • A. The number and variety of organisms found within a specified geographic region ✓
  • B. Only the different species of plants in a forest
  • C. The total population of animals in an ecosystem
  • D. The number of endangered species in the world

Answer: A — Biodiversity encompasses all organisms (plants, animals, micro-organisms), genes they contain, and ecosystems they form within a geographic region.

Q2. Which of the following is NOT a level of biodiversity?

  • A. Genetic diversity
  • B. Species diversity
  • C. Population diversity ✓
  • D. Ecosystem diversity

Answer: C — The three recognized levels are genetic, species, and ecosystem diversity; population diversity is not a formal level of biodiversity classification.

Q3. Genetic diversity within a species is essential for:

  • A. Healthy breeding and survival of the population ✓
  • B. Reducing the number of species
  • C. Preventing natural calamities
  • D. Increasing deforestation

Answer: A — Genetic diversity provides variation in traits within a species, ensuring healthy reproduction and ability to adapt to changing conditions.

Q4. Tropical forests occupy approximately what fraction of Earth's total land area but contain what percentage of world species?

  • A. One-half of land area; 25% of species
  • B. One-fourth of land area; 50% of species ✓
  • C. One-fourth of land area; 75% of species
  • D. One-third of land area; 50% of species

Answer: B — The study material explicitly states tropical regions occupy about one-fourth of total area but contain 50% of the world's species.

Q5. Which statement best explains why high biodiversity makes an ecosystem more stable?

  • A. More species means larger total population in the ecosystem
  • B. Greater variety of species increases chances of survival through adversities and allows better adaptation to environmental change ✓
  • C. Biodiversity reduces natural calamities like floods and earthquakes
  • D. More species means more forests and less human interference

Answer: B — High biodiversity provides redundancy—if one species fails, others can perform similar functions—and increases adaptive capacity to environmental change.

Q6. According to the study material, what percentage of species that have ever lived on Earth are today extinct?

  • A. 50%
  • B. 75%
  • C. 90%
  • D. 99% ✓

Answer: D — The material states that 99 percent of the species that have ever lived on Earth are today extinct, reflecting the long evolutionary history.

Q7. The economic role of biodiversity includes all of the following EXCEPT:

  • A. Providing food crops and livestock
  • B. Supplying medicinal and cosmetic resources
  • C. Regulating atmospheric oxygen and carbon dioxide levels ✓
  • D. Providing forest and fish resources

Answer: C — Regulating atmospheric gases is an ecological function, not an economic role; economic role refers to resources extracted for human use.

Q8. Which natural calamity is mentioned in the study material as a cause of biodiversity loss?

  • A. Deforestation only
  • B. Volcanic eruptions and forest fires ✓
  • C. Pesticide application only
  • D. Human population growth only

Answer: B — The material explicitly lists volcanic eruptions, forest fires, earthquakes, floods, and droughts as natural calamities causing biodiversity loss.

Q9. Assertion (A): Every species, when extracting its needs from an ecosystem, also contributes something useful to other organisms. Reason (R): Each species performs specific functions that are important for ecosystem function and human survival. Choose the correct option:

  • A. Both A and R are correct, and R is the correct explanation of A ✓
  • B. Both A and R are correct, but R is not the correct explanation of A
  • C. A is correct but R is incorrect
  • D. A is incorrect but R is correct

Answer: A — Both statements are true and logically connected: species contribute to ecosystems because each performs specific functions essential for ecosystem stability.

Q10. If a tropical rainforest region spanning 1 million square kilometers contains species richness S, and this region is one-tenth of the world's total tropical forest area, approximately what fraction of Earth's total species would be present in this 1 million square kilometer region, given that tropical forests occupy one-fourth of Earth's total land area and hold 50% of all species?

  • A. 5% of Earth's total species ✓
  • B. 10% of Earth's total species
  • C. 50% of Earth's total species
  • D. Cannot be determined from the given information

Answer: A — If tropical forests (1/4 of Earth) hold 50% of species, this 1 million km² is 1/10 of tropical forests, so it holds approximately 1/10 × 50% = 5% of Earth's total species.

Flashcards

What is biodiversity in simple terms?

Biodiversity is the number and variety of organisms (plants, animals, micro-organisms) found within a specified geographic region.

Name the three levels of biodiversity.

The three levels are genetic diversity (variation within species), species diversity (number of species in an area), and ecosystem diversity (variety of habitats and ecological processes).

What is genetic diversity and why is it important?

Genetic diversity refers to variations of genes within a species; it is essential for healthy breeding and survival of a population.

What are biodiversity hotspots?

Biodiversity hotspots are areas that are exceptionally rich in species diversity compared to other regions.

What percentage of Earth's species are found in tropical forests?

Tropical forests contain approximately 50 percent of the species on Earth despite occupying only one-fourth of the world's total land area.

What is the ecological role of biodiversity?

Biodiversity's ecological role is that species perform various functions—capturing energy, decomposing materials, cycling nutrients, and regulating climate—which maintain ecosystem stability.

How does high biodiversity affect ecosystem stability?

Higher biodiversity in an ecosystem increases the chances of species survival through adversities and makes the ecosystem more productive and resilient to environmental change.

Name three natural calamities that cause loss of biodiversity.

Earthquakes, floods, volcanic eruptions, forest fires, and droughts are natural calamities that damage flora and fauna and reduce biodiversity.

What is agro-biodiversity?

Agro-biodiversity is crop diversity—the variety of cultivated plants used by humans for food and agricultural purposes.

Why has biodiversity declined since humans emerged on Earth?

Since human emergence, biodiversity has declined rapidly due to overuse of resources, habitat destruction, deforestation, pollution, and species overexploitation.

Important Board Questions

Define biodiversity and state how it relates to evolution. [2 marks]

Define biodiversity as number and variety of organisms in a region; mention that current biodiversity is result of 2.5–3.5 billion years of evolution and continuous change.

Explain the ecological role of biodiversity with an example. How does loss of biodiversity affect ecosystem stability? [5 marks]

State that species capture energy, decompose materials, cycle nutrients, and regulate climate; provide one example (e.g., bees pollinating crops or earthworms enriching soil); then explain that higher biodiversity increases ecosystem resilience and productivity, while loss of species decreases the system's ability to maintain itself during adversities.

Discuss the causes of biodiversity loss and explain why tropical forests are particularly vulnerable to this loss. What are the implications for global biodiversity conservation? [6 marks]

Causes: human population growth leading to resource overexploitation, deforestation, natural calamities, and pollution; tropical vulnerability: occupy 1/4 of land but hold 50% of species, so deforestation there devastates global biodiversity; implications: need for urgent conservation, habitat protection, and sustainable resource use to prevent mass extinction and maintain ecosystem functions that humans depend on.

Assertion-Reason Questions for Biodiversity and Conservation

Q1. Assertion (A):

Biodiversity is distributed evenly across all regions of the Earth.

Reason (R):

Tropical regions receive more solar energy and water, which are the basic inputs for weathering and vegetation diversity.

Answer: D — A is false but R is true — Both the assertion and reason are false. The chapter clearly states 'Biodiversity is not found evenly on the earth. It is consistently richer in the tropics. As one approaches the polar regions, one finds larger and larger populations of fewer and fewer species.' The assertion is directly contradicted by the text.

Q2. Assertion (A):

Tropical rainforests occupy approximately one-fourth of Earth's total area but contain 50 percent of all species on Earth.

Reason (R):

This is because tropical forests receive more solar energy and water, leading to weathering processes that support diverse vegetation.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason correctly explains why tropical forests have disproportionately high species concentration. The chapter connects weathering, energy, and water inputs to the creation of weathering mantles that support diverse vegetation, particularly in tropical regions.

Q3. Assertion (A):

The average half-life of a species is estimated to be between 1 to 4 million years, meaning most species eventually become extinct.

Reason (R):

This demonstrates that extinction is a natural evolutionary process, though current extinction rates due to human activity far exceed natural rates.

Answer: B — Both A and R are true, but R is NOT the correct explanation of A — Both statements are true, but the reason does not correctly explain the assertion. The assertion is simply stating a fact about species lifespan, while the reason adds context about human-caused extinction rates, which is not the explanation for why species have this particular half-life. The half-life reflects natural evolutionary timescales, not current extinction rate comparisons.

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Case-Based Questions (CBQ) for Biodiversity and Conservation

Case Study:

The Western Ghats of India are recognized as one of the world's biodiversity hotspots, supporting an estimated 5,000 plant species, 500 bird species, and numerous endemic species found nowhere else on Earth. The region receives high rainfall from the southwest monsoon and has a complex topography with varied elevation zones. However, researchers report that deforestation for agricultural expansion, tea and coffee plantations, and human settlements has reduced the original forest cover from 95% to approximately 30% over the past 200 years. Species loss in the Western Ghats is estimated at 2-3% per decade, with several endemic species now classified as critically endangered. The remaining fragmented forest patches face increased pressure from poaching, invasive species, and climate change impacts.

Q1. According to the passage, what are the primary factors contributing to biodiversity loss in the Western Ghats?

  • A. Only natural calamities like floods and earthquakes
  • B. Deforestation, agricultural expansion, human settlements, poaching, invasive species, and climate change ✓
  • C. Exclusively invasive species from other continents
  • D. Primarily the natural extinction cycle mentioned in the chapter

Answer: B

Q2. Why are the Western Ghats considered a biodiversity hotspot, and what role does rainfall play in this designation?

  • A. Because they have the largest human population in India
  • B. Because they contain high species diversity with many endemic species, and high rainfall provides the water input necessary for weathering and vegetation diversity ✓
  • C. Because they have the oldest rocks in India
  • D. Because they are situated at the highest elevation of any Indian mountain range

Answer: B

Q3. If species loss continues at the current rate of 2-3% per decade in the Western Ghats, and the region currently supports approximately 5,000 plant species, approximately how many plant species would remain after 20 years at a 2.5% loss rate per decade?

  • A. Approximately 4,625 species
  • B. Approximately 3,750 species
  • C. Approximately 4,400 species ✓
  • D. Approximately 2,500 species

Answer: C

Q4. Based on the chapter's discussion of ecosystem stability and species diversity, what consequence might result from the fragmentation of Western Ghats forests into smaller patches?

  • A. Increased ecosystem stability due to reduced species interactions
  • B. No significant change in ecosystem function
  • C. Reduced ecosystem productivity, decreased genetic diversity within populations, and reduced ability of the ecosystem to adapt to environmental changes ✓
  • D. Rapid evolution of new species to fill ecological niches

Answer: C

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