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Biodiversity and Conservation

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

Chapter Notes

BIODIVERSITY AND CONSERVATION

DEFINITION AND BASIC CONCEPT

**Biodiversity** is derived from two words: **Bio** (life) and **diversity** (variety). It refers to the **number and variety of organisms found within a specified geographic region**. More comprehensively, biodiversity encompasses the varieties of plants, animals, and micro-organisms, the genes they contain, and the ecosystems they form. It relates to the **variability among living organisms on Earth, including variability within and between species and within and between ecosystems**.

Biodiversity is our **living wealth** and represents the result of **2.5 to 3.5 billion years of evolutionary history**. Before human emergence, Earth supported far greater biodiversity than exists today. The current estimates of global species numbers vary from **2 million to 100 million, with 10 million being the best estimate**. However, approximately **99 percent of species that have ever lived on Earth are today extinct**, with the average half-life of a species estimated at **one to four million years**.

DISTRIBUTION OF BIODIVERSITY

Biodiversity is **not distributed evenly across Earth**. Key patterns include:

  • **Tropical regions are richest in biodiversity** — tropical forests occupy only about one-fourth of Earth's total area but contain approximately **50 percent of all species on Earth**
  • **As one approaches polar regions, populations of individual species increase while the total number of species decreases** — fewer and fewer species but larger populations
  • **Biodiversity is consistently richer in tropical zones** than in temperate or polar regions
  • New species are regularly discovered; estimates suggest **about 40 percent of freshwater fishes from South America are not yet classified**

    • THREE LEVELS OF BIODIVERSITY

    Biodiversity operates at three distinct hierarchical levels:

    #### (1) GENETIC DIVERSITY

    **Genetic diversity** refers to the **variation of genes within a species**.

  • **Genes are the basic building blocks of various life forms**
  • Groups of individual organisms possessing certain similarities in physical characteristics are called **species**
  • Example: All human beings belong to the species **Homo sapiens**, yet show considerable genetic variation in height, color, skin pigmentation, and physical appearance
  • **Genetic diversity is essential for healthy breeding of population** — it ensures adaptability and resilience
  • A population with high genetic diversity has greater chances of survival during environmental stress or disease outbreaks

    • #### (2) SPECIES DIVERSITY

    **Species diversity** refers to the **variety and number of species in a defined area**.

  • Measured through three parameters: **richness** (total number of species), **abundance** (population sizes), and **types** (composition of species groups)
  • **Some areas are richer in species than others**
  • Areas exceptionally rich in species diversity are called **hotspots of diversity** (as shown in Figure 14.5)
  • Example: Madagascar contains approximately **85 percent of plants and animals found nowhere else in the world**, making it a supreme biodiversity hotspot
  • The Hawaiian Islands contain many unique endemic species threatened by introduced (exotic) species and land development

    • #### (3) ECOSYSTEM DIVERSITY

    **Ecosystem diversity** encompasses the **broad differences between ecosystem types and the diversity of habitats and ecological processes within each ecosystem type**.

  • **Boundaries of communities (associations of species) and ecosystems are not rigidly defined**, making demarcation of ecosystem boundaries difficult and complex
  • Relates to the variety of habitats and the ecological processes occurring within them
  • Example: Different ecosystem types include grasslands, sholas (tropical forests on hills), deserts, wetlands, coral reefs, and marine ecosystems
  • Figure 14.1 shows grasslands and sholas in Indira Gandhi National Park, exemplifying ecosystem diversity within a single protected area

    • IMPORTANCE OF BIODIVERSITY

    Biodiversity plays three critical roles in nature and human existence:

    #### ECOLOGICAL ROLE

  • **Every organism performs some function in an ecosystem** — no ecosystem evolves and sustains without reason
  • Each organism, besides extracting its needs, also **contributes something useful to other organisms**
  • **Species capture and store energy, produce and decompose organic materials, help cycle water and nutrients, fix atmospheric gases, and help regulate climate**
  • **A more diverse ecosystem has better chances for species to survive adversities and attacks**, making it more productive
  • **Loss of species decreases the ecosystem's ability to maintain itself** — ecosystem stability depends on biodiversity
  • **An ecosystem with high biodiversity has greater chance of adapting to environmental changes** — similar to species with high genetic diversity
  • **The greater the variety of species in an ecosystem, the more stable that ecosystem is likely to be**

    • #### ECONOMIC ROLE

  • **Biodiversity is an important resource in human day-to-day life**
  • **Crop diversity** (also called **agro-biodiversity**) is a crucial component
  • Biodiversity serves as a **reservoir of resources for manufacturing food, pharmaceutical, and cosmetic products**
  • Important economic commodities supplied by biodiversity include: **food crops, livestock, forests, fish, medicinal resources, and timber**
  • This concept of biological resources as economic commodity has paradoxically caused deterioration of biodiversity through over-exploitation
  • Generated new conflicts over **division and appropriation of natural resources**

    • #### SCIENTIFIC ROLE

  • **Each species provides clues about how life evolved and will continue to evolve**
  • Helps understand **how life functions and the role of each species in sustaining ecosystems** of which humans are also a part
  • **It is our ethical responsibility to consider that each species has an intrinsic right to exist** — morally wrong to voluntarily cause extinction
  • **The level of biodiversity is a good indicator of the state of human relationships with other living species**
  • **The concept of biodiversity is an integral part of many human cultures**

    • CONNECTION TO PHYSICAL GEOGRAPHY

    The chapter explicitly links biodiversity to geomorphic processes:

  • **Weathering mantle depth varies across different climatic zones** (see Figure 5.2, Chapter 5)
  • **Weathering mantle is the basis for vegetation diversity and hence biodiversity**
  • **Areas rich in solar energy and water inputs show wide spectrum of biodiversity** — tropical regions receive both high solar radiation and precipitation
  • Climate determines the depth of weathering, soil formation, and vegetation type, which collectively determine biodiversity patterns

    • LOSS OF BIODIVERSITY

    #### CAUSES OF BIODIVERSITY LOSS

    **Primary causes** include:

  • **Growth in human population** has dramatically increased natural resource consumption rates over recent decades
  • **Over-exploitation of resources** — resources extracted faster than they can regenerate
  • **Deforestation** has become rampant, particularly in tropical regions
  • **Tropical regions occupy only one-fourth of Earth's area but contain three-fourths of world's human population**, creating intense pressure on resources
  • **Natural calamities** — earthquakes, floods, volcanic eruptions, forest fires, droughts cause damage to flora and fauna
  • **Pesticides and pollutants** — hydrocarbons and toxic heavy metals destroy weak and sensitive species
  • **Introduction of exotic species** — **species not naturally inhabiting a local habitat but introduced into the system**, causing damage to natural biotic communities
  • **Hunting and poaching** — animals like tigers, elephants, rhinoceros, crocodiles, minks, and birds hunted mercilessly for horn, tusks, hides, resulting in **endangered species classification**

    • THREATENED SPECIES CATEGORIES

    The **International Union for the Conservation of Nature and Natural Resources (IUCN)** classifies threatened species into three categories:

    #### ENDANGERED SPECIES

  • **Species in danger of extinction**
  • **IUCN publishes information about endangered species worldwide as the Red List of threatened species**
  • Example: Red Panda (Figure 14.2)
  • Require immediate intervention and protection

    • #### VULNERABLE SPECIES

  • **Species likely to be in danger of extinction in near future** if threatening factors continue
  • **Population has reduced greatly** — survival not assured
  • Require preventive conservation measures before critical decline

    • #### RARE SPECIES

  • **Population is very small in the world**
  • **Confined to limited areas or thinly scattered over wider area**
  • Though not currently endangered, face extinction risk if conditions deteriorate
  • Example: **Humboldtia decurrens Bedd** — highly rare endemic tree of Southern Western Ghats (Figure 14.3)

    • CONSERVATION OF BIODIVERSITY

    #### IMPORTANCE OF CONSERVATION

  • **Biodiversity is important for human existence**
  • **All forms of life are so closely interlinked that disturbance in one causes imbalance in others**
  • **If plant and animal species become endangered, they cause environmental degradation potentially threatening human existence itself**
  • Conservation ensures sustainable use of biological resources for future generations

    • #### INTERNATIONAL CONVENTIONS

    **Rio de Janeiro Earth Summit (June 1992):**

  • **Government of India signed the Convention of Biodiversity** along with **155 other nations**
  • Established global framework for biodiversity conservation

    • **World Conservation Strategy recommendations** for biodiversity conservation:

    1. **Make efforts to preserve endangered species**

    2. **Prevention of extinction requires proper planning and management**

    3. **Preserve varieties of food crops, forage plants, timber trees, livestock, animals, and their wild relatives**

    4. **Each country should identify habitats of wild relatives and ensure their protection**

    5. **Habitats where species feed, breed, rest, and nurse young should be safeguarded and protected**

    6. **International trade in wild plants and animals should be regulated**

    #### NATIONAL CONSERVATION MEASURES

    **The Wild Life (Protection) Act, 1972:**

  • Government of India enacted this act to **protect, preserve, and propagate variety of species within natural boundaries**
  • Under this act, **national parks and sanctuaries were established** and **biosphere reserves were declared**
  • Details of India's biosphere reserves are provided in "India: Physical Environment" (NCERT, 2006)

    • #### BIODIVERSITY HOTSPOTS

    **Mega diversity centres** — **12 countries with large world species diversity**, located in tropical regions:

  • **Mexico, Colombia, Ecuador, Peru, Brazil, Democratic Republic of Congo, Madagascar, China, India, Malaysia, Indonesia, and Australia**

    • **Hotspots identification:**

  • **IUCN (International Union for Conservation of Nature and Natural Resources) identifies certain areas as biodiversity hotspots** to concentrate conservation resources on most vulnerable areas
  • **Hotspots are defined according to their vegetation** — plants determine primary productivity of ecosystems
  • **Most hotspots rely on species-rich ecosystems for food, firewood, cropland, and timber income**

    • **Example:** Madagascar hotspot contains **85 percent endemic species** found nowhere else globally.

    #### FUTURE CONSERVATION STRATEGY

  • **Urgent need to educate people to adopt environment-friendly practices**
  • **Reorient activities so development is harmonious with other life forms and sustainable**
  • **Conservation with sustainable use is possible only with involvement and cooperation of local communities and individuals**
  • **Development of institutional structures at local levels is necessary**
  • **Critical problem is not merely conservation of species or habitat, but continuation of conservation process itself**

    • EXAM-IMPORTANT POINTS

  • Biodiversity distribution is uneven — richer in tropics, decreases toward poles
  • Three hierarchical levels: genetic, species, and ecosystem diversity
  • Tropical forests contain 50 percent of Earth's species despite occupying only 25 percent of area
  • IUCN classifies threatened species into three categories: endangered, vulnerable, and rare
  • Earth Summit (1992) in Rio de Janeiro established Convention of Biodiversity
  • Wild Life (Protection) Act, 1972 established India's national parks, sanctuaries, and biosphere reserves
  • 12 mega diversity countries identified; India is one of them
  • Conservation requires integration of scientific, economic, ecological, and ethical considerations
  • Loss of biodiversity causes environmental degradation threatening human survival

    • 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.

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