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Biodiversity And Conservation

Biodiversity and Conservation - Complete NEET Guide with Diagrams & Practice Questions

Table of Contents

  1. Introduction
  2. Key Concepts
  3. Important Formulas & Equations
  4. Memory Techniques (Mnemonics)
  5. Previous Year Questions (NEET)
  6. Key Takeaways for Quick Revision

Introduction

The sheer variety of life on Earth, from tiny microbes to giant blue whales, is what we call biodiversity. This chapter, "Biodiversity and Conservation," explores the richness of life, the patterns it follows, the alarming rate at which we are losing it, and the urgent need to protect it. As the concluding chapter of the Ecology unit, it is of immense importance for the NEET exam, contributing 2-3 questions annually.

Questions from this chapter are often direct and fact-based, testing your knowledge of conservation strategies (in-situ and ex-situ), biodiversity hotspots, the causes of biodiversity loss ("The Evil Quartet"), and the species-area relationship. This guide will provide a structured overview of all these critical topics, complete with diagrams and memory aids, to ensure you can confidently answer any question and secure valuable marks.

Key Concepts

1. Levels of Biodiversity

The term biodiversity was popularized by the sociobiologist Edward Wilson. It describes the combined diversity at all levels of biological organisation. The three most important levels are:

  1. Genetic Diversity: Diversity shown by a single species at the genetic level over its distributional range.
    • Example: The medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges shows genetic variation in the potency and concentration of the active chemical reserpine.
    • Example: India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.
  2. Species Diversity: The diversity at the species level.
    • Example: The Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
  3. Ecological Diversity: The diversity at the ecosystem level.
    • Example: India, with its deserts, rain forests, mangroves, coral reefs, and wetlands, has a greater ecosystem diversity than a Scandinavian country like Norway.

2. Global and Indian Biodiversity Data

  • According to the IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million.
  • A more scientifically sound estimate by Robert May places the global species diversity at about 7 million.
  • Global Species Distribution:
    • More than 70% of all species recorded are animals.
    • Among animals, insects are the most species-rich group, making up more than 70% of the total.
    • The number of fungi species is more than the combined total of all vertebrate species (fishes, amphibians, reptiles, and mammals).

Figure: Pie charts representing global biodiversity, showing the proportionate number of species of major taxa.

  • India's Biodiversity:
    • Despite having only 2.4% of the world's land area, India has an impressive 8.1% of the global species diversity.
    • This makes India one of the 12 mega-diversity countries of the world.

3. Patterns of Biodiversity

  1. Latitudinal Gradients:

    • Rule: Species diversity decreases as we move away from the equator towards the poles.
    • Example: Colombia (near the equator) has ~1,400 bird species, while New York (41° N) has 105, and Greenland (71° N) has only 56.
    • The Amazonian rain forest in South America has the greatest biodiversity on Earth.
    • Reasons for Higher Tropical Diversity:
      1. More Evolutionary Time: Tropical latitudes have remained relatively undisturbed for millions of years, allowing for longer evolutionary time for species diversification.
      2. Constant Environment: Tropical environments are less seasonal and more predictable, promoting niche specialisation and leading to greater species diversity.
      3. Higher Productivity: More solar energy is available in the tropics, which contributes to higher productivity and, in turn, greater diversity.

  2. Species-Area Relationship:

    • Observation by Alexander von Humboldt: Within a region, species richness increases with increasing explored area, but only up to a limit.
    • The relationship is a rectangular hyperbola.
    • On a logarithmic scale, the relationship is a straight line described by the equation: log S = log C + Z log A
    • Z (Slope of the line/Regression Coefficient): The value of Z typically lies in the range of 0.1 to 0.2 for smaller areas, regardless of the taxonomic group or region. For very large areas like entire continents, the slope is much steeper, with Z values in the range of 0.6 to 1.2.

Figure: Graph showing the Species-Area Relationship. The curve is a rectangular hyperbola, which becomes a straight line on a logarithmic scale.

4. Importance of Species Diversity to the Ecosystem

  • Stability: Ecologist David Tilman's experiments showed that plots with more species exhibited less year-to-year variation in total biomass (more stable) and higher productivity.
  • Rivet Popper Hypothesis: Proposed by Stanford ecologist Paul Ehrlich to explain the importance of biodiversity.
    • Analogy: An airplane (ecosystem) is held together by thousands of rivets (species).
    • If every passenger starts taking a rivet home (causing species to become extinct), the plane may not be affected initially.
    • However, as more rivets are removed, the plane becomes dangerously weak.
    • The loss of a rivet on a wing (keystone species) is a more serious threat than the loss of a rivet on a seat.

5. Loss of Biodiversity

The world is facing an accelerated rate of species extinction, largely due to human activities. This is often called the Sixth Extinction.

  • The Evil Quartet: The four major causes of biodiversity loss.
CauseDescriptionExamples
Habitat loss & FragmentationMost important cause. Destruction of natural habitats.Clearing of tropical rainforests (Amazon) for agriculture. Fragmentation affects animals with large territories or migratory habits.
Over-exploitationHarvesting renewable resources at a rate faster than they can be replenished.Steller's sea cow, Passenger pigeon. Over-harvesting of marine fish.
Alien Species InvasionsIntroduction of a new species into a habitat, which turns invasive and causes the decline of indigenous species.Nile perch introduced in Lake Victoria led to the extinction of >200 cichlid fish species. Invasive weeds like Parthenium and Eichhornia.
Co-extinctionsWhen a species becomes extinct, plant and animal species associated with it in an obligatory way also become extinct.A host fish and its unique parasites. A co-evolved plant-pollinator mutualism.

6. Biodiversity Conservation

  • Reasons for Conservation:

    1. Narrowly Utilitarian: Direct economic benefits from nature, such as food, firewood, fiber, industrial products, and medicines (bioprospecting).
    2. Broadly Utilitarian: The role biodiversity plays in providing ecosystem services, such as oxygen production, pollination, and aesthetic value. The Amazon forest produces 20% of the total oxygen in the Earth's atmosphere.
    3. Ethical: Every species has an intrinsic value, and we have a moral duty to protect them for future generations.

  • Conservation Strategies:

    1. In-situ Conservation (On-site): Protecting species in their natural habitat. The entire ecosystem is protected.

      • Biodiversity Hotspots: Regions with very high levels of species richness and a high degree of endemism (species found nowhere else). Initially 25, now there are 34 hotspots in the world. India has 3 hotspots: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya.
      • Protected Areas: Biosphere Reserves (18 in India as of recent data), National Parks (100+), and Wildlife Sanctuaries (500+).
      • Sacred Groves: Tracts of forest set aside and given total protection based on religious and cultural traditions (e.g., in Khasi and Jaintia Hills of Meghalaya).

    2. Ex-situ Conservation (Off-site): Protecting threatened species outside their natural habitat in special settings.

      • Methods: Zoological parks, botanical gardens, and wildlife safari parks.
      • Advanced Techniques:
        • Cryopreservation: Preserving gametes of threatened species in a viable condition at very low temperatures (-196°C in liquid nitrogen).
        • Seed Banks: Storing seeds for long periods.
        • In-vitro fertilization and tissue culture propagation.

  • International Efforts:

    • The Earth Summit (Convention on Biological Diversity) held in Rio de Janeiro, 1992.
    • The World Summit on Sustainable Development held in Johannesburg, 2002, which pledged to significantly reduce the rate of biodiversity loss.

Important Formulas & Equations

  • Species-Area Relationship Equation: S = CA^Z

    • S: Species richness
    • A: Area
    • C: Y-intercept
    • Z: Slope of the line (regression coefficient)

  • Logarithmic form of the Equation: log S = log C + Z log A

Memory Techniques (Mnemonics)

  • The Evil Quartet: Remember "HOAC" (sounds like "hoax").
    • Habitat Loss & Fragmentation
    • Over-exploitation
    • Alien Species Invasion
    • Co-extinction
  • India's Biodiversity Hotspots: Remember "HI-W"
    • Himalaya
    • Indo-Burma
    • Western Ghats (& Sri Lanka)
  • Conservation Strategies:
    • In-situ: "IN the situation" (natural habitat).
    • Ex-situ: "EXit the situation" (outside natural habitat).

Previous Year Questions (NEET)

Q1. The historic Convention on Biological Diversity held in Rio de Janeiro in 1992 is known as: (NEET 2022) a) The Earth Summit b) The G-8 Summit c) The World Summit d) CITES Convention

Explanation: The historic Convention on Biological Diversity, held in Rio de Janeiro in 1992, is popularly known as The Earth Summit. Answer: (a) The Earth Summit

Q2. Which of the following is an example of an alien species invading a new ecosystem? (NEET 2021) a) Introduction of Nile Perch into Lake Victoria in East Africa. b) Introduction of water hyacinth into India. c) Introduction of African catfish into Indian rivers. d) All of the above.

Explanation: All three examples—Nile perch in Lake Victoria, water hyacinth in India, and African catfish in Indian rivers—are classic textbook cases of alien species invasions causing harm to native ecosystems. Answer: (d) All of the above.

Q3. According to Robert May, the global species diversity is about: (NEET 2020) a) 1.5 million b) 20 million c) 50 million d) 7 million

Explanation: While IUCN has recorded over 1.5 million species, Robert May's more conservative and scientifically sound estimate places the global species diversity at approximately 7 million. Answer: (d) 7 million

Q4. Which of the following is not a method of in-situ conservation of biodiversity? (NEET 2019) a) Biosphere Reserve b) Wildlife Sanctuary c) Botanical Garden d) Sacred Grove

Explanation: Biosphere reserves, wildlife sanctuaries, and sacred groves are all methods of in-situ conservation, where species are protected within their natural habitats. Botanical gardens are a method of ex-situ conservation, where species are protected outside their natural habitats. Answer: (c) Botanical Garden

Key Takeaways for Quick Revision

  • Biodiversity exists at three levels: Genetic, Species, and Ecological.
  • The two major patterns of biodiversity are the Latitudinal Gradient (diversity decreases from equator to poles) and the Species-Area Relationship (S = CA^Z).
  • The four main causes of biodiversity loss are the Evil Quartet: Habitat loss, Over-exploitation, Alien species invasions, and Co-extinctions.
  • We must conserve biodiversity for narrowly utilitarian (direct economic benefits), broadly utilitarian (ecosystem services), and ethical reasons.
  • Conservation methods are of two types: In-situ (hotspots, national parks, sacred groves) and Ex-situ (zoos, botanical gardens, cryopreservation).
  • India is a mega-diversity country with 3 of the world's 34 biodiversity hotspots.
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