NCERT Solutions for Class 12 Biology Chapter 15: Biodiversity and Conservation

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    1. Name the three important components of biodiversity.
    Ans.Three components of biodiversity are:
    (a) Genetic diversity
    (b) Species diversity
    (c) Ecological diversity

    2. How do ecologists estimate the total number of species present in the world?
    Ans. Ecologists estimate the total number of species present in the world by statistical comparison between a species richness of a well-studied group of insects of temperate and tropical regions. Then, these ration are extrapolated with other groups of plants and animals to calculate the total species richness present on the earth.

    3. Give three hypothesis for explaining why tropics show greatest levels of species richness.
    Ans. (i) The tropical area have a more stable climate than temperate zones. Local species continues to live in absence of natural disturbances.
    (ii) Warm temperature and high humidity in most tropical areas provide favourable conditions for growth and survival of diverse species.
    (iii) Tropical areas receive more solar energy over year and thus tropical communities are more productive and can support a wide range of species.

    4. What is the significance of the slope of regression in a species-area relationship?
    Ans. Slope of regression in species area relationship products species richness of an area. For a limited area like, a country, it gives a constant value of 0.1 to 0.2 irrespective of the taxonomic group or region. It remains amazingly similar for all those small regions. On the contrary, for measuring species-area relationship over large areas like the entire continents, the slope of regression values in the range of 0.6 to 1.2.

    5. What are the major causes of species losses in a geographical region?
    Ans. The major causes of species losses in a geographical region are as follows:
    (i) Habitat loss and fragmentation.
    (ii) Ov er-exploitation of natural resources
    (iii) Alien species invasions can cause decline or extinction of indigenous species.
    (iv) Co-extinction where if one species get extinct then other dependent species will also get extinct.

    6. How is biodiversity important for ecosystem functioning?
    Ans. Biodiversity is important for ecosystem functioning because,
    (i) It contributes to productivity .
    (ii) It cause more efficient recycling of energy and matter.
    (iii) It has many alternative pathways for survival under diverse conditions.
    (iv) Rich biodiversity provides alternatives available at each trophic level. All organisms are linked in food chains and interact with their abiotic environment in such a way so as to keep the natural cycles going and make the ecosystems self – sustaining units. Disappearance of any link in a food chain will not affect the ecosystem as other alternatives are there.

    7. What are sacred groves? What is their role in conservation?
    Ans. Scared groves: Scared graves are tracts of forest which are regenerated around place of worship. They are found in Rajasthan, Western Ghats of Karnataka and Maharastra.
    Role of sacred graves in conservation:
    (i) Sacred graves help in the protection of many rare, threatened and endemic species of plants and animals found in an area.
    (ii) The process of deforestation is strictly prohibited in this region by tribles.

    8. Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
    Ans. The biotic components of the ecosystem are the living organisms such as plants, animals and microorganisms. Plant roots bind the soil and prevent the erosion by rainwater thereby preventing soil erosion. The roots also make the soil porous, thereby allowing ground water infilteration and preventing floods.

    9. The species diversity of plants (22 per cent) is much less than that of animals (72 per cent). What could be the explanations to how animals achieved greater diversification?
    Ans. Animals have achieved greater diversifications than plants due to following reasons:
    (i) They posses receptors to receive environmental stimuli and show response against them. Most of their receptors are adaptive and ensure their survival in changing environmental conditions.
    (ii) They are mobile and avoid competition. They show niche specialization.
    (iii) They are subjected to loss seasonal and more constant environment.

    10. Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
    Ans. Humans can cause extinction of species through various means. We are trying to eradicate disease causing organisms (e.g., poliovirus) from this world to make this world disease free. Since such micro-organisms are harmful to the human society, such attempt is justified. Further, such micro-organisms are not essential components (producers or decomposers) of any ecosystem, and losing one or few such organisms would not affect the functioning of ecosystem.

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