1. Name the three important components of biodiversity.

     (i)   Genetic diversity

     (ii)  Species diversity

     (iii)  Ecological/Ecosystem diversity.

2. How do ecologists estimate the total number of species present in the world ?

     Bilologists make a statistical comparison of the temperate tropical species richness of an exhaustively studied group of insects and extrapolate this ratio to other groups of animals and plants to reach to the total number of species on earth.

3. Give three hypotheses for explaining why tropics show greatest levels of species richness.

     (i)  Temperate areas have undergone frequent glaciation in the post, whereas no such disturbance occured in the tropics

     (ii)  Tropical environments are relatively more constant, which lead to a greater species diversity

     (iii) Availability of more solar energy in tropics, which contributes to higher productivity and in turn to greater diversity.

4. What is the significance of the slope of regression in a species-area relationship ?

     Steeper slope of regression of an area indicates species richness.

5. What are the major causes of species losses in a geographical region ?

     (i) Habitat loss and fragmentation

     (ii) Over exploitation

     (iii) Alien species invasions

     (iv) Co-extinctions.

6. How is biodiversity important for ecosystem functioning ?

     (i) Rich biodiversity provides stability to the ecosystem 

     (ii) contributes to higher productivity

     (iii) essential for ecosystem health.

7. What are sacred groves ? What is their role in conservation ?

     Sacred groves are forest patches around places of worship which are held in high esteem by tribal communities due to their religious sanctity. These groves protect many endemic species which are rare or have become extinct elsewhere, can be seen to flourish here.

8. Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem ?

     Plant cover protects the soil from wind and water erosion. It also reduce runoff rainwater, so that flood water is rarely formed.

9. The species diversity of plants (22 per cent ) is much less than that of animal (72 per cent ). What could be the explanations to how animals achieved greater diversification ?

     The higher percentage of species diversity among animals is due to their movements to diverse habitats, as a result more evolutionary changes occurred in animals than plants.

10. Can you think of a situation where we deliberately want to make a species extinct ? How would you justify it ?

    One can think of deliberate extinction of a species, when the same becomes nuisance. However, such extinction will not be justified, because a species which seems to be a nuisance toady, may prove useful in the future.