(a) Biodiversity refers to the variety of organisms existing on the earth, their interrelationships, and their relationship with the environment. We should save biodiversity because it is very important for the environment and all the living organisms present on earth. It maintains the balance in the ecosystem as both plants and animals depend on each other for their survival.

(b) People who live near the forest depend on the forest for certain resources that are important for their livelihood. So, they can hunt the animals that lived in the protected forest. The animals also feel threatened by the presence of the human population around them. This results in the killing of wild animals and selling their parts for money. 

(c) Forest is the source of food and shelter for tribal people. It provided fruits, vegetables, fuels fodder, and other resources that are essential for the livelihood of the tribal people. 

(d) Deforestation and Its Causes - Clearing forests by cutting trees on large scale is called deforestation. Causes of deforestation are:

1. The trees in the forest are cut to obtain wood.

2. To get land for building houses, factories, and industries.

3. The trees are cut to get land for cultivation.

The consequences of deforestation are:

1. Increase in the temperature leading to Global Warming

2. Increase level of carbon dioxide in the air

3. Decrease in the underground water level

4. Flood

5. Desertification

6. Animal life is affected by deforestation

(e) The Red Data Book keeps a record of all the endangered animals and plants. It is maintained internationally by an organization. It is also maintained by India. 

(f) Migration is defined as the movement of the organisms or the group of organisms from one to another. The birds which move from extreme cold places to warmer places in winter and go back after the winter is over are called migratory birds. They escape from the extreme cold condition of their natural habitat in order to survive and for the breed (laying eggs).