question_answer

(i) Define thermal pollution and explain why thermal pollution of water is harmful to aquatic animals?

(ii) The use of pesticides DDT is discouraged since this chemical is found in human body. How does this chemical enter the body?

OR

List any 4 causes of loss of biodiversity. Explain any 2 of them.

 

Answer:

(i)  Rise in temperature of air and water to harmful level due to heat from power plant, automobiles and industries are called thermal pollution. Warm water can hold much less dissolved oxygen than cold water. This deoxygenation of water may kill the fish & other aquatic animals. Rise in temperature spreads up metabolism, inducing \[{{O}_{2}}\]requirement.

(ii) DDT enters the food chain. The farmers spray DDT pesticides on their crops to protect them from pest. Some of this DDT mixes with soil and goes into water bodies. The crop plants along with minerals and water absorb this DDT. When human beings consume these crop plants or their products, then DDT present in them enters human body.

OR

Reasons for loss of biodiversity are

1. Habitat loss or destruction

2. Habitat fragmentation

3. Introduction of exotic species

4. Over exploitation of existing species.

Habitat loss of destruction - Expanding population & development require more industrial areas, extension of present towns and cities, more area for agriculture, new road canals, dams etc. All these activities will result in destruction of natural habitat.

Destruction of habitat is the primary cause of extinction of species. Grasslands were converted into agricultural lands during colonisation of America. Newzealand abounded in wetlands.

Habitat fragmentation - It is the breaking of habitat into smaller patches due to development of agriculture, water bodies and other changes. Forest patches having croplands, orchards plantation and urban settlements on their outskirts are examples of fragmented habitat. Habitat fragmentation results in disruption of complex interaction amongst species, destruction of species in the cleared regions, annihilation of species restricted to deeper undisturbed parts of forest & decreased biodiversity in the habitat fragments.