Alternations in Environment

Manipulation of the environment at the hands of man has occurred through physical conditions, change in biotic community and depletion and degradation of natural resources

1. Physical conditions.
Through his notorious acts man has disturbed physical conditions of environment. He has cut down forests for wood, farm land etc. He has also put grasslands to use. Big factories and dug many canals, lakes and tanks for irrigation and transport and drains for sewage. Though these are great chievements but at a high price, ecological balance in nature has been disturbed.

These animals are Inquilines. Many cultivated plants like cabbage, tomato, maize, wheat also require human help for their cultivation. These are called Cultigens.
Man has transplanted many organism to new habitat.
(i) Parthenium hysterosphorus (carrot grass) introduced in India since 1956.
(ii) Clover and bumble bee to New Zealand and Merino sheep to Australia.
(iii) As agents of biological control-Cochineal insect to Australia to control Opuntia.
(iv) Water hyacinth to India as a material of fancy.