Ecology is science of how living creatures and plants exist together and depend on each other and on the local environment. Where an environment is undisturbed,the ecology of an area is in balance,but if a creature is exterminated or and alien species introduced, then the ecology of the district will be upset-in other world,the balance of nature will be disturbed.Man is a part of the environment and has done more to upset the ecology during his short span on earth than any other living creature.He has done this by his ignorance, his greed,his thorughtless folly and his wanton wastefulness.he had poisoned the atmosphere and polluted both land and water. He has squandered the earth's natural resources with no thought for the future,and has thought out the most devastaing ways of killing his fellow man-and every other sort of life at the same time.