Ecosystem is an interaction between the various components of nature or environment ( biotic and abiotic )example biotic.. plants and other living organisms and abiotic...Air water light etc... ..just don't use the plastic bags... ..reduce use of air conditioners, refrigerators, which release CFC.. ....don't use wood dung cakes etc as fuel. . ...lessen the use of private vehicles and use public vehicles...
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Ecosystem is a self-contained system or a biological community of living things (or biotic components) and their non-living (or abiotic components) environment which surrounds them. 

Infact, we human beings are the only organisms in the ecosystem who can change/alter the environment for fulfilling our greeds, damaging its balance and health. The various threats to the balance of the ecosystem include deforestation, hunting & poaching, extinction of species & imbalance in food chain, rapid climatic changes etc. Neccessary steps must be taken in order to overcome such threats.

Hope this helps :)