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living components, from microorganisms to plants and animals tend to concentrate them in pockets. Thus, water hyacinth, considered a weed, (what is a weed?) picks up a large number of hazardous compounds, like mercury, arsenic etc. from ponds and these get concentrated in the plant tissues. NASA carried out studies to use these for effluent treatment. This is the good side of this effect. The bad side is, fish do the same for effluents which enter our system when we the fish. 2) Theory of Evolution: Though termed as a theory, it is an established law of nature, though not as mathematically precise as the law of Entropy. Living things undergo "natural selection" and only those that "match" with the environment survive. The others get extinct. This is why we find in nature so many creatures that beautifully blend into the surroundings. Boiling water springs breed microbes that need hot water for growth, Salt water breeds "salt loving" or halophilic organisms. Oxygen lacking environment encourage life forms that can do without elemental oxygen, (it can be even toxic to them) but use oxygen from chemical compounds in the environment. But all the evolutionary changes are very slow, compared to the life span of the human race and the history of our civilisation. They are therefore, unacceptable to us as methods of change. Mankind has produced its own cultural or intellectual evolution, which could also eliminate the incompatibles. Therefore, when we talk of environmental risk, we do not mean risk to the planet, but to the human race and the life species it likes. The mosquitoes, the flies, the smallpox virus and cockroaches are not in our "environment" list. I have no qualms about being selfish in wanting to protect human and other friendly species. But, would someone want to extend the same principles to ethnic groups within the human race? Rural Development Through Education System 152