The term food chain was first put forward by British zoologist Elton in 1927. If a toxic substance is absorbed by the lower part of the food chain, such as by grass, although the concentration is very low and does not affect the growth of grass, it is difficult for a rabbit to excrete and accumulate in its body after eating grass; an eagle eats a large number of rabbits. toxic substances will further accumulate in the eagle body. The reason why the American national bird, the bald eagle, is facing extinction is not that it is hunted and killed, but because the harmful chemical D.D.T gradually accumulates in its body, so that the eggs laid are soft shells and cannot hatch.
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Cumulative and magnifying effects of the food chain