生命死亡生命.doc

Life and Death and Life
Edgar M﹒Reilly, Jr.
Each moment of each day sees the death of some living thing. We know that each plant and animal, by natural tendency, produces far more seeds and eggs, and seedlings and young, than is necessary to maintain its population. This occurs because each species has an insecure hold on life. Moreover, death is necessary for the survival of life, and the death rate must just about equal the birth rate. If all the seeds and eggs created through the life processes survived and grew to adulthood there could be no life able to continue through this overcrowding.
A pair of American robins nest in one backyard raising two brood of four each. Ten robin where there were two. These pair up and return to equally essful nestlings each year. No matter how much one likes robins, over 90 million birds in one yard at the end of the tenth year would be two much. And there would not be enough worms to feed them.
Nature allows a seeming excess because the difficulties of life restrict survival of both young and old, and the result of this delicate balance is that population rise and fall in small numbers; only rarely do they rise to disastrous millions or fall plete to zero. Both plants and animals may reach ages where there they are no longer able to reproduce, but usually before old age is reached sickness, storm, and slowed reactions to danger will have