生物的辐射演化和绝灭事件

任何生物在其绝灭之前都会程度不同地发生辐射演化,这种辐射演化是由多种因素引起的。辐射演化的结果不仅使生物增强了对环境的适应能力,也增加了对环境的专属性和依赖性,进而也增大了其绝灭的可能性。地质历史时期生物发展的历史,充分体现了生物辐射演化和绝灭事件之间的密切联系。

RADIATION AND MASS EXTINCTION

Most palaeontologists usually stress adaptive radiation following mass extinction. It is a fact undoubtedly. But there is no direct causality between the organism becoming adaptive radiation and the mass extinction itself. The radiation means only that the vacancy left by the disappearing organism are occupaied by other organisms which escaped the mass- extinction or by new ones. In this paper, another aspect of radiation being followed by a mass extinction and having direct causality, is empha- sized. As a matter of fact any taxon more or less has a chance for adaptive radiation before its extinction. During adaptive radiations each taxon becomes specialized for specific habits, special living conditions, special kinds of food etc. The more specialized a texon becomes, the threat of extinction is greater duringth environmental change. The giant panda is an excellent example. It is a common feature of the fossil record that a biota being more conservative with more generalized environment requirements have a greater longevity. It is also true the other way round.