2024年5月1日发(作者：beatssolo3安卓能用吗)

托福考试

复习

托福阅读TPO15(试题+答案+译文)第2篇:Mass Extinctions物种灭绝

托福阅读原文

【1】Cases in which many species become extinct within a geologically

short interval of time are called mass extinctions. There was one such

event at the end of the Cretaceous period(around 70 million years ago).

There was another, even larger, mass extinction at the end of the Permian

period (around 250 million years ago). The Permian event has attracted

much less attention than other mass extinctions because mostly

unfamiliar species perished at that time.

【2】The fossil record shows at least five mass extinctions in which many

families of marine organisms died out. The rates of extinction happening

today are as great as the rates during these mass extinctions. Many

scientists have therefore concluded that a sixth great mass extinction is

currently in progress.

【3】What could cause such high rates of extinction? There are several

hypotheses, including warming or cooling of Earth, changes in seasonal

fluctuations or ocean currents, and changing positions of the continents.

Biological hypotheses include ecological changes brought about by the

evolution of cooperation between insects and flowering plants or of

bottom-feeding predators in the oceans. Some of the proposed