- 1、本文档共5页,可阅读全部内容。
- 2、有哪些信誉好的足球投注网站(book118)网站文档一经付费(服务费),不意味着购买了该文档的版权,仅供个人/单位学习、研究之用,不得用于商业用途,未经授权,严禁复制、发行、汇编、翻译或者网络传播等,侵权必究。
- 3、本站所有内容均由合作方或网友上传,本站不对文档的完整性、权威性及其观点立场正确性做任何保证或承诺!文档内容仅供研究参考,付费前请自行鉴别。如您付费,意味着您自己接受本站规则且自行承担风险,本站不退款、不进行额外附加服务;查看《如何避免下载的几个坑》。如果您已付费下载过本站文档,您可以点击 这里二次下载。
- 4、如文档侵犯商业秘密、侵犯著作权、侵犯人身权等,请点击“版权申诉”(推荐),也可以打举报电话:400-050-0827(电话支持时间:9:00-18:30)。
查看更多
托福阅读文章中的物种灭绝
智 课 网 托 福 备 考 资 料
托福阅读文章中的物种灭绝
如今托福阅读的背景知识要求越来越多,托福阅读题材也越来越广
泛,如果大家不能在新托福阅读的复习时对各种资料有一个了解的话考
试的时候会很困难,下面的材料是关于物种的自然灭绝的现象,希望对
大家有帮助。 新托福阅读准备之托福阅读题材:关于物种的自然灭绝
托福阅读原文: Natural selection acts solely through the
preservation of variations in
some way advantageous, which consequently endure. Owing
to the high geometrical
rate of increase of all organic beings, each area is already
fully stocked with
inhabitants; and it follows from this, that as the favoured
forms increase in
number, so, generally, will the less favoured decrease and
become rare. Rarity,
as geology tells us, is the precursor to extinction. We can see
that any form
which is represented by few individuals will run a good
chance of utter
extinction, during great fluctuations in the nature of the
seasons, or from a
temporary increase in the number of its enemies. But we may
go further than
this; for, as new forms are produced, unless we admit that
specific forms can go
on indefinitely increasing in number, many old forms must
become extinct. That
the number of specific forms has not indefinitely increased,
geology plainly
tells us; and we shall presently attempt to show why it is that
the number of
species throughout the world has not become immeasurably
great. We have seen that the species which are most numerous
in individuals have
the best chance of producing favourable variations within
any given period. We
have evidence of this, in the facts stated in the second
chapter showing that it
is the common and diffused or dominant species which offer
the greatest number
of recorded varieties. Hence, rare species will be less quickly
modified or
improved within any given period; they will consequently be
beaten in the race
for life by the modified and improved descendants of the
commoner species. From these several considerations I think it
inevit
文档评论(0)