编辑点评: 研习GRE作文考试的优秀范文不仅可以学到有用的词汇和句子,更能从中学习逻辑的构建方式和作文框架的结构等内容,这里为大家提供GRE的范文,希望对同学们的备考有所帮助。
Cells cannot remain alive outside certain limits of temperature and much narrower limits mark the boundaries of effective functioning. Enzyme systems of mammals and birds are most efficient only within a narrow range around 37C;a departure of a few degrees from this value seriously impairs their functioning. Even though cells can survive wider fluctuations the integrated actions of bodily systems are impaired. Other animals have a wider tolerance for changes of bodily temperature.
For centuries it has been recognized that mammals and birds differ from other animals in the way they regulate body temperature. Ways of characterizing the difference have become more accurate and meaningful over time, but popular terminology still reflects the old division into warm-blooded and cold-blooded species; warm-blooded included mammals and birds whereas all other creatures were considered cold- blooded.
As more species were studied, it became evident that this classification was inadequate. A fence lizard or a desert iguana-each cold-blooded----usually has a body temperature only a degree or two below that of humans and so is not cold. Therefore the next distinction was made between animals that maintain a constant body temperature, called home0therms, and those whose body temperature varies with their environments, called poikilotherms. But this classification also proved inadequate, because among mammals there are many that vary their body temperatures during hibernation.
Furthermore, many invertebrates that live in the depths of the ocean never experience change in the depths of the ocean never experience change in the chill of the deep water, and their body temperatures remain constant.
2016届高考英语二轮复习综合练:考点考向考法18
2016届高考英语二轮高频词汇练习5
2016届高考英语二轮复习综合练:考点考向考法19
2016届高考英语二轮复习综合练:考点考向考法22
2016届高考英语二轮高频词汇练习6
2016届高考英语二轮题型专题方略课件:专题4 语法填空和短文改错 第3讲 语法专题 10 特殊句式(通用版)
2016届高考英语二轮高频词汇练习7
2016届高考英语二轮高频词汇练习2
2016届高考英语二轮复习课堂达标训练:第1部分 题型专题方略 专题4 第1讲 语法填空题型分析(通用版)
2016届高考英语二轮题型专题方略课件:专题4 语法填空和短文改错 第3讲 语法专题 6 情态动词(通用版)
2016届高考英语二轮高频词汇练习14
2016届高考英语二轮题型专题方略课件:专题2 完形填空(通用版)
2016届高考英语二轮语法复习课件:专题10 特殊句式(人教版)
2016届高考英语二轮高频词汇练习15
2016届高考英语二轮复习综合练:考点考向考法21
2016届高考英语二轮题型专题方略课件:专题4 语法填空和短文改错 第3讲 语法专题 4 动词的时态、语态和语气(通用版)
2016届高考英语二轮题型专题方略课件:专题3 书面表达(通用版)
2016届高考英语二轮高频词汇练习10
2016届高考英语二轮题型专题方略课件:专题4 语法填空和短文改错 第3讲 语法专题 2代词和介词(通用版)
2016届高考英语二轮复习课堂达标训练:第1部分 题型专题方略 专题1 第5讲 篇章结构题(通用版)
2016届高考英语二轮高频词汇练习3
2016届高考英语二轮题型专题方略课件:专题4 语法填空和短文改错 第3讲 语法专题 3 形容词和副词(通用版)
2016届高考英语二轮高频词汇练习12
2016届高考英语二轮高频词汇练习11
2016届高考英语二轮复习综合练:考点考向考法25
2016届高考英语二轮高频词汇练习9
2016届高考英语二轮复习针对训练:专题1 阅读理解 第4讲 主旨大意题(通用版)
2016届高考英语二轮题型专题方略课件:专题1 阅读理解 第5讲 篇章结构题(通用版)
2016届高考英语二轮题型专题方略课件:专题1 阅读理解 第3讲 词义猜测题(通用版)
2016届高考英语二轮题型专题方略课件:专题1 阅读理解 第4讲 主旨大意题(通用版)