50 Cells and Temperature
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 37 ℃; 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 homeotherms, and those whose body temperature varies with their environment, 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 a change in the chill of the deep water, and their body temperatures remain constant.
Child safety lock 儿童锁
Toxic capsule 问题胶囊
黄岩岛对峙“僵局”
Pump Pain Index 加油痛苦指数
“站队”英文怎么说
概念车 concept car
网络钟点工 virtual troubleshooter
Conception and Governor vessels 任督二脉
Boutique hotel 精品酒店
Fall guy 顶包者
Chronological age 实际年龄
The Hottest Ethnic Trend 最炫民族风
禁狗令 dog ban
Mine flood 煤矿透水
道德银行 morality bank
关注“赤脚医生”
“中医”走向世界
老酸奶遭遇“明胶”风波
星巴克“昆虫着色剂”
通胀挂钩债券 inflation-linked bond
页岩气 shale gas
Transit of Venus 金星凌日
油价上“涨”
设立“学术欺诈罪”
“舌尖上的中国2”美食英文说法抢鲜看之七(组图)[1]
继续推进“社会公平正义”
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转基因食品 GM food
韩“化学阉割”恋童癖
Subway fire brigade 地铁消防队
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