關于細胞和溫度的英語作文

　　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.

【細胞和溫度的英語作文】相關文章：

《溫度和溫度計》教學教案（通用7篇）08-18

海水溫度和鹽度教學教案10-08

溫度優(yōu)秀作文03-02

母愛的溫度作文04-10

掌心的溫度作文06-06

愛的溫度作文05-23

親情的溫度作文01-21

手心的溫度作文11-10

關于溫度的作文06-10

細胞的教學教案10-08