发信人: puikwan()
整理人: fredrink(2001-06-17 11:17:15), 站内信件
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The first day I have told you something about the structure and functional organization.Then today I want to tell you something about the human organism,the characteristics of life.
As we well know that human are organism and have many characteristics in the common with other organisms.The most important common feature of all organisms is life.Essential characteristics of life are organization,metabolism,reponsivenese,growth and development,and reproduction.Now let me introduce one by one to you.
ORGANIZATION:Living things are highly organized.All livings are composed of cells or,in the case of viruses,must be contained within cells to perform living functions.Cellsin turn are composed of highky organized organells,which depend on the precise organization of large molecules.Disruption of this organized state can result in loss of functions and death.
METABOLISM:Metabolism is the ability to use energy to perform vital function such as growth,movement,and reproduction.Plant can capture energy from sun-light,and humans obtain energy from food.
RESPONSIVENESS:An organism is responsive if it can sense changes in the environment and make adjustments that help maintain its life.Responses include movement toward food or water and away from danger or poor environmental conditions.Organisms can also make adjustments that maintain their internal environment.For example,if body temperature increase in a hot environment,sweat glands produce sweat,which can lower body temperature back toward normal levels.
GROWTH AND DEVELOPMENT:Growth result from the ability of cells to increase in size or number,producing an overall enlargment of all or part of the organism.Development includes the changes an organism undergoes through time;it begins with fertilization and ends at death. The greatest developmental changes occur before birth,but many changs continue after birth,and some cotnre throughout life.Development usually involves growth,but it also involves differentiation and morphogenesis.Differentiation is changes in cell structure and function from generalized.For example,following fertilization,generalized cells specialize to become specific cell types,such as skin,bone,musle,or nerve cells.As the cells specialize,tissues and organs take shape
REPRODUCTION:Reproduction is the formation of new cells or new organisms.Without reproduction of cells,growth and development are not possible.Without reproduction of the organism,there is only extinction for the species.
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If anybody have any questions,please send e-mail to me.I don't translate the text into Chinese.Because I want to improve your and my ability of English.I also tell the medical student that if you have the dream to become a great doctor,you must master the English language.The internets give us too much good datums about medical science,but there are some bad one.If you want to take the datum you want,you must learn the English language.One word will kill a life.As a doctor,we leard more and do more. |
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