grossweight生物专业英语蒋悟生编-翻译

2021年1月20日发(作者：鲆科)
生物工程专业英语

The Origin of Species
Biologists Define a Species
Modern biology generally define a species as group of actuall
y or potentially interbreeding populationsthat is reproductivel
y isolated from the such groups. Members of a species can in
terbreed with each other,but they cannot breed with organis
ms belonging to another species. One advantage of the stan
dard ofreproductive isolation is that it is very precise. Notice,
however, that it can only be applied to organismsthat reprod
uce sexually. Asexual reproducers, including most prokaryote
s, many plants, and someanimals, must be classified into spec
ies on the basis of physical (biochemical or morphological) tr
aits.
现代生物学大体将物种定义为实际上的一群或潜在的杂交群体，
即从
这个群体隔离繁殖的后代。种族中个体可以互相交配，但种间不能。
这种繁殖隔离的一个优 势是很精确。
但仅适用于性繁殖的生物。
非性
繁殖，包括大多数原核生物，许多植物， 某些动物，需要通过自然特
征进行归类。


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生物工程专业英语

ting Gene Exchange
Two general types of mechanisms operate to block the excha
nge of genes between individuals of relatedgroups. The first
general type is made up of prezygotic isolating mechanisms t
hat prevent the formation ofzygotes. Prezygotic isolation fall
s into two categories: ecological and behavioral. In the first c
ase, tworelated group may become adapted to slightly differe
nt environments-perhaps varying soil types or foodsources.
Over time, these genetic differences become so great that su
ccessful cross-fertilization can nolonger take place. In behavi
oral isolation, related groups evolve differing behaviors such
as specificmating rituals-that restrict the exchange of genes t
o members of the same group.
两种基 因型机制阻碍了相关群体中个体的基因交换。
第一种基因型由
前合子机械隔离机制阻止合子的生 成。
前合子隔离分两类：
生态学的
和行为学的。
第一种情况，
两个相 关群体可能分别适应稍微不同的环
境，如土壤类型或食物来源的变化。长时间，这些遗传差异变得很大< br>而很难异体受精。
而行为学隔离，
相关的群组进化成不同的行为方式，
例如，结 婚仪式，从而限制了同群成员基因交流。


2
生物工程专业英语

Sometimes the differences that produce prezygotic isolation i
nvolve mechanical isolation. That is,mating is physically impo
ssible between members of different species because genitals
of males andfemales are structurally incompatible or because
molecules on the surfaces of sperm and egg fail to bind.A fin
al type of prezygotic mechanism is temporal isolation, in whic
h time-related environmental cues thattrigger reproductive pr
ocesses are different for related species. < br>有时，产生前合子隔离的差异涉及了隔离机制。即，由于生殖器结构
不匹配或精卵分子表面不结合 而使不同种群成员间不能自然结合。
最
后一类前合子机制是暂时隔离，
与时间有关的环 境因素触发了相关物
种的不同繁殖过程。

In postzygotic isolating mechanisms mating occur, but the re
sulting hybrid organism is inviable orsterile. In a special case
of hybrid sterility termed hybrid breakdown, the second and s
ubsequentgenerations after a cross show reduced reproducti
ve success. Contrast this fact with the very differentoutcome
of crossbreeding between two genetically distant members of

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生物工程专业英语

the same species, where the result isoften heterozygote adva
ntage (hybrid vigor).
在合子 后隔离机制中，匹配可以进行，但或不产生杂种或杂种不育。
杂种不育在某些特殊情况下，
是指 第二代或以后几代显示出杂交繁殖
能力的降低。
正是同种远基因成员间的杂交产生不同的结果，
而产生
杂种优势。

Populations of a species that are spread out over a broad geo
graphical range are often arrayed in a cline-a gradual change
in one or more characteristics as each population evolves ada
ptations to its own localenvironment. Along a cline, subspeci
es with distinct characteristics may arise. Often, individuals at
eitherend of a cline are reproductively isolated.

地域上分布很广的种的群体中，经 常存在变异群，因为适应当地的
环境，每个群体逐渐产生一个或多个与众不同的特点。在变异群中，带有明显特征的亚群可能产生。
通常，
在两个变异群中的个体是繁殖
隔离的。
ng a Species: How Gene Pools Become Isolated
Ernst Mayr's model of allopatric speciation proposes that spe
cies can originate in a two-stage the first stage, po

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生物工程专业英语

pulations of existing species are separated by a physical or ge
ographical barrier. As aresult, over time genetic differences le
ading to pre- or postzygotic isolation arise between the two
the second stage, the diverged populations may ag
ain come into contact. If this happens, speciationbecomes co
mplete through the action of natural selection.
Lesson Nine
The Origin of Species
Biologists Define a Species
Modern biology generally define a species as group of actuall
y or potentially interbreeding populationsthat is reproductivel
y isolated from the such groups. Members of a species can in
terbreed with each other,but they cannot breed with organis
ms belonging to another species. One advantage of the stan
dard ofreproductive isolation is that it is very precise. Notice,
however, that it can only be applied to organismsthat reprod
uce sexually. Asexual reproducers, including most prokaryote
s, many plants, and someanimals, must be classified into spec
ies on the basis of physical (biochemical or morphological) tr

5
生物工程专业英语

aits.
现代生物学大体将物种定义 为实际上的一群或潜在的杂交群
体，即从这个群体隔离繁殖的后代。种族中个体可以互相交配，但种间不能。
这种繁殖隔离的一个优势是很精确。
但仅适用于性繁殖的生
物。非性繁殖 ，包括大多数原核生物，许多植物，某些动物，需要通
过自然特征进行归类。
ting Gene Exchange
Two general types of mechanisms operate to block the excha
nge of genes between individuals of relatedgroups. The first
general type is made up of prezygotic isolating mechanisms t
hat prevent the formation ofzygotes. Prezygotic isolation fall
s into two categories: ecological and behavioral. In the first c
ase, tworelated group may become adapted to slightly differe
nt environments-perhaps varying soil types or foodsources.
Over time, these genetic differences become so great that su
ccessful cross-fertilization can nolonger take place. In behavi
oral isolation, related groups evolve differing behaviors such
as specificmating rituals-that restrict the exchange of genes t
o members of the same group.
两种基因型机制阻碍了相关群体中个体的基 因交换。
第一种基因型由
前合子机械隔离机制阻止合子的生成。
前合子隔离分两类：< br>生态学的

6
生物工程专业英语

和行为学的。
第 一种情况，
两个相关群体可能分别适应稍微不同的环
境，如土壤类型或食物来源的变化。长时间 ，这些遗传差异变得很大
而很难异体受精。
而行为学隔离，
相关的群组进化成不同的行 为方式，
例如，结婚仪式，从而限制了同群成员基因交流。

Sometimes the differences that produce prezygotic isolation i
nvolve mechanical isolation. That is,
28









Lesson One
mating is physically impossible between members of different
species because genitals of males andfemales are structurally

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生物工程专业英语

incompatible or because molecules on the surfaces of sperm
and egg fail to bind.A final type of prezygotic mechanism is t
emporal isolation, in which time-related environmental cues t
hattrigger reproductive processes are different for related spe
cies.
有时，产生前合子隔离的差异涉及了隔离机制。即，由于生殖器结构
不匹配或精卵分子表面不结合而使不同种群成员间不能自然结合。
最
后一类前合子机制是暂时 隔离，
与时间有关的环境因素触发了相关物
种的不同繁殖过程。

In postzygotic isolating mechanisms mating occur, but the re
sulting hybrid organism is inviable orsterile. In a special case
of hybrid sterility termed hybrid breakdown, the second and s
ubsequentgenerations after a cross show reduced reproducti
ve success. Contrast this fact with the very differentoutcome
of crossbreeding between two genetically distant members of
the same species, where the result isoften heterozygote adva
ntage (hybrid vigor).
在合子后隔离机制中，匹配可以进行，但或不产生杂种或杂种不育。
杂种不育在某些特殊情况下 ，
是指第二代或以后几代显示出杂交繁殖

8
生物工程专业英语

能力的降低。
正是同种远基因成员间的杂交产生不同的结果，
而产生
杂种优势 。

Populations of a species that are spread out over a broad geo
graphical range are often arrayed in a cline-a gradual change
in one or more characteristics as each population evolves ada
ptations to its own localenvironment. Along a cline, subspeci
es with distinct characteristics may arise. Often, individuals at
eitherend of a cline are reproductively isolated.

地域上分布很广的种的群体中，经常存在变异群，因为适应当地的< br>环境，每个群体逐渐产生一个或多个与众不同的特点。在变异群中，
带有明显特征的亚群可能产生 。
通常，
在两个变异群中的个体是繁殖
隔离的。

ng a Species: How Gene Pools Become Isolated
Ernst Mayr's model of allopatric speciation proposes that spe
cies can originate in a two-stage the first stage, po
pulations of existing species are separated by a physical or ge
ographical barrier. As aresult, over time genetic differences le
ading to pre- or postzygotic isolation arise between the two
the second stage, the diverged populations may ag

9
生物工程专业英语

ain come into contact. If this happens, speciationbecomes co
mplete through the action of natural selection
异地物种形成 模
型认为，物种可能起源于两个阶段。第一阶段，已经存在的物种群体
可能由于自然或地理屏障 被隔离。结果，长时间后，在两个群体间遗
传差异导致前合子或后合子隔离的产生。

Lesson One
第二阶段，
这些趋异群体可能再次接触，
物种发生可 能通过自然选择
发生。
Genetic Bases of speciation
The extent of differences between populations that are diverg
ing into separate species or betweenspecies that have already
diverged is represented by a statistic called genetic identity-t
he relativeproportion of the same structural genes present in
members of groups being compared. In general,biologists be
lieve that the genetic events leading to speciation take place
gradually. Once a new specieshas arisen, it tends to diverge
genetically from related species at a more rapid pace. In som
e cases, such asthe primate order, major differences in body f
orm are not reflected by corresponding divergences instructu
ral genes. This has led Biologists to hypothesize that small ch

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生物工程专业英语

anges in regulatory genes mayaccount for many of the large-
scale changes responsible for sepciation and the origin of hig
her taxonomicgroups.
能够趋异的群体或已经趋异的物种，
他们之间差异的扩大，
由一个稳
定的遗传识别代表 。
即在可比群体成员中相同基因所占相关比例。
大
体而言，生物学家相信，遗传导致的 物种形成是逐渐发生的。在某些
情况下，
身体主要差别并不能反映结构基因的趋异，
生 物学家因此提
出，
调控基因很少的改变可能导致很大规模物种改变和更高分类学上
群体 的产生。

One mechanism that may rapidly split populations genetically
is polyploidization
—
the suddenmultiplication of an entire co
mplement of chromosomes. This can result in sympatric spec
iation, in whichnew species arise even though no geographic
al isolation has taken place. A phenomenon similar topolyplo
idization involving the rearrangement of chromosomes has b
een proposed to explain theevolutionary origin of giant pand
as. Clearly, species can originate in a variety of ways.

遗传学上可以快速 分离群体的一个机制是多倍体，一个完全互补染
色体组的突然倍增。
结果导致同域物种形成，< br>即使没有地理隔离也会

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