TT GWD11-24-27

xiaobenzhu

Q24 to Q27:

      Anole lizard species that

            occur together (sympatrically)

            on certain Caribbean islands

Line     occupy different habitats:

  (5)      some live only in the grass,

some only on tree trunks, and

some only on twigs.  These

species also differ morpho-

logically:  grass dwellers are

 (10)     slender with long tails, tree

dwellers are stocky with long

legs, twig dwellers are slender

but stubby-legged.  What is

striking about these lizards

 (15)     is not that coexisting species

differ in morphology and habi-

tat use (such differences are

common among closely related

sympatric species), but that

 (20)     the same three types of habi-

            tat specialists occur on each

            of four islands:  Puerto Rico,

Cuba, Hispaniola, and Jamaica.

Moreover, the Puerto Rican

 (25)     twig species closely resembles

the twig species of Cuba,

Hispaniola, and Jamaica in

morphology, habitat use, and

behavior.  Likewise, the spe-

 (30)     cialists for other habitats are

similar across the islands.

      The presence of similar

            species on different islands

could be variously explained.

 (35)
                   An ancestral species might

have adapted to exploit a

particular ecological niche on

one island and then traveled

           over water to colonize other

 (40)    islands.  Or this ancestral

species might have evolved

at a time when the islands

were connected, which some

of these islands may once

 (45)     have been.  After the islands

separated, the isolated lizard

populations would have become

distinct species while also

retaining their ancestors’ niche

 (50)     adaptations.  Both of these

scenarios imply that speciali-

zation to each niche occurred

only once.  Alternatively, each

specialist could have arisen

 (55)     independently on each of the

islands.

      If each type of specialist

evolved just once, then similar

specialists on different islands

 (60)     would be closely related.

Conversely, if the specialists

evolved independently on each

island, then a specialist on one

island would be more closely

 (65)     related to other types of anoles

on the same island—regardless

of their ecological niches—

than it would be to a similar

specialist on a different island.

 (70)           Biologists can infer how

species are related evolu-

tionarily by comparing DNA

sequences for the same genes

in different species.  Species

 (75)     with similar DNA sequences

for these genes are generally

more closely related to each

other than to species with less-

similar DNA sequences.  DNA

(80)         evidence concerning the anoles

led researchers to conclude

that habitat specialists on one

island are not closely related

to the same habitat specialists

(85)         elsewhere, indicating that spe-

cialists evolved independently

on each island.

--------------------------------------------------------------------------------

Q24:   

The primary purpose of the passage is to

                       

1. describe some unusual features of anole lizard species
2. account for a particular type of behavior found among anole lizard species
3. contrast two types of evidence that have been used to support a particular hypothesis concerning anole lizard species
4. explain how researchers resolved a particular scientific question concerning anole lizard species
5. examine different explanations for a particular trait common to certain anole lizard species

The answer is D, but I chose B. I think only last Paragraph is related to the how researches resolved sth. about lizard species. So D is narrowed.

Can any NN explane?

Thanks.

ll_422

B中的BEHAVIOR明显不对,  文中未提及, 所以选D

leepee

以下是引用ll_422在2006-11-23 21:02:00的发言：
B中的BEHAVIOR明显不对,  文中未提及, 所以选D

agee,but why is E wrong?

chamcham

E: examine different explanations for a particular trait common to certain anole lizard species

The explainations are for a set of traits rather than a particular trait. It is very tricky since the first half looks perfect and I did wrong 2, damn GMAC

jiaojiao1426

36. The passage suggests that if a grass-dwelling anole lizard species evolved on one island and then traveled over water to colonize a second island, the grass-dwelling anoles on the two islands would eventually

 

A.      develop very different DNA sequences

B.       develop into different species that are more distantly related to each other than to tree- and twig-dwelling anoles on their own islands

C.      come to differ significantly from one another in habitat use

D.      develop into different, but closely related, species

E.       evolve significant morphological differences

ans:d

请问这道题目的原句在哪里？我是看到最后一段

 Biologists can infer how species are related evolutionarily by comparing DNA sequences for the same genes in different species. Species with similar DNA sequences for these genes are generally more closely related to each other than to species with less-similar DNA sequences. DNA evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialists elsewhere, indicating that specialists evolved independently on each island.

把D排除的。请问错在了哪里？

谢谢~~~

海贝520

jiaojiao1426 发表于 2009-4-20 16:38
36. The passage suggests that if a grass-dwelling anole lizard species evolved on one island and the ...

原文说的是DNA检测出来是分散在不同岛上各自进化。
题目中问的是if先由同一祖先进化好了，再游到不同岛上繁衍，那么繁衍出来的两物种会怎样。定位错了

定位这句：Biologists can infer how species are related evolutionarily by comparing DNA sequences for the same genes in different species. Species with similar DNA sequences for these genes are generally more closely related to each other than to species with less-similar DNA sequences.