Question 2 – 4:
While the most abundant and dominant species within a particular ecosystem 1
is often crucial in perpetuating the ecosystem, a “keystone” species, here defined 2
as one whose effects are much larger than would be predicted from its appearance, 3
also play a vital role. But because complex species interactions may be involved, 4
identifying a keystone species by removing the species and observing changes in 5
the ecosystem is problematic. 6
It might seem that certain traits would clearly define a species as a keystone 7
species; for example, Pisaster ochraceus is often a keystone predator because it 8
consumes and suppresses mussel populations, which in the absence of this starfish 9
can be a dominant species. But such predation on a dominant or potentially dominant 10
species occurs in systems that do as well as in systems that do not have species that 11
play keystone roles. Moreover, whereas P. ochraceus occupies an unambiguous 12
keystone role on wave-exposed rocky headlands, in more wave-sheltered habitats 13
the impact of P. ochraceus predation is weak or nonexistent, and at certain sites sand 14
burial is responsible for eliminating mussels. Keystone status appears to depend on 15
context, whether of particular geography or of such factors as community diversity 16
(for example, a reduction in species diversity may thrust more of the remaining species 17
into keystone roles) and length of species interaction (since newly arrived species 18
in particular may dramatically affect ecosystem). 19
Question 2:
The primary purpose of the passage is to
A. point out some of the differences between dominant and keystone species
B. emphasize the complexity of the interactions that occur between two particular species
C. detail the effect of a particular habitat on the role occupied by a certain keystone species
D. illustrate the importance of community diversity for the perpetuation of an ecosystem
E. explain some considerations involved in determining whether a species occupies a keystone role
The key is D! But I choose E.
Help!!!
the first paragraph introduces the definition of "key stone", then the first sentence of second paragraph states the TS of the passage: It might seem that certain traits would clearly define a species as a keystone species. Giving the example of P, second P describes some detailed factors. Finally the passage summarizes all factor that Keystone status appears to depend on .
So the answer D is right.
唉，还是不懂！
sorry,I made a mistake.I will replay your Q later.
hehe
agree!
Further Help Needed!!
呵呵
我也说不至于这么荒谬
顶一下，这篇阅读有没有标准的答案？？
楼上的问题我也有同感？第四题为什么是c??而不是D?
顶！！！查了一下这篇3个答案好乱呀！到底应该是什么呀？EBD or DBC?
还有想请教一句话的意思，看了半天也不明白，尤其是黄色的部分，谁是这句的主语啊？
请哪位帮忙看一下？谢谢了。
It might seem that certain traits would clearly define a species as a keystone species; for example, Pisaster ochraceus is often a keystone predator because it consumes and suppresses mussel populations, which in the absence of this starfish can be a dominant species.
I vote for EBD.
It might seem that certain traits would clearly define a species as a keystone species; for example, Pisaster ochraceus is often a keystone predator because it consumes and suppresses mussel populations, which in the absence of this starfish can be a dominant species.
帮MM翻译这句话啊：有某些特性能够清晰的确定一个物种为keystone物种。比如说，Pisaster ochraceus 经常是keystone物种的捕食者，因为PO食用贝类，抑制贝类的生长，而这些贝类在这种海星(PO)不出现的时候是一个dominant物种。
which指的是mussel populations，this starfish指的是Pisaster ochraceus .
贴出来了，麻烦Tony nn 帮忙看一下，谢谢。
Question 2: The primary purpose of the passage is to
A. point out some of the differences between dominant and keystone species
B. emphasize the complexity of the interactions that occur between two particular species
C. detail the effect of a particular habitat on the role occupied by a certain keystonspecies
D. illustrate the importance of community diversity for the perpetuation of an ecosystem
E. explain some considerations involved in determining whether a species occupies a keystone role
Question 3:
Which of the following, if true, would most clearly support the argument about keystone
status advanced in the last sentence of the passage (lines 15 – 19)?
A. A species of bat is primarily responsible for keeping insect populations within an
ecosystem low, and the size of the insect population in turn affects bird species
within that ecosystem.
B. A species of iguana occupies a keystone role on certain tropical islands, but does
not play that role on adjacent tropical islands that are inhabited by a greater number
of animal species.
C. Close observation of a savannah ecosystem reveals that more species occupy
keystone roles within that ecosystem than biologists had previously believed.
D. As a keystone species of bee becomes more abundant, it has a larger effect on
the ecosystem it habits.
E. A species of mouse that occupies a keystone role in a prairie habitat develops
coloration patterns that camouflage it from potential predators.
Question 4:
The passage suggests which of the following about the identification of a species as
a keystone species?
A. Such an identification depends primarily on the species’ relationship to the dominant species.
B. Such an identification can best be made by removing the species from a particular
ecosystem and observing changes that occur in the ecosystem.
C. Such an identification is likely to be less reliable as an ecosystem becomes less diverse.
D. Such an identification seems to depend on various factors within the ecosystem.
E. Such an identification can best be made by observing predation behavior.
I vote for EBD.
It might seem that certain traits would clearly define a species as a keystone species; for example, Pisaster ochraceus is often a keystone predator because it consumes and suppresses mussel populations, which in the absence of this starfish can be a dominant species.
帮MM翻译这句话啊：有某些特性能够清晰的确定一个物种为keystone物种。比如说，Pisaster ochraceus 经常是keystone物种的捕食者，因为PO食用贝类，抑制贝类的生长，而这些贝类在这种海星(PO)不出现的时候是一个dominant物种。
which指的是mussel populations，this starfish指的是Pisaster ochraceus .
谢谢而今迈步从头越mm的翻译哦，看懂了。估计上午是脑子灌水了，怎么会没看懂涅？郁闷啊！还有十来天就要考的人了。。。
严重同意而今迈步从头越班主的最后选项 EBD，其他答案完全不合理。
只是疑惑为何这片阅读的讨论不在讨论汇总中列出，吓我一身冷汗！寒！
建议斑竹补充到汇总中。 谢了！
agree E B D
还是觉得GWD2-4答案选C。“The passage suggests which of the following about the identification of a species as a keystone species?”，从这句“(for example, a reduction in species diversity may thrust more of the remaining species into keystone roles)，支持了C的说法：Such an identification is likely to be less reliable as an ecosystem becomes less diverse.
欢迎继续讨论。
对于第2题，支持E。全文应该是贯穿这一主题的。
C选项是说，“对于特定栖息地点之于'keystone'物种功能的影响，进行详细地阐述。”此选项应该不是文中的主线，仅仅是一种细节论述。
EBD, 恩!
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