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今天早上做了四篇OG阅读，其中有一篇错的比较多。先发出来请NN分析一下。
It was once assumed that all living things could be
divided into two fundamental and exhaustive categories.
Multicellular plants and animals, as well as many unicellu-
lar organisms, are eukaryotic—their large, complex cells
(5) have a well-formed nucles and many organelles. On the
other hand, the true bacteria are prokaryotic cell, which
are simple and lack a nucleus. The distinction between
eukaryotes and bacteria, initially defined in terms of
subcellular structures visible with a microscope, was ulti-
(10) mately carried to the molecular level. Here prokaryotic and
eukaryotic cells have many features in common. For
instance, they translate genetic information into proteins
according to the same type of genetic coding. But even
where the molecular processes are the same, the details in
(15) the two forms are different and characteristic of the respec-
tive forms. For example, the amino acid sequences of vari-
ous enzymes tend to be typically prokaryotic or eukaryotic.
The differences between the groups and the similarities
within each group made it seem certain to most biologists
(20) that the tree of life had only two stems. Moreover, argu-
ments pointing out the extent of both structural and func-
tional differences between eukaryotes and true bacteria
convinced many biologists that the precursors of the
eukaryotes must have diverged from the common
(25)ancestor before the bacteria arose.
Although much of this picture has been sustained by
more recent research, it seems fundamentally wrong in one
respect. Among the bacteria, there are organisms that are
significantly different both from the cells of eukaryotes and
(30)from the true bacteria, and it now appears that there are
three stems in the tree of life. New techniques for deter-
mining the molecular sequence of the RNA of organisms
have produced evolutionary information about the degree
to which organisms are related, the time since they diverged
(35) from a common ancestor, and the reconstruction of ances-
tral versions of genes. These techniques have strongly
suggested that although the true bacteria indeed form a
large coherent group, certain other bacteria, the archaebac-
teria, which are also prokaryotes and which resemble true
(40) bacteria, represent a distinct evolutionary branch that
far antedates the common ancestor of all true bacteria.
175. The passage is primarily concerned with
(A) detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
(B) outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
(C) evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected.
(D) summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes (B)
(E) formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes
176 According to the passage, investigations of eukaryotic and prokaryotic cells at the molecular level supported the conclusion that
(A) most eukaryotic organisms are unicellular
(B) complex cells have well-formed nuclei
(C) prokaryotes and cukaryotes form two fundamental categories
(D) subcellular structures are visible with a microscope (C)
(E) prokaryotic and eukaryotic cells have similar enzymes
177. According to the passage, which of the following statements about the two-category hypothesis is likely to be true?
(A) It is promising because it explains the presence of true bacteria-like organisms such as organelles in eukaryotic cells.
(B) It is promising because it explains why eukaryotic cells, unlike prokaryotic cells, tend to form multicellular organisms.
(C) It is flawed because it fails to account for the great variety among eukaryotic organisms.
(D) It is flawed because it fails to account for the similarity between prokaryotes and eukaryotes. (E)
(E) It is flawed because it fails to recognize an important distinction among prokaryotes.
178. It can be inferred from the passage that which of the following have recently been compared in order to clarify the fundamental classifications of living things?
(A) The genetic coding in true bacteria and that in other prokaryotes
(B) The organelle structures of archaebacteria, true bacteria, and eukaryotes
(C) The cellular structures of multicellular organisms and unicellular organisms
(D) The molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA (D)
(E) The amino acid sequences in enzymes of various eukaryotic species and those of enzymes in archaebecterial species
178.
This question requires you to identify information implied rather than stated in the passage. D, the
best answer, can be inferred from lines 30-31, which state that it “now appears that there are three
stems in the tree of life”-that is, three categories of organism-because “new techniques for
determining the molecular sequence of the RNA of organisms have produced evolutionary
information…” From this it can be inferred, as D states, that researchers compared the molecular
sequences in the RNA of each kind of organism postulated by the new view-eukaryotic, bacteria,
and archaebateria. The other choices cannot be inferred from the passage; each describes types of
features discussed in the context of earlier, not later, research.
179. If the “new techniques” mentioned in line 31 were applied in studies of biological classifications other than bacteria, which of the following is most likely?
(A) Some of those classifications will have to be reevaluated.
(B) Many species of bacteria will be reclassified
(C) It will be determined that there are four main categories of living things rather than three.
(D) It will be found that true bacteria are much older than eukaryotes. (A)
(E) It will be found that there is a common ancestor of the eukaryotes, archaebacteria, and true bacteria.
180. According to the passage, researchers working under the two-category hypothesis were correct in thinking that
(A) prokaryotes form a coherent group
(B) the common ancestor of all living things had complex properties
(C) eukaryotes are fundamentally different from true bacteria
(D) true bacteria are just as complex as eukaryotes (C)
(E) ancestral versions of eukaryotic genes functioned differently from their modern counterparts.
181. All of the following statements are supported by the passage EXCEPT:
(A) True bacteria form a distinct evolutionary group.
(B) Archaebacteria are prokaryotes that resemble true bacteria.
(C) True bacteria and eukaryotes employ similar types of genetic coding.
(D) True bacteria and eukaryotes are distinguishable at the subcellular level. (E)
(E) Amino acid sequences of enzymes are uniform for eukaryotic and prokaryotic organisms.
182. The author’s attitude toward the view that living things are divided into three categories is best described as one of
(A) tentative acceptance
(B) mild skepticism
(C) limited denial
(D) studious oriticism (A)
(E) whole hearted endorsement
175.
The best answer is B. The first paragraph reviews inquires leading to the hypothesis that two
categories of organism exist; the second explains how “more recent research” (line 27) supports a
three-category hypothesis. Thus, the passage is primarily concerned with outlying factors
contributing to the current hypothesis about the number of such categories. Choice A is wrong
because the passage describes the replacement of a dichotomous with a dichotomous model, not
the reverse. C is wrong because the passage mentions no experimental proof that the prokaryotes
were older than expected; D is wrong because the passage only briefly discusses the structure and
function of eukaryotes and prokaryotes, never mentioning those of archaebateria. E is wrong
because the passage mentions no particular “mechanisms of evolution” that created the ancestors
of the prokaryotes.
176.
The best answer is C. In lines 10-20, the passage states that, although molecular investigation
revealed some similarities between prokaryotic and eukaryotic cells, “the differences between the
groups and the similarities within each group made it seem certain to most biologists that the tree
of life had only two stems” (lines 18-20)-that is, “two fundamental categories,” as C asserts. The
passage does not address what proportion of eukaryotic organisms are unicellular (choice A) or
whether all complex cells have well-formed nuclei (choice B). That “sub cellular structures are
visible with a microscope” (choice D) is described as established “initially”-that is, before the
research was “ultimately carried to the molecular level” (lines 7-10). According to the passage,
molecular investigation supports the idea that “sequences of …enzymes tend to be typically
prokaryotic or eukaryotic”-not that those enzymes are similar (lines 16-17), as E claims.
177.
The best answer is E. According to the passage, the two-category hypothesis, which assumed “that
all living things could be divided into two…categories,” (lines 1-2) now “seems fundamentally
wrong” (line 27) because it does not account for evidence that two kinds of prokaryotic organisms
exist: true bacteria and “a distinct evolutionary branch,” archaebateria (line 40). Thus, the
hypothesis is said to ignore an important distinction among prokaryotes, as E states. Choice A is
wrong because the passage does not even mention bacteria alike organisms existing within
eukaryotic cells. B contradict the passage, which states that “many unicellular organisms… are
eukaryotic.” C and D are wrong because each identifies as a flaw the failure to “account for”
conditions that the passage indicates the hypothesis accounted for.
178.
This question requires you to identify information implied rather than stated in the passage. D, the
best answer, can be inferred from lines 30-31, which state that it “now appears that there are three
stems in the tree of life”-that is, three categories of organism-because “new techniques for
determining the molecular sequence of the RNA of organisms have produced evolutionary
information…” From this it can be inferred, as D states, that researchers compared the molecular
sequences in the RNA of each kind of organism postulated by the new view-eukaryotic, bacteria,
and archaebateria. The other choices cannot be inferred from the passage; each describes types of
features discussed in the context of earlier, not later, research.
179.
The best answer is A. This question requires you to select the answer that, based on information
presented in the passage, describes the most likely result of applying the “new techniques” (lines
31) to biological classifications other than bacteria. Lines 31-36 state that these techniques
“produced…information about the degree to which organisms are related.” Specifically, the
techniques “strongly suggested” that the prokaryotes category includes two distinct kinds of
organisms (lines 36-37). This information, which suggests a reevaluation of the prokaryote
classification, provides support for the statement that “classification other than bacteria’ are also
likely to require reevaluation if the same techniques are used to study them, as A states.
180.
The best answer is C. Lines 26-28 indicate that C is an aspect of the two-category hypothesis that
“has been sustained by more recent research.” Thus, the passage supports the assumption, made
by proponents of the two-category hypothesis, that “eukaryotes are fundamentally different from
true bacteria” (choice C). The passage contradicts the idea that prokaryotes “from a coherent
group” (choice A) because it states that there is “one respect” (line 27-28) in which new evidence
contradicts the hypothesis: in addition to the eukaryotes and the “true bacteria,” which are
prokaryotes, there exists another distinct “evolutionary branch” within the prokaryotes: the
archebateria (38-41). The two-category hypothesis, as presented in the passage, proposes neither B
nor E and asserts the opposite of D.
181.
The best answer is E, the only choice NOT supported by the passage. Lines 37-38 support the idea
that “true bacteria indeed form a large coherent group” of the kind postulated by the two-category
hypothesis-that, that they are a “distinct evolutionary group” (choice A). Lines 38-40 assert that
“archaebateria…are prokaryotes and …resemble true bacteria,” as B states. Lines 10-13 support C:
“prokaryotic and eukaryotic cells.. translate genetic information… according to the same type of
genetic coding.” D is supported by lines 7-10 in the passage, which state that “the distinction
between eukaryotes and bacteria” was “initially defined in terms of subcellular structures visible
with a microscope.” E, however, is contradicted by lines 25-27: “the amino acid sequences of
various enzymes tend to be typically prokaryotic or eukaryotic.”
182.
The best answer is A, which aptly describes the author’s attitude toward the hypothesis that there
are three categories of living things. In lines 30-31 the author states that “it now appears that there
are three stems in the tree of life” because new techniques “have strongly suggested” the accuracy
of the three-category view (lines 31-41). That the author accepts the three-category hypothesis is
suggested by this mention of “strong” support. That this acceptance is “cautious” is conveyed by
the use of the terms “seems” (lines 27), “appears,” and “suggested.” Such caution rules out the
“wholehearted endorsement” described by E; nor does the author express “denial” of (choice C),
“criticism” about 9choice D), or “skepticism” about (choice B) the three-category hypothesis.
通过这篇文章的分析我觉得生物类段落、天文学以及其他内容不熟悉的文章考试时要做笔记，因为文章内容不熟悉，生词多，并且文章中有许多分类，分类之间异同点的比较。单凭看就把这些内容记住简直不可能。做笔记时要记好各种分类，每一类的性质特点。 | 
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发表于 2005-7-8 15:28:00
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