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It was tough for me. Can anyone explain the 5th one y it is e and not c ??
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It was tough for me. Can anyone explain the 5th one y it is e and not c ??

Hi BITTU1234

The assumption that the author criticizes, of course, is the long-standing belief that, as a rule, parasites eventually become harmless and drift into symbiosis; the basis of his criticism is the discovery of harmful (i.e., nonbenign) fungi late in the game, at a time when presumably the relationship should be turning symbiotic. To the author, this means that the reverse road—from symbiosis to parasitism—is actually every bit as possible. But if (E) is true, and the branches that have followed that “reverse road” actually die off quickly, then the movement from symbiosis to parasitism is likely to be just an aberration— and the conventional assumption is correct after all.

(C) The implications at the heart of paragraph 3 take place after the relevant DNA has been isolated, so the difficulty of obtaining the DNA has nothing to do with the findings. (C) also presents an irrelevant comparison among the various difficulties of DNA isolation.
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It's good to read the passage with an eye on main ideas and structure.

The first paragraph tells us what lichens are and what symbiosis is
Quote:
A lichen consists of a fungus living in symbiosis (i.e., a mutually beneficial relationship) with an alga.
and introduces a puzzle ('mystery')
Quote:
... evolutionary origins of lichen-forming fungi have been a mystery ...
The first para also tells us that the mystery has now been solved (partially at least) and tells us what scientists have now learned.
Quote:
BUT a new DNA study has revealed the relationship of lichen-forming fungi to several previously known branches of the fungus family tree. The study reveals that, far from being oddities, lichen-forming fungi are close relatives of such common fungi as ...
Para 2 gives reasons why fungi in general and lichen fungi in particular are hard to study.
Quote:
In general, fungi present complications for the researcher. Fungi are usually parasitic or symbiotic, and researchers are often unsure whether they are examining fungal DNA or that of the associated organism. But lichen-forming fungi are especially difficult to study. They have few distinguishing characteristics of shape or structure, and ...
Para 2 goes on to tell us a result of these difficulties: Scientists classified (note the past tense) lichen-forming fungi as a separate grouping of fungi
Quote:
As a result, lichen-forming fungi have long been difficult to classify definitively within the fungus family. By default they were thus considered a separate grouping of fungi with an unknown evolutionary origin.
The para then tells us how new tools have helped researchers
Quote:
BUT, using new analytical tools that allow them to isolate the DNA of fungi in parasitic or symbiotic relationships, researchers were able to establish the DNA sequence ...
Para 3, the final para, tells us an implication of the new study: an old belief has been weakened.
Quote:
... it provides evidence to help overturn the long-standing evolutionary assumption that parasitic interactions inevitably evolve over time to a greater benignity and eventually to symbiosis so that the parasites will not destroy their hosts.
Para 3 then explains how this belief was weakened by the new findings.
Quote:
Fungi both harmful and benign can now be found both early and late in fungus evolutionary history. Given the new layout of the fungus family tree resulting from the lichen study, it
appears that fungi can evolve toward mutualism and then just as easily turn back again toward parasitism.


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Can anyone provide an explanation for Q3?
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Can anyone provide an explanation for Q3?
This is the question
Quote:
3. Which one of the following most accurately describes the organization of the passage?
My earlier post (just before your question) explained how the passage is organised. We need to be clear about the main points and structure of the passage. The right answer will describe the organisation -- accurately, in the right sequence, with mentions of all important points.

Quote:
(A) explanation of the difficulty of classifying lichens; description of the DNA sequence of lichen-forming fungi; summary of the implications of this description
- The passage does not describe the DNA sequence of the fungi.
- This answer does not even mention the new research.

Quote:
(B) definition of lichens; discussion of new discoveries concerning lichens’ evolutionary history; application of these findings in support of an evolutionary theory
- The new findings do not 'support any evolutionary theory'.
- This answer does even not mention that lichens have been a mystery, does not mention the difficulties of studying lichens, does not mention that the new DNA study has helped with the mystery, and does not talk about how scientists have now revised some old assumptions.

Quote:
(C) definition of lichens; discussion of the difficulty in classifying their fungal components; resolution of this difficulty and implications of the resulting research
All good!

Quote:
(D) discussion of the symbiotic relationship that constitutes lichens; discussion of how new research can distinguish parasitic from symbiotic fungi; implications of this research
- The answer is full of tempting misleading language.
- For example, the passage mentions but does not really discuss the symbiotic relationship. The passage does not discuss 'how new research can distinguish symbiotic from parasitic fungi'.
- As in B, this answer does not mention the most important points about the passage: why lichens have been a mystery and how the new study has helped to partially resolve the mystery.

Quote:
(E) explanation of the symbiotic nature of lichens; discussion of the problems this poses for genetic researchers; delineation of the implications these problems have for evolutionary theory
- This answer does not even mention the new research.

C is the clear answer.

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5. Which one of the following, if true, most weakens the author’s criticism of the assumption that parasitic interactions generally evolve toward symbiosis?

(A) Evolutionary theorists now postulate that symbiotic interactions generally evolve toward greater parasitism, rather than vice versa.
(B) The evolutionary tree of fungi is somewhat more complex than that of similarly parasitic or symbiotic organisms.
(C) The DNA of fungi involved in symbiotic interactions is far more difficult to isolate than that of fungi involved in parasitic interactions.
(D) The placement of lichen-forming fungi as a separate group on the fungus family tree masked the fact that parasitic fungi sometimes evolved much later than symbiotic ones.
(E) Branches of the fungus family tree that have evolved from symbiosis to parasitism usually die out shortly thereafter.[/box_in][/box_out][/align]


Here's what went through my head choosing the D on question 5 (the only answer i got wrong)
Ok so E states that the Fungus die after they convert from symbiosis to parasitism. this doesnt weaken the critic as the fungus still does convert into parasitism.
D on the other hand says that Fungi some time evolves much later into symbiotics. so that might mean that when the researchers saw the fungi, they did not yet evolve from parasitic to symbiotic and will become symbiotic after this step.

Kindly tell me where did i go wrong
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5. Which one of the following, if true, most weakens the author’s criticism of the assumption that parasitic interactions generally evolve toward symbiosis?

(A) Evolutionary theorists now postulate that symbiotic interactions generally evolve toward greater parasitism, rather than vice versa.
(B) The evolutionary tree of fungi is somewhat more complex than that of similarly parasitic or symbiotic organisms.
(C) The DNA of fungi involved in symbiotic interactions is far more difficult to isolate than that of fungi involved in parasitic interactions.
(D) The placement of lichen-forming fungi as a separate group on the fungus family tree masked the fact that parasitic fungi sometimes evolved much later than symbiotic ones.
(E) Branches of the fungus family tree that have evolved from symbiosis to parasitism usually die out shortly thereafter.[/align]


Here's what went through my head choosing the D on question 5 (the only answer i got wrong)
Ok so E states that the Fungus die after they convert from symbiosis to parasitism. this doesnt weaken the critic as the fungus still does convert into parasitism.
D on the other hand says that Fungi some time evolves much later into symbiotics. so that might mean that when the researchers saw the fungi, they did not yet evolve from parasitic to symbiotic and will become symbiotic after this step.

Kindly tell me where did i go wrong

This is the assumption that the author criticised:
parasitic interactions inevitably evolve over time to a greater benignity and eventually to symbiosis so that the parasites will not destroy their hosts

This is the author's criticism of the assumption:
Fungi both harmful and benign can now be found both early and late in fungus evolutionary history. Given the new layout of the fungus family tree resulting from the lichen study, it appears that fungi can evolve toward mutualism and then just as easily turn back again toward parasitism.

The right answer needs to show that the author's criticism may be wrong and the old assumption may be valid.

Why (E) is right:
(E) Branches of the fungus family tree that have evolved from symbiosis to parasitism usually die out shortly thereafter"
(E) says that branches of the family tree that evolve towards parasitism usually die out. This fact would STRENGTHEN the old assumption and thus WEAKEN the author's criticism, because it means the overall trend IS towards greater benignity and symbiosis. So (E) is the answer we want.

Why the justification of (D) is wrong:
(D) ... parasitic fungi sometimes evolved much later than symbiotic ones.
(D) does not say that "Fungi some time evolves much later into symbiotics"! Anyway, even if (D) had said so, it would not weaken the author's criticism.
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Its_me_aka_ak
5. Which one of the following, if true, most weakens the author’s criticism of the assumption that parasitic interactions generally evolve toward symbiosis?

(A) Evolutionary theorists now postulate that symbiotic interactions generally evolve toward greater parasitism, rather than vice versa.
(B) The evolutionary tree of fungi is somewhat more complex than that of similarly parasitic or symbiotic organisms.
(C) The DNA of fungi involved in symbiotic interactions is far more difficult to isolate than that of fungi involved in parasitic interactions.
(D) The placement of lichen-forming fungi as a separate group on the fungus family tree masked the fact that parasitic fungi sometimes evolved much later than symbiotic ones.
(E) Branches of the fungus family tree that have evolved from symbiosis to parasitism usually die out shortly thereafter.[/align]


Here's what went through my head choosing the D on question 5 (the only answer i got wrong)
Ok so E states that the Fungus die after they convert from symbiosis to parasitism. this doesnt weaken the critic as the fungus still does convert into parasitism.
D on the other hand says that Fungi some time evolves much later into symbiotics. so that might mean that when the researchers saw the fungi, they did not yet evolve from parasitic to symbiotic and will become symbiotic after this step.

Kindly tell me where did i go wrong

This is the assumption that the author criticised:
parasitic interactions inevitably evolve over time to a greater benignity and eventually to symbiosis so that the parasites will not destroy their hosts

This is the author's criticism of the assumption:
Fungi both harmful and benign can now be found both early and late in fungus evolutionary history. Given the new layout of the fungus family tree resulting from the lichen study, it appears that fungi can evolve toward mutualism and then just as easily turn back again toward parasitism.

The right answer needs to show that the author's criticism may be wrong and the old assumption may be valid.

Why (E) is right:
(E) Branches of the fungus family tree that have evolved from symbiosis to parasitism usually die out shortly thereafter"
(E) says that branches of the family tree that evolve towards parasitism usually die out. This fact would STRENGTHEN the old assumption and thus WEAKEN the author's criticism, because it means the overall trend IS towards greater benignity and symbiosis. So (E) is the answer we want.

Why the justification of (D) is wrong:
(D) ... parasitic fungi sometimes evolved much later than symbiotic ones.
(D) does not say that "Fungi some time evolves much later into symbiotics"! Anyway, even if (D) had said so, it would not weaken the author's criticism.



Ohhhhhh I realise now that i read the option D wrong
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