A lichen consists of a fungus living in symbiosis (i.e., a mutually be

Question

A lichen consists of a fungus living in symbiosis
(i.e., a mutually beneficial relationship) with an alga.
Although most branches of the complex evolutionary
family tree of fungi have been well established, the
  (5)   evolutionary origins of lichen-forming fungi have
been a mystery. 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,
  (10)   lichen-forming fungi are close relatives of such
common fungi as brewer’s yeast, morel mushrooms,
and the fungus that causes Dutch elm disease. This
accounts for the visible similarity of certain lichens to
more recognizable fungi such as mushrooms.

(15)   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
  (20)   difficult to study. They have few distinguishing
characteristics of shape or structure, and they are
unusually difficult to isolate from their partner algae,
with which they have a particularly delicate
symbiosis. In some cases the alga is wedged between
  (25)   layers of fungal tissue; in others, the fungus grows
through the alga’s cell walls in order to take
nourishment, and the tissues of the two organisms are
entirely enmeshed and inseparable. As a result,
lichen-forming fungi have long been difficult to
  (30)   classify definitively within the fungus family. By
default they were thus considered a separate grouping
of fungi with an unknown evolutionary origin. But,
using new analytical tools that allow them to isolate
the DNA of fungi in parasitic or symbiotic
  (35)   relationships, researchers were able to establish the
DNA sequence in a certain gene found in 75 species
of fungi, including 10 species of lichen-forming
fungi. Based on these analyses, the researchers found
5 branches on the fungus family tree to which
  (40)   varieties of lichen-forming fungi belong. Furthermore,
the researchers stress that it is likely that as more
types of lichen-forming fungi are analyzed, they will
be found to belong to still more branches of the
fungus family tree.

(45)   One implication of the new research is that 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
  (50)   destroy their hosts. The addition of lichen-forming
fungi to positions along branches of the fungus
family tree indicates that this assumption does not
hold for fungi. Fungi both harmful and benign can
now be found both early and late in fungus
  (55)   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.    1 
 1. Which one of the following most accurately states the main point of the passage?

(A) New research suggests that fungi are not only parasitic but also symbiotic organisms.
(B) New research has revealed that lichen-forming fungi constitute a distinct species of fungus.
(C) New research into the evolutionary origins of lichen-forming fungi reveals them to be closely related to various species of algae.
(D) New research has isolated the DNA of lichenforming fungi and uncovered their relationship to the fungus family tree.
(E) New research into the fungal component of lichens explains the visible similarities between lichens and fungi by means of their common evolutionary origins.

2 
 2. Which one of the following most accurately describes the author’s purpose in the last paragraph of the passage?

(A) to suggest that new research overturns the assumption that lichen-forming fungi are primarily symbiotic, rather than parasitic, organisms
(B) to show that findings based on new research regarding fungus classification have implications that affect a long-standing assumption of evolutionary science
(C) to explain the fundamental purposes of fungus classification in order to position this classification within the broader field of evolutionary science
(D) to demonstrate that a fundamental assumption of evolutionary science is verified by new research regarding fungus classification
(E) to explain how symbiotic relationships can evolve into purely parasitic ones

3 
 3. Which one of the following most accurately describes the organization of the passage?

(A) explanation of the difficulty of classifying lichens; description of the DNA sequence of lichen-forming fungi; summary of the implications of this description
(B) definition of lichens; discussion of new discoveries concerning lichens’ evolutionary history; application of these findings in support of an evolutionary theory
(C) definition of lichens; discussion of the difficulty in classifying their fungal components; resolution of this difficulty and implications of the resulting research
(D) discussion of the symbiotic relationship that constitutes lichens; discussion of how new research can distinguish parasitic from symbiotic fungi; implications of this research
(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

4 
 4. According to the passage, the elimination of which one of the following obstacles enabled scientists to identify the evolutionary origins of lichen-forming fungi?

(A) The DNA of lichen-forming fungi was not easy to separate from that of their associated algae.
(B) Lichen-forming fungi are difficult to distinguish from several common fungi with which they are closely related.
(C) Lichen-forming fungi were grouped separately from other fungi on the fungus family tree.
(D) Lichen-forming fungi are far less common than more recognizable fungi such as mushrooms.
(E) The DNA of lichen-forming fungi is significantly more complex than that of other fungi.

5 
 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.

TathagataC · Answer

Can anyone please explain question number 5?
Why the answer is option E, not A.

Sajjad1994 · Answer

Hi TathagataC

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.

(A)  is opposite. Evidence of movements from symbiosis to parasitism actually support the author’s viewpoint.

BITTU1234 · Answer

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

Sajjad1994 · Answer

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.

vv65 · Answer

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
 and introduces a puzzle ('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.
 
Para 2 gives reasons why fungi in general and lichen fungi in particular are hard to study.
 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 
 The para then tells us how new tools have helped researchers
 
Para 3, the final para, tells us an implication of the new study: an old belief has been weakened.
 Para 3 then explains how this belief was weakened by the new findings.

Posted from my mobile device

TryingToAceVerbal · Answer

Can anyone provide an explanation for Q3?

vv65 · Answer

This is the question
 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.

- The passage does not describe the DNA sequence of the fungi.
- This answer does not even mention the new research.

- 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.

All good!

- 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.

- This answer does not even mention the new research.

C is the clear answer.

Posted from my mobile device

Its_me_aka_ak · Answer

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.

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

vv65 · Answer

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.

Its_me_aka_ak · Answer

Ohhhhhh I realise now that i read the option D wrong

VerbalBot · Answer

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A lichen consists of a fungus living in symbiosis (i.e., a mutually be

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A lichen consists of a fungus living in symbiosis (i.e., a mutually be

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