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The tropical leaf-cutter, or attine, ant provides a remarkable example

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The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post Updated on: 13 Jan 2019, 07:19
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The tropical leaf-cutter, or attine, ant provides a remarkable example of complex symbiosis involving several species. The ants cultivate a fungus in underground caverns to serve as a source of food. DNA analysis reveals that the fungi in attine gardens around the world are clones of a single source. The ants do not allow their fungus crop to develop fruiting bodies, the means by which plants engage in sexual reproduction. Instead, a queen ant starting a new nest takes a sample of the fungus from the old nest to start the new garden, spreading the fungus vegetatively, or asexually.
For many years, the phenomenon of sexual reproduction puzzled biologists, as it passes only half of the parents’ genes to the succeeding generation and requires a more complex mechanism than does asexual reproduction. What benefit of sexual reproduction would outweigh these limitations? One likely answer is that it provides a defense against parasitic attack. Simple parasites, such as bacteria or molds, mutate rapidly and pose a challengeto other species developing defense mechanisms. The rapid evolution of the attacking species provides an advantage in this biological arms race. Sexual reproduction allows the more complex species to shuffle its genes between generations and, as a result, evolve quickly enough to match the parasites’ mutations.
A clonal monoculture, such as that of the attine, should be highly susceptible to parasites, yet preliminary research suggested no evidence of such a problem in the ants’ gardens. More comprehensive studies showed that the Escovopsis mold, a parasite related to the “green mold” known to commercial mushroom farmers, is present in the ants’ crops and poses a serious threat to the fungus. However, the attine ants provide the defense mechanism lacking in the fungus’s asexual reproduction by means of a bacterium that grows in patches on their skin. This actinomycete bacterium produces an antibiotic used to control the mold and limit its destructive effects on the ants’ food source.
Q1). The phrase “clonal monoculture” refers to which of the following?
A)The Escovopsis mold
B)A species of leaf-cutter ant
C)Sexual reproduction
D)A fungus
E)An antibiotic bacterium

Q2). Which of the following can be most reasonably inferred from the passage?
A)The fruiting bodies found on numerous fungi are a means of vegetative reproduction.
B)Plants that rely on sexual reproduction are highly susceptible to parasitic attack by bacteria and molds.
C)Sexual reproduction is an inefficient method for transmitting a parent’s genes to its offspring.
D)The bacterium found on patches of green mold produces an antibiotic substance used by commercial mushroom farmers.
E)Parasitic bacteria use sexual reproduction as a means to achieve rapid mutation.

Q3). The author describes the interaction between a parasite and a sexually reproducing organism as an “arms race” (line 22) in order to
A)emphasize the aggressive nature of the parasitic organism
B)warn of the dangers of biological weapons
C)underscore the need for the attine ants to defend their gardens
D)point out the devastating effects of the Escovopsis mold
E)depict the result of rapid evolution by both organisms

Q4). The passage suggests which of the following about the fungus grown by the attine ants?
A)By shuffling its genes, it is able to mutate rapidly in response to parasitic threats.
B)Due to its asexual reproduction, it is susceptible to attack by the actinomycete bacterium.
C)It could potentially engage in sexual reproduction.
D)It is closely related to the crops grown by commercial mushroom farmers.
E)Without the care of the attine ants, it would quickly become extinct.


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Originally posted by GmatWizard on 27 Dec 2018, 07:08.
Last edited by Gladiator59 on 13 Jan 2019, 07:19, edited 2 times in total.
Edited OA.
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 27 Dec 2018, 07:14
Hey guys workout u1983 Gladiator59
This is a 700 level passage from Princeton Review, but I don't have the Official Answers can you'll please help me out with this passage.
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 27 Dec 2018, 07:45
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I think the correct answers sequence should be D A E C.

Good passage but I doubt whether it is 700 level.

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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 27 Dec 2018, 07:52
Gladiator59 wrote:
I think the correct answers sequence should be D A E C.

Good passage but I doubt whether it is 700 level.

Regards,
Gladi

Thanks a lot.The book says it's supposed to be a difficult passage, but you never know I'm not sure how good are Princeton Review passages.
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 27 Dec 2018, 07:55
+1 kudos to the posts containing answer explanations of all questions
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 27 Dec 2018, 16:31
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I thought the passage was pretty interesting and understood it after one read, but still only got 2/4 correct...

Could someone explain 2 and 3?

How is 2 possible A? In the first paragraph it says "The ants do not allow their fungus crop to develop fruiting bodies, the means by which plants engage in sexual reproduction." Hence the fruiting bodies are for sexual reproduction. In the last sentence it also says "produce vegetatively, or asexually". Why does A consider the fruiting bodies to be a form of asexual reproduction when it clearly says it is sexual. For reference I chose C because in the 2nd paragraph it says "he phenomenon of sexual reproduction puzzled biologists, as it passes only half of the parents’ genes to the succeeding generation and requires a more complex mechanism than does asexual reproduction." It can be inferred here that sexual reproduction is inefficient...

For 3: I chose A, but was stuck between A and E. I can see why E is correct but I cannot see why A is incorrect.
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 12 Jan 2019, 09:08
Got 4/4 correct in 10 min total including 3:30 min to read the passage!

Passage Map:


1) Ant asexually produce fungus
2) Threat of parasite attack & benefit of sexual reproduction
3) Ant's solution to prevent parasite attack on their food: fungus
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 13 Jan 2019, 05:00
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Hi Gladiator59 , can you please explain the option A in question 2. My reasoning is same as that of kchen1994.

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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 13 Jan 2019, 07:18
Hi Mudit27021988, thanks for tagging me.

I must have missed the initial post by kchen1994 which explains nicely why Q2 should be (C) and not (A).
I agree that fruiting bodies are for sexual reproduction and hence option (A) is a classic 180 opposite example. Also, since it has puzzled scientists why sexual reproduction is preferred despite its "limitations" - it is also clear that it is not an efficient way of reproduction.

OA for Q2 has been changed to (C).

+1 kudos to both for pointing this out. :-)

Keep it up!
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 13 Jan 2019, 08:17
Got 2 incorrect.But awesome passage this!!!

Just to confirm once, is the answer to Q4) C because "The ants do not allow their fungus crop to develop fruiting bodies, the means by which plants engage in sexual reproduction"..??
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New post Updated on: 13 Jan 2019, 17:48
Precisely. The ants are said to not allow fruiting bodies to grow and hence prevent sexual reproduction. So there is a potential for sexual reproduction if for some reason the ants would stop "harvesting" the fungus. That's why (C) fits given its mild wording - "potential" being mild suggestion...

Another close option could be (E) "without the ants it would quickly become extinct" because the passage ends with this note.
However,I felt this option to be extreme given that the fungus was engaging in asexual reproduction because of the ants in the first place - in the absence of ants it would just start growing fruiting bodies and fall in the ambit of protection offered by sexual reproduction. Also, the wording on this option is extreme "quickly extinct" -we can only infer that there would be destruction of the fungus but whether it leads to quick extinction is open ended.

Hope this helps. I'd like to know your thoughts on this.

redskull1 wrote:
Got 2 incorrect.But awesome passage this!!!

Just to confirm once, is the answer to Q4) C because "The ants do not allow their fungus crop to develop fruiting bodies, the means by which plants engage in sexual reproduction"..??


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Originally posted by Gladiator59 on 13 Jan 2019, 08:43.
Last edited by adkikani on 13 Jan 2019, 17:48, edited 1 time in total.
edited typo
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example  [#permalink]

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New post 13 Jan 2019, 09:21
As you rightly said,I think "quickly" gives it up.....
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Re: The tropical leaf-cutter, or attine, ant provides a remarkable example &nbs [#permalink] 13 Jan 2019, 09:21
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