A stingray without parasites is healthier than it would be if it had

Question

A stingray without parasites is healthier than it would be if it had parasites. Nevertheless, the lack of parasites in stingrays is an indicator that the ecosystem in which the stingrays live is under environmental stress such as pollution.

Which one of the following, if true, most helps to reconcile the discrepancy indicated above?

(A) During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which are environmentally vulnerable organisms.

(B) A stingray is a free-ranging predator that feeds on smaller organisms but has few predators itself.

(C) A parasite drains part of the vitality of its host by drawing nourishment from the host.

(D) An ecosystem can be considered stressed if only a few species of very simple organisms can live there.

(E) Since the life of parasites depends on that of their host, they need to live without killing their host or else to reproduce and infect other individuals before their own host dies.

Krishh9119 · Answer

A stingray without parasites is healthier than it would be if it had parasites. Nevertheless, the lack of parasites in stingrays is an indicator that the ecosystem in which the stingrays live is under environmental stress such as pollution.

Which one of the following, if true, most helps to reconcile the discrepancy indicated above?

Discrepancy: the lack of parasites in stingrays is an indicator that the ecosystem in which the stingrays live is under environmental stress such as pollution.
  We need an answer that tells us pollution is the reason behind lack of parasite.

(A) During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which are environmentally vulnerable organisms.
 parasites' food=shrimp or oysters
But shrimp or oysters are environmentally vulnerable organisms.
So, pollution reduces 'parasites' food' , which in turn decreases parasites in stingrays.

(B) A stingray is a free-ranging predator that feeds on smaller organisms but has few predators itself.
 Out of Scope .

(C) A parasite drains part of the vitality of its host by drawing nourishment from the host.
 Out Of Scope.

(D) An ecosystem can be considered stressed if only a few species of very simple organisms can live there.
 Irrelevant

(E) Since the life of parasites depends on that of their host, they need to live without killing their host or else to reproduce and infect other individuals before their own host dies.
 Irrelevant.

A is our answer.

globaldesi · Answer

IMO D
(D) An ecosystem can be considered stressed if only a few species of very simple organisms can live there.
since parasites are a simple living organism , having a lack of such indicates that enviroment is not able to sustain a lot of parasites.

Thus D helps resolve the depenency

shameekv1989 · Answer

A stingray without parasites is healthier than it would be if it had parasites. Nevertheless, the lack of parasites in stingrays is an indicator that the ecosystem in which the stingrays live is under environmental stress such as pollution.

Which one of the following, if true, most helps to reconcile the discrepancy indicated above?

(A) During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which are environmentally vulnerable organisms.

(B) A stingray is a free-ranging predator that feeds on smaller organisms but has few predators itself.

(C) A parasite drains part of the vitality of its host by drawing nourishment from the host.

(D) An ecosystem can be considered stressed if only a few species of very simple organisms can live there.

(E) Since the life of parasites depends on that of their host, they need to live without killing their host or else to reproduce and infect other individuals before their own host dies.

SR healthy - when no parasites
not healthy - with parasites

no parasites - indicator of pollution, in which stingrays live

healthy stingrays live in environmental conditions which are unheathy in general such as pollution. Why?

if parasites require hosts that can not live in pollution, parasites can not live in such conditions either. And thus stingrays would be healthier there. i.e. to put into statements argument is trying to convey :- 
lack of parasites -> indicator of pollution area - stingray lives in such areas
lack of parasites because they don't find shrimps or oysters needed for them to feed on. - thus stingray thrives in such areas

Answer - A

BIGDAMNGOD · Answer

Parasites are bad for stingrays. But their absence is bad news for the ecosystem in which 
the stingrays live. That’s the shift. How could parasites be good for the ecosystem even 
though they are bad for some of the residents of that ecosystem?
 
If (A) is true, and stingray parasites depend on other environmentally vulnerable 
organisms, then the presence of the parasite is an indicator of the presence of those other
organisms. The parasites are still bad news for the stingray, but they could be good news 
for the ecosystem. If the parasites are around, then the species they depend on must be 
present as well, which supports the notion that the system isn’t under stress. But if the 
parasites are missing, then maybe those other species are missing, too, and this in turn 
would support the notion that environmental stresses have taken a toll on vulnerable 
organisms such as the shrimp and the oyster.

(B) is useless background information.
 
(C) explains why parasites are bad for stingrays (or any hosts), but we knew that already.

(D) is too broad: A general statement about what might constitute environmental stress 
doesn’t help us to resolve the puzzle posed in the stimulus—why is something that’s bad
for an inhabitant of an environment a positive sign for the environment as a whole?

(E) explains why parasites cannot be too hostile to their hosts, but doesn’t connect 
stingray parasites to the ecosystem in general.

Alexdb10 · Answer

Lets break the stimuli down into two parts

First Statement (S1): A stingray without parasites is healthier than it would be if it had parasites.

Second Statement (S2): Nevertheless, the lack of parasites in stingrays is an indicator that the ecosystem in which the stingrays live is under environmental stress such as pollution.

Which of the following if true reconciles the discrepancy indicated above? - Lets establish the discrepancy. (S1) leads us to believe that parasites are negative, at least in relation to Stingrays. (S2) Tells us that they are a positive indication for the environment.

Thus the discrepancy here and what the question is really asking is: How can parasites be bad for Stingrays, yet a positive indicator for the environment?

Option A: During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which are environmentally vulnerable organisms.

Reading this answer it explains that for parasites to survive, they require the existence of Shrimp or Oysters. It goes on to explain that Shrimp and Oysters are environmentally vulnerable organisms. Therefore a lack of parasites in stingrays, would be indicative of poor environmental conditions  in spite  of their negative effects on Stingrays.

Answer: A

bharathhr · Answer

Establishing the discripency was challenging it seems , there is no discrepency. no parasites ---sting ray are healthy , and environment is bad. Is it right of me to think there is no apperent discripency

bhanu29 · Answer

Fair doubt, but there is one. It's just hidden in the logic, not stated directly.

Normal expectation: no parasites = clean, healthy environment.
 Stimulus says: no parasites = polluted, stressed environment.

That's the paradox. Something that sounds like good news (parasite-free) is being used as bad news (pollution signal). That's weird, and "nevertheless" is pointing right at that weirdness.

A fixes it, parasites aren't gone because things are clean, they're gone because pollution killed off the shrimp/oysters they need to survive. Stingray itself is tough enough to shrug off the pollution, so it looks fine. But no parasites really means "something died off," not "environment is clean."

egmat · Answer

Hi bharathhr,

Good instinct to slow down and check whether a real discrepancy even exists, because if there isn't one, the whole question falls apart. But there  is  one here, and it's easy to miss the way you framed it.

You lined up the facts like this: no parasites means a healthier stingray, and the environment is bad. Read that way, they  look  like two separate, compatible facts. The tension only appears when you ask what a "healthier animal" and a "bad environment" normally go together with.

Where the paradox lives

Normally, a  healthier  animal is a sign of a  healthier  environment. That's the default expectation. Now look at what the stimulus actually says:

- Losing parasites makes the stingray  healthier  (good for the animal).
-  Nevertheless , that same parasite-free state signals the ecosystem is  under stress  (bad for the environment).

So the very thing that improves the individual stingray is a warning sign that its home is polluted. That's the clash: a  positive  for the animal doubling as a  negative  indicator for the ecosystem. The word  "Nevertheless"  is the flag; it's telling you these two facts pull in opposite directions.

That's also why choice  A  is the fix: it explains  why  a good-for-the-stingray fact (no parasites) is  bad news  for the ecosystem. The parasites need environmentally fragile shrimp and oysters, so their disappearance means those vulnerable species have died off.

A quick stand-in to feel the tension

"People who have given up smoking are healthier than people who still smoke.  Nevertheless , a sharp rise in the number of people who quit smoking in a town is bad news about that town's health."

For each person, quitting is a clear win. But a sudden wave of quitters is alarming, because people usually quit  after  a diagnosis or a scare. Good for the individual, bad news about the group. That is exactly the shape of your stingray argument, and once you feel that pattern you stop reading the two facts as merely agreeable and start hunting for what reconciles them.

Answer: A

A stingray without parasites is healthier than it would be if it had

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A stingray without parasites is healthier than it would be if it had

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