DiyaDutta wrote:
5. The author's argument that increased straying can "lower the overall fitness of subsequent generations" (see hightlited text) is based on which of the following assumptions?
(A) A disturbance of salmonid spawning streams caused by human activity could increase the straying rate of affected salmonid populations as much as the aftermath of the Mount Saint Helens eruption did.
(B) In the streams in which the straying salmonids spawn, these straying salmonids would amount to no more than 40 percent of the total spawning population
(C) Salmonids in some streams benefit from particular local adaptions.
(D) Nonenvironmental factors have no effect on salmonid straying rates.
(E) At least some of the streams in which straying salmonids would spawn are pristine, affected by neither natural nor artificial disturbances.
I am trying to understand the answer to this question and i read an explanation by mikemcgarry in a previous post. So as per my understanding "lower the overall fitness of subsequent generations" this is caused by straying of salmon from damaged areas to more pristine areas(as mentioned in the last paragraph) and high rates of straying can dilute local adaptations.(as mentioned in second paragraph) Hence we can infer that salmonids in some streams benefit from particular local adaptations. Can someone please confirm if my thinking is correct?
Manas1212 wrote:
5. The author's argument that increased straying can "lower the overall fitness of subsequent generations" (see hightlited text) is based on which of the following assumptions?
(A) A disturbance of salmonid spawning streams caused by human activity could increase the straying rate of affected salmonid populations as much as the aftermath of the Mount Saint Helens eruption did.
(B) In the streams in which the straying salmonids spawn, these straying salmonids would amount to no more than 40 percent of the total spawning population
(C) Salmonids in some streams benefit from particular local adaptions.
(D) Nonenvironmental factors have no effect on salmonid straying rates.
(E) At least some of the streams in which straying salmonids would spawn are pristine, affected by neither natural nor artificial disturbances.
Hi
GMATNinjaI got the above question wrong and while articulating my confusion here , I ended up with a better reasoning.(As you have mentioned this in one of your previous posts here)
Here is my reasoning :
The author says INCREASED straying could
lower the fitness of the subsequent generations(presumably in the foreign habitat.
So Does that mean the author thinks "Normal Straying increases/benefits the local fitness?"
If so, then C would be the answer.
Please tell me whether my reasoning is correct. Or please add on to it if my should have been better
Sorry for not replying sooner,
Manas1212! I think you are both on the right track here...
The passage specifically tells us that "
low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear."
But the very next sentence says, "Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted." According to the author, high rates of straying are bad because they dilute any local adaptations that are present. Okay, that sounds reasonable enough... but what if those local adaptations do not actually benefit the salmonids in any way?
For example, maybe a local population has developed a certain color in response to certain characteristics of the local water. If that change in color doesn't actually help the salmon at all, then it would be an example of a local adaptation that does not actually benefit the salmonids.
But if salmonids in some streams DO benefit from particular local adaptions, then passing those traits to future generations would obviously improve the overall fitness of future generations. Now if a bunch of non-local salmonids come in and diluate those adaptations, a lower percentage of the next generation will have that beneficial adaptation. That would of course
lower the overall fitness of future generations.
It might seem a bit ridiculous at first, but unless we assume that salmonids in some streams benefit from particular local adaptions, then we can't argue that increased straying would be harmful to the fitness of future generations. That's why (C) is correct!
warrior1991 wrote:
VeritasKarishma GMATNinja VeritasPrepHailey generisCan you please explain how in the below question the answer is D???
2. It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
(A) pristine streams that are near polluted streams become polluted themselves
(B) the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
(C) the number of salmon in pristine habitats decreases relative to the number in polluted streams
(D) an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
(E) the extinction of the salmon populations that spawn in polluted streams is accelerated
Have you checked out
this post? If that doesn't help, let us know what you are struggling with (be as specific as possible!).
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