As discussed in the first paragraph of the passage Sanders' analogy between the deep sea and the Amazon basin involve...

Jacob-R January 28, 2019

I’m happy to help, Shiyi-Zhang. In order to understand why C is correct, and why A is wrong, let’s look at the question prompt.

We know right away that we are looking for something discussed in the first paragraph of the passage. That helps us narrow our search. We are asked about the analogy between the deep sea and the Amazon basin, and what assumptions that analogy involves. So what, exactly, was the analogy?

We know that Sanders discovered high diversity among mud-dwelling animals of the ocean, and argued that the diversity could be attributed to the absence of fluctuations in climate and physical conditions. This is because the absence of those conditions makes extinction rare, which allows new species to evolve, with greater accumulation of diversity.

And we also learn that Sanders argued that the Amazon tropical rain forest is ANALOGOUS (note the question stem signal word!) because the forest has a stable climate, and thus extinction should be rare. And then we get a piece of supporting evidence: some species of rain-forest trees have persisted for some 30 million years in the Amazon, and there is an absence of winter and glaciacion.

What is the assumption that connects those two examples? We learn that both the deep ocean and Amazon basin have long-existing species because of an absence of fluctuation in climate and physical conditions. For the latter, it is described as “stable climate” and “an absence of winter and glaciacion.”

And that is exactly what answer C says, which is why it is correct.

Answer E is incorrect because we don’t know that the rate of speciation of the two places is EQUILVALENT, but instead that the two places share features that makes species last for a long time.

I hope that helps! Please let us know if you have further questions.

Shiyi-Zhang January 30, 2019

Why is A incorrect?

Ravi January 31, 2019

@Shiyi-Zhang,

Great question. (A) is incorrect because the analogy does not depend
on the assumption that both the Amazon basin and the deep sea support
an unusually high rate of speciation.

We're told in lines 10 through 14 that "In the course of time new
species would continue to evolve, and so the rate of speciation would
be greater than the rate of extinction, resulting in the accumulation
of great diversity."

Right after this, the analogy between the deep sea and the rain forest
is introduced, with the idea that extinction in both regions should be
rare.

Lines 10 through 14 suggest that the analogy is pointing to the fact
that the rate of speciation simply being higher than the rate of
extinction. This doesn't necessarily mean that the rate of speciation
is unusually high—it could, in fact, not be that high, but as long as
it's higher than the rate of extinction, over time there will be tons
of diversity.

This is why (A) is not an assumption that analogy depends on.

Does that make sense? Let us know if you have any more questions!