Juaz wrote:
Extinction is a process that can depend on a variety of ecological, geographical, and physiological variables. These variables affect different species of organisms in different ways, and should, therefore, yield a random pattern of extinctions. However, the fossil record shows that extinction occurs in a surprisingly definite pattern, with many species vanishing at the same time.
Which of the following, if true, forms the best basis for at least a partial explanation of the patterned extinctions revealed by the fossil record?
(A) Major episodes of extinction can result from widespread environmental disturbances that affect numerous different species.
(B) Certain extinction episodes selectively affect organisms with particular sets of characteristics unique to their species.
(C) Some species become extinct because of accumulated gradual changes in their local environments.
(D) In geologically recent times, for which there is no fossil record, human intervention has changed the pattern of extinctions.
(E) Species that are widely dispersed are the least likely to become extinct.
There is a paradox here: Extinction depends on lots of factors that are different for different species (their geography, their physiology etc). Still we see many species vanishing at the same time. Why?
(A) Major episodes of extinction can result from widespread environmental disturbances that affect numerous different species.
Major widespread environmental disturbances (environmental issues covering many geographies) affect many different species at the same time. Hence this could explain why many species become extinct together. So say an Earth wide warming could affect many species and cause their extinction within a few years. Hence, this is the answer.
(B) Certain extinction episodes selectively affect organisms with particular sets of characteristics unique to their species.
This tells us that effect is selective on organisms based on their unique characteristics. It does not explain why many organisms get affected together. They should not if the effect is selective.
(C) Some species become extinct because of accumulated gradual changes in their local environments.
This talks about "some species" and their "local environment". Hence it does not explain widespread effect to many species
(D) In geologically recent times, for which there is no fossil record, human intervention has changed the pattern of extinctions.
This tells us that we have changed the pattern of extinctions. The argument questions why there is a pattern of extinctions to begin with. Whether it is changing and how and because of whom are all irrelevant discussions.
Our point is - why does a widespread pattern of extinction exist? Many species have been getting affected simultaneously for millions of years (as per fossil records). Why do these species get affected at the same time?
For recent times, we don't even have fossil records and our argument is not discussing these times. We are discussing the times for which we have fossil records. Hence (D) is out of scope.
(E) Species that are widely dispersed are the least likely to become extinct.
This tells us what kind of species would be least likely to get affected simultaneously. It doesn't provide us the explanation we are seeking.
Answer (A)