nightblade354 wrote:
Even the earliest known species of land animals, known from fossils dating from the late Silurian period, 400 million years ago, show highly evolved adaptations to life on land. Since neither aquatic nor amphibious animals exhibit these adaptations, early species of land animals must have evolved very rapidly after leaving an aquatic environment.
Which one of the following is an assumption on which the argument depends?
Identify the argument: "early species of land animals must have evolved very rapidly after leaving an aquatic environment."nightblade354 wrote:
(A) Known fossils of early land animals include fossils of animals that lived relatively soon after the first emergence of land animals
Let's negate this answer choice.(A) Known fossils of early land animals
do not include fossils of animals that lived relatively soon after the first emergence of land animals.
Wait, we don't have fossils of early land animals? If we don't even have fossils of early land animals, how can we make the argument about early land animals showing highly evolved adaptations to life on land?
This wrecks our argument. Hold.nightblade354 wrote:
(B) Fossils from the late Silurian period represent only a small number of the animal species that were alive at that time
This assumption would weaken the argument. The argument does not depend on this assumption.nightblade354 wrote:
(C) No plants were established on land before the late Silurian period
"Plants" are way out of scope. We don't need to assume anything about "plants" for this argument.nightblade354 wrote:
(D) No present-day species of aquatic animal is descended from a species of animal that once lived on land
First of all, this is some strong language, which we should be cautionary of in Assumption questions. Let's negate this answer choice and see if it wrecks the argument. If it does, this is our answer.(D)
No Some present-day species of aquatic animals are descended from a species of animal that once lived on land.
Okay so if some animals evolved by going from land to water. Interesting... But that doesn't have anything to do with our argument. Our argument is about evolution of land animals going from water to land. So this choice is irrelevant. nightblade354 wrote:
(E) All animals alive in the late Silurian period lived either exclusively on land or exclusively in the water
Once again, we have some strong language; we'll proceed with caution.
Animals that live on land or in the water are amphibians. This assumption says that we didn't have any amphibians in the Silurian period. This doesn't have anything to do with the argument. Further, the last sentence of the stem says that amphibians didn't exhibit the adaptations. So whether we had amphibians or not, they did not show highly evolved adaptations to life on land. _________________
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06 May 2019, 04:47
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