PrepTest 103

Incorrect. This suggests that they're suffering from the lack of these traits—making it even more confusing that they lost them!

Incorrect. Their size doesn't explain why they lost what would be helpful traits. If anything, them being larger than their ancestors would suggest they'd get more use out of things that would help them stay in trees.

Incorrect. At most, this answer suggests that the tree-dwelling kangaroos lost these traits less than the land-dwelling ones, which makes sense. However, it doesn't explain why they lost the traits that conferred an advantage at all!

Correct. Argument or Facts:
Facts

Question Type:
Paradox

Stimulus Summary:
Kangaroo (tree and land) ancestors - Had some traits good for tree living, but not so good for land living
(Modern land kangaroos - Lost these traits)
Modern tree kangaroos - Lost these traits

Answer Anticipation:
As with all Paradox questions, we should start by clearly defining the paradox.

Here, we learn that, at some point, all kangaroos had traits that helped them to live in trees. What's the weird paradox? That modern tree-dwelling kangaroos have lost these traits—it seems as if they would have been helpful, so how did they lose them?!?!

That's a bigger question of evolution than we can be expected to know, so it's hard to form a direct anticipation. Luckily, there's a piece of information in here that makes more sense that we can use to help us out!

That piece of information is that the modern land kangaroos have also lost these traits. That makes sense since the traits don't really help animals that live on land.

So we have something that makes sense—a certain group of kangaroos that lost a trait—and one that doesn't—another group that lost it that doesn't make sense. If we put these together, we can come up with a process that does make sense. What if the land-dwelling kangaroos lost their tree-dwelling traits, and then some of them ended up switching back to being tree-dwelling kangaroos? That would make sense of why they lost the traits, so it's one potential answer. Any other potential answer we'll need to stay open to, because we're just not seeing it.

Answer Explanation:
This answer creates a timeline that explains what could have happened. If the old kangaroos evolved into land-dwelling kangaroos, then it makes sense that they'd lose the tree-dwelling traits. If those kangaroos then evolved back into tree-dwelling ones, they wouldn't necessarily get these traits back. Since this makes sense of the situation, it's the correct answer.

Key Takeaway:
When a Paradox question brings up a piece of information that seems to make sense, one of two things is generally true. It's either in there to distract you, or it's in there to serve as the basis for an explanation. Ask yourself if the part that makes sense is connected to the part that isn't, and if it is, try to connect them. Here, they both talked about kangaroos that lost certain traits, so they were connected.

Incorrect. The tree-dwelling kangaroos lacking traits that seem to be helpful to land-dwelling kangaroos would, if anything, provide evidence against the possibility that we anticipated as being the explanation here!