The three-spine stickleback is a small fish that lives both in oceans and in freshwater lakes. While ocean sticklebac...

Ravi on May 3, 2020

@Alexander-Blankers, great question. The problem with what that rationale is that we don't necessarily know that having more surface area would be a bad thing. With (C) as it's written, we need more information in order for it to work. We don't know whether or not being large is a good or bad thing if for the stickleback when it's trying to defend itself against insects. It's possible that being large is a really good defense against insects. We simply don't know either way, so that's why (C) doesn't weaken the argument.

Also, to play devil's advocate: what if the insects only could attack through one small area on the body that was independent of the size of the fish? If that were the case, then surface area wouldn't negatively impact the survival odds of the stickleback against insects.

Ravi on May 3, 2020

Let us know if you have any other questions!

Ravi on May 3, 2020

Also, regarding why (B) works: if (B) is true, then maybe the lake stickleback has to be really big to live through the winter. In that case, it could mean that the predator defense doesn't have anything to do with the relatively large size of the stickleback fish, so this is why (B) weakens the argument and is the correct answer choice.

SawyerJeppson on August 12, 2021

Hi, i am still a bit confused. The stimulus ends with the conclusion that "having a larger size is a better defense against the lake stickleback's predators than having armor". Even if it were true that lake sickleback need to be bigger in order to survive the cold, this doesnt rule out the possibility that larger size is also a better defense against their predators as another function of their size.

SawyerJeppson on August 12, 2021

In addition, wouldn't answer choice C also make sense because if we are trying to weaken the conclusion that larger size is a better defense than armor for lake sickleback, having armor would presumably better defend against insects than none at all. thereby showing that armor may actually be a better defense against predators than larger size?

Kasra on August 12, 2021

Hi,

how are we making the jump from the mere assertion that "having a larger size is a better defense against the lake stickleback's predators than having armor" to this being believed by the author to explain why ocean stickleback have armor and lake stickleback do not?

It also seems entirely consistent that a lake stickleback's size both enables it to survive the cold winters, and is a better defense against its predators than having armor. So, I fail to see how the answer choice weakens the argument.

legallybuddha on September 6, 2022

I have the same inclinations as the people in the comments above^^

The conclusion is "this indicates that having a larger size is a better defense against the lake stickleback's predators than having armor."

I thought C was the better answer choice than B because it effectively weakens the claim that the lake stickleback's size is a better defense than the armor. If it were true that lake stickleback were preyed on by insects, that would indicate a better need for the armor. I was thrown off by B because i feel like it barely impacts the claim, if anything it strengthens it a bit explaining why the lake stickleback's evolution to a bigger size is advantageous for its survival.

Emil-Kunkin on September 21, 2022

Hi, we are trying to weaken the idea that there lake fish do not have armor because the more effective defense int he lake is to be bigger, not armored.

I dont think that C tells us anything about the relative strengths of thee two defense mechanism. I know nothing about the feeding habits of fish as opposed to predatory insects. Who is to say if being preyed on by insects means you would need better armor? Furthermore, maybe it is simply the case that there are no insects in the ocean, so they are not able to eat the fish there.

As you pointed out, B explains why the lake fish need to be bigger. It suggests an alternative reason why they have no armor- that is, they lost the armor not to defend against predators, but to survive the winter.