#22 - Because the native salmon in Lake Clearwater had

[nicholaspavic]

Hi swong,

Let me throw out on other idea that may illustrate a point - what if only one of the groups of sockeye bred with the natives? In other words, say the deepwater sockeye bred with the native salmon and ended up becoming the deepwater group as a result. Because that alternative cause is still getting eliminated with (A) as well.

Thanks for the great question!

[lrogue]

my practice test says that C is the answer

[Stephanie Oswalt]

Hi lrogue,

I'm seeing that the answer is A. Perhaps you're looking at the incorrect section?

Thanks!

[mkhabra]

I understand the explanation perfectly well. My question is more on the question stem. What is the difference between most strongly supported or strengthen questions? I felt that this was a most strongly supported question. Can you attack both the same way especially with a qs like this?

[Adam Tyson]

The difference in those two question types, mkhabra, is in the directional flow of information between the stimulus and the answer choices. In a Most Strongly Supported (which is a subset of Must Be True), the information in the stimulus is used to help prove one of the answers. That is, the information flows downward, from the stimulus to the answers. This is indicated in the stem by words like "the information above, if true..."

In a Strengthen question, on the other hand, the correct answer helps improve or explain the situation in the stimulus. The information flows upward from the answer to the stimulus (usually an argument that needs help). This is indicated by language in the stem such as "which of the following, if true..."

Both question types are about helping, or strengthening, but in one case the stimulus helps the answer, while in the other the answer helps the stimulus. It's very important to know which direction you are looking, so you can be sure you know what it is that you are trying to help! That will make a huge difference in what you might prephrase before looking at the answer choices!

[ange.li6778]

I originally had the cause and effect reversed like this:

cause: two populations now differ genetically
effect: each has adapted genetically to its distinct habitat.

I did so because I thought the last sentence of the stimulus could be rephrased as "Because the two populations are now genetically different, that means each has adapted to its habitat" and because 'since' sounds like an indicator of causation. Can we rely on 'since' and other words as indicators of cause, or is it not always an indicator?

[katehos]

Hi Ange,

The 'since' in this scenario refers to why the researchers believe genetic adaptation to the environment is the cause of the sockeye population split, as opposed to what actually caused the population split. Basically, it's just saying that the genetic difference is the evidence researchers relied on to determine that adaptation caused the genetic differences. So, the 'since' here is still an indicator of cause, just not the right one! It's not a great argument on the researcher's behalf (as they are assuming only one cause after observing an effect), which is part of why this argument needs strengthening! Hopefully that makes sense, let me know if it doesn't.

Also, it may be helpful to consider the relationship between the cause and effect to understand why the reverse of the cause/effect you wrote is correct! Try to think of it this way: is two populations now differing genetically, like how frogs are a genetically distinct species from dogs, a cause of adaptation? Or does it make more sense that two populations differing genetically, like dogs and frogs, is the end result/effect of adaptation? It's a bit of a silly/simple example, but hopefully it illustrates how if we simplify the relationship, we can see that the researchers believe adaptation caused the genetic differences.

Hope that helps!
-Kate

[rlouis1993]

Is the Distinct Habitat the cause and the genetic difference the effect?

[Jeff Wren]

Hi rlouis,

To be precise, the researchers hypothesize that the cause is that the salmon adapted genetically to their distinct habitats. In other words, it's not just the fact that these two groups of salmon are found in two different habitats, the researchers believe that the salmon genetically adapted to those habitats.

And you are correct that the genetic differences between the two groups are the effect that the researchers are trying to explain.

[sammohamed]

I think I finally got it by thinking of it like this.

The question asks about the researcher's hypothesis, which is stated to be that each distinct group of the new species of salmon adapted genetically to it's environment. But if they had instead simply mated with the previous species - which may have been adapted genetically to the same environment - then they wouldn't themselves have to undergo the process of adapting genetically. They would skip right to the end result of having fitness for this environment.

Despite the above, I feel this is not a great test question because it requires you to decide that achieving adapted genetics through mating is not itself genetic adaption. It would be a lot better if they had explained that adapting genetically means developing genetic mutations that allow subsequent generations to adapt to the environment.