#21 - The similarity between ichthyosaurus and fish

[JennuineInc]

Hi,

Can someone please help me diagram this conditional statement. I answered D correctly with an inkling that it may have been a conditional statement but I don't know how that statement would look for both the stimulus and answer. I guess I don't see any conditional indicators.

D. One or more similar external features doesn't mean same class because it could be due to convergence.

Thank you!

[Clay Cooper]

Hi Jennuine,

Thanks for your question.

The conditional reasoning that I see in this stimulus is:

Ichthyosaur marine reptile ~fish
ichthyosaur has fins

I am not sure that D is a positive conditional statement; if anything, I think, it is a statement of uncertainty, so to speak. All it tells us is that having a particular body feature is not enough to make you a member of a particular class of which that feature is typical.

That said, we can still prove D by referring back to our evidence about ichthyosaurs. We know they have fins, and we know that they are not fish, but marine reptiles. Therefore, we can prove that an animal (e.g. an ichthyosaur) is not necessarily a member of a particular class of animals (e.g. fish) even if it possesses features typical of that class (e.g. fins).

Does that make sense?

[JennuineInc]

Yeah it makes sense. Thank you. It seems easier to do this problem without the conditional statements!

[lrogue]

Can you please explain to me why it is not C?

[Adam Tyson]

Thanks for the question, lrogue! The stimulus gives us enough information to know that in at least some cases, two different organisms could "converge", developing similar features due to adapting to the same environment. We know this is true of ichthyosaurs and fish. But do we know that this is the only way those similarities could develop? What if two different organisms developed similar features despite being in very different environments? Like, maybe some fish have eyes that move independently and on opposite sides of the head, and some lizards have the same features, even though fish and lizards live in very different environments? This would have to be due to something other than convergence. The stimulus doesn't rule this out, and so answer C is not supported by the passage. Convergence is one way that similarities can develop, but it doesn't have to be the only way!

Be wary of answers as strong as C when analyzing Must Be True and Most Strongly Supported questions. Those are often trap answers! Look out for words like only, and best, and required, and always, and never, etc. To prove strong words like those, you need strong evidence! Those types of answers can be correct, but only when the evidence is correspondingly as certain and strong.