Fish with teeth specialized for scraping algae occur in both Flower Lake and Blue Lake. Some biologists argue that be...

Masada on May 13, 2020

Explanation please

hello can I get a break down of the question and also the answer choices. ( B and C )

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Victoria on May 13, 2020

Hi @Masada,

Happy to help!

The passage tells us that fish with rare specialized algae-scraping teeth occur in both Flower (F) and Blue (B) Lakes.

Some biologists expect that, due to the rarity of specialized characteristics, fish which have these teeth should be closely related.

If the fish are closely related, then the specialization evolved only once.

CR --> SEO

Not SEO --> Not CR

The passage then concludes that the specialization evolved more than once. Why? Because the two fish species in Lakes B and F are not closely related.

We are looking for the error in reasoning made in the passage.

The passage uses the fact that the species are not closely related to conclude that the specialization evolved more than once. Notice that this reasoning is a reversal of the contrapositive statement above.

The passage confuses the sufficient condition with the necessary one in drawing its conclusion. This is directly restated by answer choice (C), making it the correct answer.

Answer choice (B) is incorrect because, while their exact relation has not yet been confirmed, the fact that the two fish species are not closely related has been confirmed. Therefore, this does not describe what has occurred in the passage.

Hope this is helpful! Please let us know if you have any further questions.

Masada on May 14, 2020

Thank you so much !