Columnist: Contrary to what many people believe, the number of species on Earth is probably not dwindling. Extinction...

Ava on March 29, 2020

Answer choices E and A

Can someone explain why answer choices E is wrong and A is correct? I chose E because I thought if we had more species identified as extinct now than before, it would mean that the number of species is actually decreasing. But now I think what I missed in answer choice E is the use of the term facing extinction it is not actually talking about the number/amount of species going extinct. Is this a correct assumption? Additionally, it would be really helpful to see a formal explanation of how answer choice A weakens compared to the rest of the answer choices. Thanks in advance!

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on April 3, 2020

Hello @shafieiava,

Let's break down this argument. The author claims that there is "no reason to doubt" that new species emerge at the same rate that others go extinct. We must accept the premise that about as many species will go extinct this year as in 1970. However, that is only half of the equation. We have no information about new species emerging. How can we conclude that the rate is the same?

Answer choice A is correct because it causes the author's argument to backfire. He has based his conclusion on information from the 1970. If A is true, then his premise would lead to the opposite conclusion. The number of species on Earth did dwindle in 1970! This gives us a good reason to doubt that species emerge at the same rate as they go extinct.

I understand what you were thinking with E, and your reassessment is correct. E only says scientists today can better identify species "facing risk of extinction." This in no way implies that we are able to prevent these extinctions, nor does it imply that there will be fewer extinctions this year. Research methods may be improved, but we do not know the results of these methods. E does not affect the argument.