#18 - Concept Reference, Parallel

[Administrator]

Complete Question Explanation

The correct answer choice is (D).

Answer choice (A):

Answer choice (B):

Answer choice (C):

Answer choice (D): This is the correct answer choice.

Answer choice (E):

This explanation is still in progress. Please post any questions below!

[MountainGirl234]

I'm not sure I entirely understand why the correct answer is D over C. I understand the definition of biological species concept to be found in paragraph one in which it is described as "very similar populations of birds into a single species." Later in that paragraph, it is explained that proponents of the biological species concept define a species "as a group that is reproductively isolated from other groups, which means that there is no substantial interbreeding in the wild."

I found this text to match up with C, as D says that the species do interbreed, which seems to conflict with the definition included in the passage.

This is a question that requires textual support and I'm not sure what I'm missing in my evaluation.

[Adam Tyson]

You've identified the right textual support here, MountainGirl234, but it appears that you got the implications of that text backwards. The biological species concept employed by the lumpers would indicate that when two groups do not substantially interbreed, they are not the same species, and so they should be treated as distinct species. Answer C has two groups that are in mutually isolated habitats, which would mean they have no contact with each other and therefore do not interbreed. Our lumpers couldn't lump those groups together based on breeding, so they would have to treat them as separate species. Answer C got that backwards and says they would belong to the same species! That makes it an opposite answer and therefore incorrect.

Meanwhile, in answer D, the two groups interbreed despite their different characteristics, and so the lumpers would lump them together into one species, as that answer says. That's the biological species concept in action!

[gwlsathelp]

I think it's better explained that when the stimulus says that there is no substantial interbreeding between two groups, it means that those two groups are incapable of interbreeding. They are too far away from each other evolutionary to be able to create viable offspring, AKA reproductive isolation. The fact that those two populations do interbreed indicates that they are not reproductively isolated just as the definition for biological species concept specifies. I too selected C) over D), but realize that I interpreted the reproductive isolation to mean literal physically distanced isolation.

[Adam Tyson]

Certainly, complete physical isolation would ensure no interbreeding, gwlsathelp, but that's not required by the definition of the concept given in the passage. If two populations were capable of interbreeding but did not generally do so, the lumpers would treat them as distinct species, while the splitters might call them a single species if they had some traceable common ancestry. The names of the two groups seem a little counterintuitive in that sense - the lumpers are splitting them apart, while the splitters might lump them together.

We have to be careful to stick to what they tell us and take those words at face value. It's not that they cannot interbreed, just that they don't do so. Imagine domestic dogs and wolves, for example: in some cases they can breed, but due perhaps to their social conditions they rarely do. Lumpers would say they are different species, while splitters might, in some cases, put them in one basket.

[justlikemagic]

can someone explain to me maybe their thought process while reading the paragraph because I did not pick up on the implication Adam mentioned with the definitions of how the groups define species. even with his explanation and re-reading the paragraph I'm still confused and of course I want to fully understand why D is the correct answer choice. (I chose C) and at the time I had the same understanding as the person who made the first post. I understand what he said, I'm just not picking that up when I read it, if that makes sense.

thanks

[Robert Carroll]

justlikemagic,

I boiled things down to their basics when I saw those viewpoints in the first paragraph, and that's all you need:

lumpers = biological concept = reproductively isolated

splitters = phylogenetic = pattern of ancestry and descent

The effects of their different views on specific bird species decisions will all have to boil down to how the different viewpoints are defined starting in the middle of the paragraph. I think you and the first post here are getting too caught up with how these viewpoints get applied in bird cases. That information is useful, but cannot possibly change the way the author has defined the groups later in the paragraph, which is why I focused so much on those viewpoint definitions, as they are clear expressions of what matters to each group.

In short, for this question, interbreeding = same species for the biological concept. Reproductively isolated = different species. That is all the information needed to answer this question.

Robert Carroll

[sabinarose99]

Can someone please help me with this? I've read all the above explanations and this answer D seems to completely contradict with the first paragraph. P1 states that the biological species concept defines "a species as a group..." where there is "no substantial interbreeding" while answer D says "they interbreed..." so they should be considered the "same species." How do these two ideas not contradict each other?

[katehos]

Hi sabinarose99!

Good job pointing out the location of the textual support! According to paragraph 1, the species concept delineates between unique species based on reproductive capability. In this view, members of a particular species do not substantially interbreed with other groups in the wild. So, we also know that if the groups do substantially interbreed, then they're members of the same species. With this understanding in mind, we can see how (D) is correct.

In answer choice (D), two populations interbreed, so they're the same species! This aligns perfectly with our understanding of the species concept described in the first paragraph. I definitely see where your confusion stems from, but hopefully this helps illustrate that those two things are not contradictory, but rather, are perfectly in line with one another (almost like a contrapositive)!

I hope this helps
Kate