A certain species of bird has two basic varieties crested and noncrested. The birds, which generally live in flocks t...

Irina on September 3, 2019

@Marissa-Avnaim,

The argument tells us that there are crested and non-crested birds that usually live in flocks of the same species and select mates of the same variety as themselves, i.e. crested bird picks a crested mate. If the bird is raised in a crested flock and is later moved to a mixed flock, it is likely to select a crested mate regardless of whether the bird itself is crested or uncrested. The argument then concludes that the mate preference is learned rather than genetically determined as the evidence suggests that the bird learns to pick its mate from the other members of the flock, i.e. a non-crested bird in a crested flock sees all the other members picking crested mates and does the same.

The question asks us to identify a statement that would provide the most support for the argument:

(A) Birds of other species also tend to show preferences for mates with certain physical features.

Incorrect. Birds of other species are irrelevant as the argument only concerns a certain species of bird with two basic - crested/ noncrested varieties.

(B) In general there are few behavioral differences between the crested and noncrested birds.

Incorrect. This fact is irrelevant to the conclusion as it fails to demonstrate the basis for selecting a mate.

(C) Both the crested and noncrested birds of the species tend to select mates that are similar in size and age.

Incorrect. This fact merely tells us that the birds tend to select mates of similar size/ age but it fails to explain whether the preference is learned or genetic.

(D) If a crested bird of the species is raised in captivity apart from other birds and is later moved to a mixed block, it is likely to select a crested mate.

Incorrect. This fact weakens the argument because it suggests that the preference is genetic if the bird is raised apart from other birds and had no flock to learn from, but still demonstrates a preference for mates of the same type as itself.

(E) If a bird is raised in a mixed flock, that bird shows no preference of one variety or the other.

Correct. This fact strengthens the argument because it demonstrates that a bird's mate preference is shaped by the flock it is raised in rather than genetically predetermined. In this case, the bird raised in a mixed flock with birds of both crested and non-crested varieties would have no preference in its selection of a mate because mates of both varieties were common in a mixed flock.

Does this make sense?

Let me know if you have any further questions.