Assume that some members of an aquatic species of motile, photosynthetic protists evolve to become parasitic to fish. They gain the ability to live in the fish gut, absorbing nutrients as the fish digests food. Over time, which of the following phenotypic changes would you expect to observe in this population of protists?
A) loss of motility
B) loss of chloroplasts
C) gain of a rigid cell wall
D) gain of meiosis
E) No changes would be expected.

Question

Quizplus · Accepted Answer

Since the protists have adapted to living in the fish gut, they no longer require chloroplasts for photosynthesis as they can obtain their nutrients from the fish's digested food. Therefore, the loss of chloroplasts would be a likely phenotypic change. The loss of motility might also be possible, as it is not necessary for parasites to move actively to obtain nutrients. However, there is no reason to expect the gain of a rigid cell wall or meiosis, nor is it likely that there would be no changes at all.

Assume That Some Members of an Aquatic Species of Motile