Theoretically, P.bursaria can obtain zoochlorella either vertically (via the asexual reproduction of its mother cell)or horizontally (by ingesting free-living Chlorella from its habitat). Consider a P. bursaria cell containing zoochlorellae, but whose habitat lacks free-living Chlorella. If this cell subsequently undergoes many generations of asexual reproduction, if all of its daughter cells contain roughly the same number of zoochlorellae as it had originally contained, and if the zoochlorellae are all haploid and identical in appearance, then what is True?
A)The zoochlorellae also reproduced asexually, at an increasing rate over time.
B)The zoochlorellae also reproduced asexually, at a decreasing rate over time.
C)The zoochlorellae also reproduced asexually, at a fairly constant rate over time.
D)The zoochlorellae reproduced sexually, undergoing heteromorphic alternation of generations.
E)The zoochlorellae reproduced sexually, undergoing isomorphic alternation of generations.

Question

Quizplus · Accepted Answer

Since the habitat lacks free-living Chlorella, the only possible source of zoochlorella in the daughter cells is vertical transmission via asexual reproduction. If the daughter cells contain roughly the same number of zoochlorellae as the original cell, this implies that the zoochlorellae are also being transmitted to daughter cells at a fairly constant rate. Therefore, the most likely scenario is that the zoochlorellae are reproducing asexually at a fairly constant rate over time. Choices A and B are not supported by the information given in the question, and choices D and E involve sexual reproduction, which is not mentioned as a possibility for the zoochlorellae.