Question

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gather at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae. Theoretically, P. bursaria can obtain zoochlorellae 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 which statement is accurate?

Answer 1

Answer:

Zoochlorellae also reproduced asexually at a nearly constant rate

Explanation:

Zoochlorellae (singular Zoochlorella), also referred to as Chlorella-like algae, is a genus of algae that live inside freshwater protozoans (e.g., Paramecium bursaria), exhibiting a symbiotic association with their hosts. Asexual reproduction is a type of reproduction that produces new individuals without the fusion of gametes and does not involve a change in the number of chromosomes. In consequence, a haploid parent, i.e., an individual who contains a single set (n) of chromosomes, will produce haploid (n) offspring. Moreover, and since the question indicates that daughter cells contain approximately the same number of zoochlorellae cells as parent cells, it is expected to observe an asexual reproduction rate at a fairly constant rate over time.