Question

Which of the following is true of secondary endosymbiosis?It is indicated by the presence of a double membrane surrounding the endymbiont.An organism containing one endosymbiont engulfs another organism, and that organism becomes an endosymbiont.It is indicated by the presence of a nucleomorph.An organism containing an endosymbiont is engulfed by another organism and becomes an endosymbiont.It is indicated by the presence of a mixotroph.

Answer 1

Secondary endosymbiosis involves an organism with an endosymbiont being engulfed by another organism, leading to complex structures like plastids in chlorarachniophytes, which are surrounded by multiple membranes, including additional ones from the secondary engulfing event.

Step-by-step explanation:

Secondary endosymbiosis occurs when an organism containing an endosymbiont is itself engulfed by another organism, resulting in a coevolutionary relationship. This subsequent endosymbiotic event leads to the presence of additional membranes surrounding the endosymbiont, which includes the engulfing organism's plasma membrane and the original host's phagosomal membrane. A key characteristic of secondary endosymbiosis is the presence of more than two membranes, often three or four, around the plastids - as is the case with chlorarachniophytes, and sometimes a remnant nucleus known as a nucleomorph.

In the case of chlorarachniophytes, a eukaryotic cell engulfed a green alga that had previously engaged in primary endosymbiosis with a cyanobacterium. This subsequent event illustrates secondary endosymbiosis. The plastid within chlorarachniophytes thus has four surrounding membranes, reflecting its complex endosymbiotic history.

Answer 2

The correct answer is: An organism containing an endosymbiont is engulfed by another organism and becomes an endosymbiont.

Primary endosymbiosis - process in which a eukaryotic cell engulfs another living prokaryotic cell

Secondary endosymbiosis –process in which eukaryotic cell engulfs another eukaryote cell that has already undergone primary endosymbiosis.