Question

Endosymbiosis is an evolutionary theory that explains the origin of eukaryotes and suggests a specific order in which this might have occurred. Ancestral cells engulfed and then began to use the metabolic processes of the smaller cells. Based on shared-core processes and features, which statement most accurately describes the order, the theory, and the evolutionary implications for all organisms within domain Eukarya

Answer 1

The question is incomplete as it lacks multiple options. The options are as follows:

a) Ancestral heterotrophic eukaryotes most likely engulfed both a heterotrophic and an autotrophic prokaryote, whereas ancestral photosynthetic eukaryotes probably provided the host cell for the first mitochondria. Over time, natural selection favored these relationships and these cells became ancestors of all eukaryotes.

b) All ancestral eukaryotes would have most likely consumed a nucleus-like prokaryote that eventually became the eukaryotic nucleus. These new eukaryotic cells would have had an advantage over prokaryotic cells by acquiring a nuclear command center for regulating cellular activities.

c) As carbon dioxide levels were increasing over time, natural selection would have favored organisms that acquired a photosynthetic prokaryote to convert carbon dioxide into sugars. These would have likely been the first eukaryotic cells. At which point, these ancestral cells engulfed mitochondria-like prokaryotes that would have provided an even greater advantage for cells in this environment.

d) As Earth was becoming more aerobic, mitochondria would have provided an advantage to host cells by converting "toxic" oxygen into energy for heterotrophic cells. Since mitochondria are found in all eukaryotes, these combinations likely evolved first. Photosynthetic eukaryotes probably acquired an autotrophic prokaryote, which developed an advantageous symbiotic relationship with the host cell.

Answer:

Option (d).

Explanation:

The endosymbiosis theory explain the evolution of the eukaryotic organisms and its organelle from the prokaryotic organism. This theory explain the mitochondria and chloroplast origin from the free living prokaryotes.

The earth's primitive environment was highly reducing and anaerobic. The oxygen starts evolving in the environment and evolution of mitochondria is beneficial as oxygen can be used for the energy generation. The choloroplast has been evolved from the photosynthetic prokaryotes.

Thus, the correct answer is option (d).

Answer 2

Answer:

Day by day the environment of the earth is becoming more aerobic.

The mitochondria will provided energy for the heterotrophic cells. The advantage of the cell is that it will convert oxygen into energy.

As mitochondria is found in all the eukaryotic cells they evolved first. The photosynthetic eukaryotes acquire autotrophic prokaryotes which is an example of symbiotic relationship.

In this case one cell incorporates itself inside the another cell and function combinely.