Which of the following statements describes best the hypothesized steps in the o

Question

Which of the following statements describes best the hypothesized steps in the origin of eukaryotic cells?

a A bacterium integrated the genome of a virus and both evolved as endosymbionts. The plasma membrane folded and surrounded the DNA, forming the nucleus.

b An aerobic bacterium engulfed and digested an anaerobic bacterium, then integrated selected genes into its genome.

c The plasma membrane folds in, surrounds the DNA, and forms the endoplasmic reticulum. An aerobic bacterium is engulfed, but not digested, and then evolves into the mitochondrion.

d Aerobic bacteria engulfed cyanobacteria, which are the ancestors of mitochondria.

Explanation / Answer

c The plasma membrane folds in, surrounds the DNA, and forms the endoplasmic reticulum. An aerobic bacterium is engulfed, but not digested, and then evolves into the mitochondrion.

Serial endosymbiotic theory:

1. The protective cell wall of a prokaryotic cell was lost.

2. Infolding of the plasma membrane increased the surface area.

3. Internal membranes studded with ribosomes (ER) are formed. Some of which surround the nucleus also.

4. Cytoskeleton is formed

5. DNA is attached to the infolded membrane and nucleus precursor is formed.

6. An eukaryotic flagellum is formed enabling propulsion

7. Early digestive vesicles evolved into lysosomes

8. Peroxisomes may have been formed through endocytosis of prokaryotes

9. Mitochondria formed through endocytosis of prokaryotes enabling the production of ATP.

10. endocytosis of a cyanobacterium led to the development of chloroplasts.

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