Question

1. in humans, nearly all of the mitochondria originate from the ______________
2. what observation led to the endosymbiotic theory?

____________________________________________________

Explanation:

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In human reproduction, the egg (ovum) contributes nearly all the mitochondria to the zygote. Sperm mitochondria are usually degraded after fertilization. So the mitochondria in humans nearly all originate from the mother (specifically the maternal egg/ovum).

The endosymbiotic theory proposes that eukaryotic organelles like mitochondria and chloroplasts originated from prokaryotic organisms that were engulfed by a host cell. Key observations include: Mitochondria and chloroplasts have their own circular DNA (similar to prokaryotic DNA), they have their own ribosomes (similar in size to prokaryotic ribosomes), they reproduce independently within the cell (by binary fission, like prokaryotes), and they have a double - membrane structure (the outer membrane may be from the host cell's vesicle and the inner membrane from the original prokaryote). Also, the size of mitochondria and chloroplasts is similar to that of prokaryotes.

Answer:

mother (maternal egg/ovum)

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