The correct answer is it decreases genetic diversity only by reducing population size.
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The great explanation for this is a bottleneck effect, which is an extreme example of genetic drift. The bottleneck effect occurs when the size of a population is reduced due to a catastrophe. When it happens, only a small, random number of individuals survive the event and pass through the bottleneck. Thus, the genetic composition of the random survivors is now the genetic composition of the entire population which means that the genetic diversity is reduced.</span>
There is quite a lot, but the fact that both mitochondria and chloroplasts have their own circular DNAis what I would call "key" evidence. That is, these organelles are not "manufactured" by the cell (i.e., there are no "genes for mitochondria" in eukaryote genomes): like their ancestral bacteria, they reproduce by binary fission.
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Related questions (More answers below)
Once you finish
growing to adulthood, neurons stop dividing. Hair follicle cells constantly
divide throughout your lifetime since they are constantly producing cells that
become part of the hair itself as they die. So in an adult, the rate of cell
division for neurons is zero (although there is some counter-evidence but it is
certainly very low) while the hair follicle rate is much higher on the order of
once every few days or faster.
