Answer: (A) the time that two species have been evolving independently.
Explanation: The molecular clock is figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when<u> two or more life forms.</u>
I think you're confused. There are only two sexes, male and female. Sex is what you were biologically born as from birth, while gender is what you choose to identify as. Gender is a choice, sex isn't. They couldn't discover any other genders because at the time they probably didn't even know what gender was like three thousand years ago, therefore they couldn't look like a different gender.
The theory would be endosymbiont theory. It was developed on the idea that some eukaryotic organelles come from prokaryotic organisms. It is also known as symbiogenesis. This theory says that these organelles were first from prokaryotic cells that is living inside a host cell.
It is an organelle which helps in appearance of leaf ( color )