Answer:Darwin realized that existing heritable variation in a generation must be the starting point for a change in nature. In any generation, the animals in the litter are never quiet the same. And in the wild,such a tiny heritable variation might make all the difference between life and death.
Darwin realized that variation must be the starting point for change in nature. In any generation, the animals in a litter are never quite the same. And in the wild, such a tiny variation might make all the difference between life and death.
