Answer:
Originally, the distinction was based on morphological differences. However, it soon became that some types of organisms had different forms at various stages in their lives, here is why
Explanation:
changed genes is passed on to the next generation. Most mutations are bad, but some of them make the organism more successful in its life. Organisms that inherit that favorable new gene are likely to become more abundant than others of the species. (geologic times)
I believe the answer in the blank should be protostar
Answer: Natural selection is one of the forces of evolution and the enviroment where the species lives is the selection agent. For example, suppose a mosquitoes population in a environment free from insecticides, in this environment there's a high frequency of non-resistant mosquitoes because the environment is not exerting any pressure on the resistence trait. But when the environment changes and we use a insecticide upon the mosquitoes population, the populations changes because the non-resistant ones die but those resistant survive and beggin to reproduce more effectively. That's natural selection, differences in survival and reproduction between individuals with different phenotypes (traits) and this differences depend of environmental changes.
Isogametes because they have the same size and shape.