What would happen if your circulatory system did not deliver oxygen to your blood cells

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

How are viruses different from eukaryotic cells?

What process occurs during cellular development as the cell changes into a specific type of cell with specialized functions? a. binary fission b. fusion c. differentiation d. meiosis