How does the respiratory system interact with the circulatory system?
group of answer choices

it filters blood that moves through the circulatory system.

it makes blood that is pumped by the circulatory system.

it allows gas exchange between the air and blood.

it to move the blood from the lungs to heart.

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.