What is the function of the primary and secondary pharyngeal bars in Amphioxus?

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.

Amajor source of energy for your body comes from

What nursing actions are part of the acute respiratory distress syndrome clinical network (ardsnet) protocol?