The main function of the digestive system is to break food down into molecules that can be absorbed by cells. How are the food molecules absorbed into the cells to start the cellular respiration process? A.
Food molecules are broken down by oxidation and then released by cells.

B.
Food molecules are released into the cells by the respiration process.

C.
Food molecules are absorbed through the cell wall.

D.
Food molecules are absorbed through the cell membrane.

10. in which phase will crossing-over occur? a. mitosis b. metaphase ii c. prophase i d. meiosis ii

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.

What are 3 reasons that natural selection occurs