What adaptation enables leaves at the top a tall pine tree to receive water

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.

Substances that can pass through cell membranes by diffusion include a. na ions. b. proteins c. glucose. d. oxygen.

If people from georgia have just experienced an extremely cold winter the last couple of months, what would the climate most likely be classified as? polar temperate maritime tropical