Which is a common practice for farmers to yield higher crop production? A) Overplowing mixes the nutrients in the soil
B) consistently plant the same crop every year
C) allow later-successional growth to replace nutrients
D) keep the area planted with early-successional species

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.