During meiosis, DNA is exactly copied, and most genetic/allelic combinations on the chromosomes are maintained by the relatively low number of crossing over events, but those crossing over events that do occur produce new genetic combinations among alleles of different genes. This leads to genetic diversity among offspring, fodder for natural selection. Thus, the way that sexual reproduction works among animals provides both some stability for successful parental genotypes but also a reserve of new genetic diversity among offspring in case of changes in the environment, which lead to changes in selective pressures.
Work Step by Step
This question asks you to skim through the chapter and see how meiosis produces genetic variation and how often that occurs. Then, use your imagination to see how this connects to evolution, especially how natural selection acts on genetic diversity to chose new combinations when the environment changes. Consider the benefits of inheritance of selected traits as well as the necessity of the introduction of new traits and combinations.