AP BIOLOGY

Detailed explanation-1: -Natural selection occurs when one allele (or combination of alleles of different genes) makes an organism more or less fit, that is, able to survive and reproduce in a given environment.

Detailed explanation-2: -Evolution by mutation occurs whenever a mistake in the DNA occurs in the heritable cells of an organism. In the single-celled asexual organisms, such as bacterial, the whole cell and its DNA is passed on to the next generation because these organisms reproduce via binary fission.

Detailed explanation-3: -Natural selection is considered the main mechanism that causes populations to evolve. However, there are several other mechanisms of evolution, including mutation, genetic drift, and gene flow.

Detailed explanation-4: -Mutations are essential to evolution. Every genetic feature in every organism was, initially, the result of a mutation. The new genetic variant (allele) spreads via reproduction, and differential reproduction is a defining aspect of evolution.

Detailed explanation-5: -Although natural selection is the mechanism of evolution most commonly discussed, other evolutionary mechanisms also change the frequencies of traits (and the genes that control them) in populations. These include mutation, genetic drift and migration.