AP BIOLOGY

Detailed explanation-1: -Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.

Detailed explanation-2: -In order for natural selection to operate on a trait, the trait must possess heritable variation and must confer an advantage in the competition for resources. If one of these requirements does not occur, then the trait does not experience natural selection.

Detailed explanation-3: -The essence of Darwin’s theory is that natural selection will occur if three conditions are met. These conditions, highlighted in bold above, are a struggle for existence, variation and inheritance. These are said to be the necessary and sufficient conditions for natural selection to occur.

Detailed explanation-4: -There are four principles at work in evolution-variation, inheritance, selection and time. These are considered the components of the evolutionary mechanism of natural selection.

Detailed explanation-5: -Natural selection requires variation between individuals. Mutations and sexual reproduction increase genetic variation in a population. Natural selection occurs when environmental pressures favor certain traits that are passed on to offspring.