Chapter 8

Front 1

Allelic frequency

Back 1

is the proportion in which it is present in a population relative to the other alleles of the same gene

Front 2

Evolution

Back 2

is a change in the allele frequencies of a population over time.

Front 3

Natural selection

Back 3

a change in allele frequencies that occurs when individuals with one version of a heritable trait have greater reproductive success than individuals with a different version of the trait, also occurs when the following three conditions are satisfied

-variation for a trait

-heritability

- differential reproductive success

Front 4

Directional selection

Back 4

the average value for the trait increases or decreases

Front 5

Disruptive selection

Back 5

the average value of a trait remains the same while extreme versions of the trait are selected against

Front 6

Stabilizing selection

Back 6

individuals with extreme phenotypes have the highest fitness

Front 7

Mutation

Back 7

alteration of the base-pair sequence in an individuals DNA that changes an alleles frequency

Front 8

Genetic drift

Back 8

is a random change in the allele frequencies within a population, unrelated to any alleles influence on reproductive success

Front 9

Migration

Back 9

or gene flow, a change in allele frequencies caused by individuals moving into or out of a population

Front 10

Founder effect

Back 10

the founding members of a new population can have different allele frequencies than the original source population

Front 11

Bottleneck effect

Back 11

the surviving members of a catastrophic event can have different allele frequencies than the source population

Front 12

Fitness

Back 12

is a measure of the relative amount of reproduction of an individual with a particular phenotype, as compared with the reproductive output of individuals with alternative phenotypes. An individuals fitness can vary, depending on the environment in which the individual lives

Front 13

Adaptation

Back 13

both the process by which the organisms in a population become better matched to their environment and the specific features that make an organism more fit- occurs as a result of natural selection

Front 14

Variation

Front 15

Microevolution

Back 15

a slight change in allele frequencies over one or a few generations

Front 16

Macroevolution

Back 16

the accumulated effect of microevolution over a long period of time