Biology 182 Chapter 23

Front 1

Change in allele frequencies in a population over generations.

Back 1

Microevolution

Front 2

A heritible feature that can be classified as either or. Ie. Mendel's pea plants were either purple or white.

Back 2

Discreet

Front 3

A heritible feature that varies continuously over a range rather than either-or fashion.

Back 3

Quantitative

Front 4

Having 2 identical allels for a given gene.

Back 4

Homozygous

Front 5

Having 2 different allels for a given gene.

Back 5

Heterozygous

Front 6

Greater reproductive success of heterzyygous individuals compared with homozygotes; tends to preserve variation in a gene pool.

Back 6

Heterozygote Advantage

Front 7

The average percent of loci that are heterozygous.

Back 7

Average Heterozygosity

Front 8

Differences in the genetic composition of populations separated by mountains or other geographic barriers.

Back 8

Geographic Variation

Front 9

A change in the nucleotide sequence of an organism's DNA.

Back 9

Mutations

Front 10

A group of individuals of the same species that live in the same area and interbreed producing fertile offspring.

Back 10

Population

Front 11

Consists of all the alleles for all the loci in all individuals in the population.

Back 11

Gene Pool

Front 12

To determine whether a population is evolving or not by concidering what the population would look like had it not evolved.

Back 12

Hardy-Weinberg Principal

Front 13

This principle states that the frequencies of alleles and genotyoes in a population will remain constant from generation to generation provided that only Mendelion segregation and recombination of alleles are at work.

Back 13

Hardy-Weinberg Equalibrium

Front 14

Chance events can cause allele frequencies to fluctuate unpredictably from one gereration to the next, especially in small populations.

Back 14

Genetic Drift

Front 15

A sudden change in the environment, such as fire or flood, that drastically reduces the size of a population.

Back 15

Bottleneck Effect

Front 16

When a few individuals become isolated from a larger population, this smaller group may establish a new poopulation whose gene pool differs from the source population.

Back 16

Founder Effect
Example: Amish people.

Front 17

The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.

Back 17

Gene Flow

Front 18

The contribution one makes to a gene pool of the next generation , relative to the contributions of other individuals.

Back 18

Relative Fitness

Front 19

Occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting the frequency curve for the phenotypic character in one direction or the other.

Back 19

Directional Selection
Example: Dark mice are favored because they live near dark rocks.

Front 20

Occurs when conditions favor individuals at both extremes of a phynotypic range over individuals with intermediate phynotypes.

Back 20

Disruptive Selection:
Example: Mice that have colonized in a habitat made up of light and dark rocks have an advantage over medium colored mice.

Front 21

Acts against both extreme phenotypes and favors the intermediate variant.

Back 21

Stabilizing Selection

Front 22

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

Back 22

Sexual Selection

Front 23

Marked differences between the two sexes in secondary sexual characteristics, which are not directly associated with reproduction or survival.

Back 23

Sexual Dimorphism
Example: Brightly colored peacocks and dull peahens.

Front 24

Individuals of one sex compete directly for a mate of the opposite sex. Usually males compete with other males and the stronger male wins.

Back 24

Intrasexual Selection

Front 25

Mate Choice. Individuals of one sex (usually female) are choosy in selecting their mates from the other sex.

Back 25

Intersexual Selection

Front 26

The fitness of a phynotype declines if it becomes too common in the population.

Back 26

Frequency-Dependent Selection
Example: Right-Mouthed Fish

Front 27

Nucleotide differences in noncoding sequences appear to confer no selective advantage of disadvantage.

Back 27

Neutral Variation

Front 28

Why does Natural Selection not result in a perfect organism?

Back 28

1) Selection can act only on existing variations. 2) Evolution is limited by ancestory. 3) Adaptations are often compromises.4) Chance, natural selection and environment interact.