Ap Bio Vocab Chapter 23

Front 1

average heterozygosity

Back 1

the percent, on average, of a population's loci that are heterozygous in members of the population

Front 2

Balanced polymorphism

Back 2

when natural selection maintains stable frequencies of two or more phenotypes in a population

Front 3

balancing selection

Back 3

natural selection that maintains two or more phenotypic forms in a population

Front 4

bottleneck effect

Back 4

genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions

Front 5

cline

Back 5

a graded change in a character along a geographic axis

Front 6

directional selection

Back 6

natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals

Front 7

disruptive selection

Back 7

natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with the intermediate phenotypes.

Front 8

duplication

Back 8

an aberration in chromosome structure due to fusion with a fragment form a homologous chromosome, such that a portion of a chromosome is duplicated

Front 9

fitness

Back 9

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals

Front 10

founder effect

Back 10

genetic drift that occurs when a few individuals become isolated from a large population and form a new population whose gene pool composition is not reflective of that of the original population

Front 11

frequency-dependent selection

Back 11

a decline in the reproductive success of individuals that have a phenotype that has become too common in a population

Front 12

gene flow

Back 12

the transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes

Front 13

gene pool

Back 13

the aggregate of all of the alleles for all of the loci in all individuals in a population

Front 14

genetic drift

Back 14

a process in which change events cause unpredictable fluctuations in alleles frequencie form one generation to the next

Front 15

geographic variation

Back 15

differences between the gene pools of geographically separate populations of population subgroups

Front 16

Hardy-Weinberg equilibrium

Back 16

the condition describing a nonevolving population (one that is in genetic equilibrium)

Front 17

Hardy-Weinberg theorem

Back 17

the principle that frequencies of alleles and genotypes in a population remain constant from generation to generation provided that only Mendelian segregation and recombination of alleles are at work.

Front 18

Heterozygote advantage

Back 18

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

Front 19

Intersexual selection

Back 19

selection whereby individuals of one sex are choosy in selecting their mates from individuals of the other sex

Front 20

intrasexual selection

Back 20

a direct competition among individuals of one sex ually the males in vertebrates for mates of the opposite sex

Front 21

microevolution

Back 21

evolutionary change below the species level; change in he allele frequencies in a population over generations

Front 22

modern synthesis

Back 22

a union of ideas from several biological specialties which provides a widely accepted account of evolution

Front 23

mutation

Back 23

a change in the nucleotide sequence of an organism's DNA, ultimately creating genetic diversity

Front 24

Neutral Variation

Back 24

genetic variation that does not appear to provide a selective advantage or disadvantage

Front 25

Phenotypic Polymorphism

Back 25

selection based solely on an individual's phenotype

Front 26

Population

Back 26

a localized group of individuals of the same species that can interbreed, producing fertile offspring

Front 27

Population genetics

Back 27

the branch of life sciences that studies short- and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes.

Front 28

Pseudogene

Back 28

a DNA segment very similar to a real gene but which does not yield a functional product

Front 29

Relative fitness

Back 29

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population

Front 30

sexual dimorphism

Back 30

marked differences between the secondary sex characteristics of males and females

Front 31

sexual selection

Back 31

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