Bio 202 Ch 20 And 21 Vocab - Test One

Front 1

Natural selection

Back 1

the differential reproduction of genotypes; caused by factors in the environment; leads to evolutionary change

Front 2

Hardy-Weinberg equilibrium

Back 2

mathematical description of the fact that allele and genotype frequencies remain constant in a random-mating population in the absence of inbreeding, selection, or other evolutionary forces

Front 3

Gene Flow

Back 3

movement of alleles from one population to another

Front 4

Assortative mating

Back 4

a type of nonrandom mating in which phenotypically similar individuals mate more frequently

Front 5

Disassortative mating

Back 5

a type of nonrandom mating in which phenotypically different individuals mate more frequently

Front 6

Genetic drift

Back 6

random fluctuation in allele frequencies over time by chance

Front 7

Founder effect

Back 7

the effect by which rare alleles and combinations of alleles may be enhanced in new populations

Front 8

Bottleneck effect

Back 8

a loss of genetic variability that occurs when a population is reduced drastically in size

Front 9

Artificial selection

Back 9

change in the genetic structure of populations due to selective breeding by humans

Front 10

Fitness

Back 10

the genetic contribution of an individual to succeeding generations

Front 11

Frequency-dependent selection

Back 11

a type of selection that depends on how frequently or infrequently a phenotype occurs in the population

Front 12

Oscillating selection

Back 12

the situation in which selection alternately favors one phenotype at one time, and a different phenotype at another time, for example, during drought conditions versus during wet conditions

Front 13

Heterozygote advantage

Back 13

the situation in which individuals heterozygous fora trait have a selective advantage over those who are homozygous; example- sickle cell anemia

Front 14

Disruptive selection

Back 14

a form of selection in which selection acts to eliminate rather than favor the intermediate type

Front 15

Directional selection

Back 15

a form of selection in which selection acts to eliminate one extreme from an array of phenotypes

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Stabilizing selection

Back 16

a form of selection in which selection acts to eliminate both extremes from a range of phenotypes

Front 17

Relative dating

Back 17

the determining the relative order of past events, without necessarily determining their absolute age

Front 18

Absolute dating

Back 18

age of fossils is estimated by rates of radioactive decay

Front 19

Homologous structures

Back 19

structures with different appearances and functions that all derived from the same body part in a common ancestor

Front 20

Vestigial structures

Back 20

a morphological feature that has no apparent current function and is thought to be an evolutionary relic; example: hip bones in boa constrictors

Front 21

Convergent evolution

Back 21

the independent development of similar structures in organisms that are not directly related

Front 22

Genotype

Back 22

the genetic makeup of an organism

Front 23

Phenotype

Back 23

the visible expression of a gene, the observable characteristics of an individual

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Allele

Back 24

one of two alternative states of a gene

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Species

Back 25

a kind of organism; designated by binomial names written in italics

Front 26

Negative frequency-dependent selection

Back 26

rare phenotypes are favored by selection; maintains variation

Front 27

Positive frequency-dependent selection

Back 27

common phenotypes are favored; variation is eliminated from the population