Chapter 23

Front 1

population genetics

Back 1

the extensize genetic variation within populations and recognizes thae importance of quantitative characters

Front 2

modern synthesis

Back 2

population as unit of evolution, natural selection most important mechanisms

Front 3

gradualism

Back 3

large changes can evolve as an accumulation of small changes occuring over long periods of time

Front 4

population

Back 4

localized group of individuals belonging to the same species

Front 5

species

Back 5

group of populations whose inidividuals have the potential to interbreed and produce fertile offsrping in nature

Front 6

gene pool

Back 6

total aggregate of genes in a population at any one time. all alleles at all gene loci in all individuals of the population

Front 7

fixed

Back 7

all members of a population are homozygous for the same allele

Front 8

genetic structure

Back 8

populations frequencies of allels and genotypes

Front 9

Hardy Weinberg theorem

Back 9

frequencies of allels and genotypes in a populations gene pool remain constant over the generations unless acted pon by agents other than sexual recombination

Front 10

HW in a nutshell

Back 10

the sexual shufflinf of alleles due to meiosis and random fertilization has no effect on the overall genetic structure of a population

Front 11

Hardy Weinberg Equilibrium

Back 11

meiosis and random fertilization have maintained the same allel and genotype frewuencies that existed in the previous generation

Front 12

Hardy Weinberg equation
p^2 + 2pq + q^2

Back 12

enables us to calculate the frequencies of alleles in a gene pool if we know frewuencies of genotypes and vice versa/

Front 13

microevolution

Back 13

evolution is a generation to generation change in a population's frequencies of alleles or genotypes--a change in a populations genetic structure

Front 14

5 Requirement for hardy weinberg

Back 14

1. large population
2. isolation from other pops.
3. no net mutations
4. random mating
5. no natural selection

Front 15

Genetic Drift

Back 15

changes in the gene pool of a small population due to chance. caused by pop. bottlenecks and founding of new colonies

Front 16

the bottleneck effect

Back 16

by chance, certain allels will be overrepresented among survivors, other alleles will be underrepresented, and some allels may be eliminated completely

Front 17

the founder effect

Back 17

genetic drift in a new colony

Front 18

gene flow

Back 18

genetic exchange due to the migration of fertile individuals or gametes between populations.

Front 19

mutation

Back 19

change in an organism's DNA

Front 20

nonrandom mating

Back 20

individuals usually mate with close neighbors. leads to interbreeding-mating between closely related partners

Front 21

assortive mating

Back 21

individuals select partners that are like themselves in certain phenotypic characters

Front 22

natural selection

Back 22

differential success in reproduction. only one that adapts a population its environment. accumulates and maintains favorable genotypes in a population

Front 23

morphs

Back 23

when two or more forms of a discrete character are represented ina population

Front 24

polymorphic

Back 24

two or more distinct morphs are each represented in high enough frequencies to be readily noticeable

Front 25

measuring genetic variation

Back 25

percentage of gene loci represented by 2+ allels in a population/ average percentage of loci that are heteroz. in individuals of pop

Front 26

geographical variation

Back 26

differences in genetic structure between populations

Front 27

cline

Back 27

graded change in some trait along a geographic axis

Front 28

mutation

Back 28

new alleles originate only by this method, a change in the nucleotide sequence of DNA

Front 29

sexual recombination

Back 29

sex shuffles allels and deals them at random to determine individual genotypes

Front 30

diploidy

Back 30

hides a considerable amount of genetic variation from selection inthe form of recessive allels in heterozygotes. maintain genetic possibilities

Front 31

balanced polymorphism

Back 31

selection itself may preserve variation at some gene loci. ability of natural selection to maintain diversity in a population

Front 32

heterozygous advantage

Back 32

if individuals who are hetoz at a particular locus have greated reproductive success, than any type of homoz, then 2+ allels will be maintained at that locus by natural selection

Front 33

hybrid vigor

Back 33

crossbreeding between 2 diff. inbred varieties often produces hybrids that are much more vigorous than either parent stock

Front 34

frequency dependent selection

Back 34

the reproductive success of any one morph declines if that phenotypic form becomes too common in the population

Front 35

neutral variation

Back 35

seems to confer no selective advantage for some individuals over others. not affected by natural selection

Front 36

darwinian fitness

Back 36

the measure that is critical to selection, is the relative contribution an individual makes to the gene pool of the next generation

Front 37

relative fitness

Back 37

contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus

Front 38

stabilizing selection

Back 38

acts against extreme phenotypes and favors the more common intermediate variants.

Front 39

directional selection

Back 39

shifts the frequency curve for variations in some phenotypic character in one direction of the other by favoring initially rare individuals that deviate from the average for that character

Front 40

diversifying selection

Back 40

environmental conditions are varied in a way that favors individuals on both extremes of a phenotypic range or intermediate phenotypes.

Front 41

sexual dimorphism

Back 41

distinction between the secondary sex characteristics of males and females

Front 42

sexual selection

Back 42

a separate selection process leading to sexual dimorphism

Front 43

natural selection cannot produce perfection because:

Back 43

1. orgs are locked into historical constraints
2. adaptations are often compromises
3. Not all evolution is adaptive
4. selection can only edit variations that exist