Chapter 23 Campbell Reece

Front 1

Population

Back 1

a localized group of individuals that can interbreed and produce fertile offspring

Front 2

Gene Pool

Back 2

all the genes in a population

Front 3

Population Genetics

Back 3

the study of how populations change genetically over time

Front 4

Allele

Back 4

alternative versions of the same gene

Front 5

Allele Frequency

Back 5

Each allele has a frequency in a population

Front 6

Harvey-Weinberg Theorem

Back 6

the genotype frequencies at a single gene locus will become fixed at a particular equilibrium value

Front 7

Conditions - Harvey-Weinberg
"Not evolving"

Back 7

1. extremely large population size
2. no gene flow
3. no mutations in alleles being studied
4. no random mating among the population
5. no natural selection

Front 8

Harvey-Weinberg Equilibrium

Back 8

p2 + 2pq + q2 = 1

Front 9

Causes of Evolution

Back 9

1. Mutation
2. Sexual recombination
3. Natural Selection
4. Genetic Drift
5. Gene Flow

Front 10

Mutation

Back 10

Change in the DNA sequence of a gene
1 in 100,000

Front 11

Sexual recombination

Back 11

Crossing over (Chiasmata)
homologous chromosomes

Front 12

Natural selection

Back 12

If a gene confers a selective advantage on its bearer, than that bearer will produce more offspring

Front 13

Genetic drift

Back 13

unpredictable fluctations in allele frequency from one generation to the next

Front 14

Bottleneck effect

Back 14

dramatic reduction in the size of a population leaves only a few survivors. Decrease in variation due to significantly smaller gene pool

Front 15

Founder effect

Back 15

small group is isolated from a larger population and establishes a new population.
Decrease in variation due to significantly smaller gene pool

Front 16

Gene flow

Back 16

genetic additions or subtractions to or from a population. movement of fertile individuals or gametes. Reduces genetic difference in Populations

Front 17

Fitness

Back 17

the contribution an individual makes to the gene pool of the next generation

Front 18

Relative fitness

Back 18

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

Front 19

Directional selection

Back 19

favors variants at one extreme of a distribution

Front 20

Disruptive selection

Back 20

favors individuals on both extremes of a phenotypic range over intermediate phenotypes

Front 21

Stabilizing selection

Back 21

favors intermediate variants and acts against extreme phenotypes

Front 22

Diploidy

Back 22

Heterozygosity provides protection for destructive recessive alleles

Front 23

Heterozygote advantage

Back 23

heterozygotes for a particular trait have greater overall fitness over homozygotes.
Example: Sickle-cell anemia

Front 24

Frequency-dependent selection

Back 24

fitness of a phenotype declines as it becomes too common in a population

Front 25

Neutral Variation

Back 25

Genes that have no impact on reproductive success are not affected by natural selection.

Front 26

Sexual selection

Back 26

Natural selection relies on reproductive success. Sexual selection can result in “bad genes” being propagated over generations.

Front 27

Why not PERFECT organisms??

Back 27

1. Evolution is limited by history
2. Adaptations are often compromises
3. Chance and natural selection interact
4. Selection can only edit existing variations – new alleles cannot arise on demand

Front 28

Reproductive handicap

Back 28

sexual reproduction produces fewer offspring than asexual reproduction

Front 29

Aide in disease resistance

Back 29

sexual reproduction

Front 30

Intrasexual selection

Back 30

competition among individuals of one sex for mates of the opposite sex

Front 31

Intersexual selection

Back 31

individuals of one sex are choosy in selecting their mates

Front 32

sexual dimorphism

Back 32

marked differences between the sexes in secondary sexual characteristics

Front 33

Microevolution

Back 33

change in genetic makeup of a population from one generation to the next

Front 34

The modern synthesis

Back 34

Poulations as units of evolution

Population genetics integrates Mendelian genetics with Darwin's Theory of Evolution

Front 35

Point mutation

Back 35

change in one base in a gene, could be harmless or fatal

Front 36

Polymorphism

Back 36

two or more distinct morphs for a characteristic are represented in a high frequency

Front 37

Genetic variation _ heterozygosity

Back 37

Average percentage of loci that are heterozygous

Front 38

Discrete characters

Back 38

either-or basis

Front 39

Quantitative

Back 39

vary along a continuum

Front 40

Cline

Back 40

graded change in a trait along a geographic axis