evolution of population

Question 1

a localized group of individuals capable of interbreeding and producing fertile offspring

Answer 1

population

Question 2

change in allele frequencies in a population over generations

Answer 2

microevolution

Question 3

three mechanisms cause allele frequencies change:

Answer 3

-natural selection
-genetic drift (chance events that alter allele frequencies)
-gene flow (the transfer of alleles between populations)

Question 4

differences among individuals in the composition of their genes or other DNA sequences

Answer 4

genetic variation

Question 5

the product of inherited genotype and environmental influences

Answer 5

phenotype

Question 6

can only act on variation with a genetic component

Answer 6

natural selection

Question 7

can be classified on an either-or basis

Answer 7

discrete characters

Question 8

vary along an continuum within a population

Answer 8

quantitative characters

Question 9

measures the average percent of loci that are heterozygous in a population

Answer 9

average heterozygosity

Question 10

measured by comparing the DNA sequences of pairs of individuals

Answer 10

nucleotide variability

Question 11

a change in the nucleotide sequence of an organism’s DNA

Answer 11

mutation

Question 12

differences between gene pools of separate populations

Answer 12

geographic variation

Question 13

graded change in a trait along a geographic axis

Answer 13

cline

Question 14

consists of all the alleles for all loci in a population

Answer 14

gene pool

Question 15

fixed if all individuals in a population are homozygous for the same allele

Answer 15

locus

Question 16

states the frequencies of alleles and genotype in a population remain constant from generation to generation

Answer 16

Hardy-Weinberg principle

Question 17

The five conditions for nonevolving populations are rarely met in nature:

Answer 17

-No mutations
-Random mating
-No natural selection
-Extremely large population size
-No gene flow

Question 18

describes how allele frequencies fluctuate unpredictably from on generation to the next

Answer 18

genetic drift

Question 19

occurs when a few individuals become isolate from a larger population

Answer 19

founder effect

Question 20

is a sudden reduction in population size due to a change in the environment

Answer 20

bottleneck effect

Question 21

effects of genetic drift: a summary

Answer 21

-significant in small populations
-causes allele frequencies to change at random
-can lead to a loss of genetic variation w/in populations
-can cause harmful alleles to become fixed

Question 22

consists of the movement of alleles among populations

Answer 22

gene flow

Question 23

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

Answer 23

relative fitness

Question 24

favors individuals at one end of the phenotypic range

Answer 24

directional selection

Question 25

favors individuals at both extremes of the phenotypic range

Answer 25

disruptive selection

Question 26

favors intermediate variants and acts against extreme phenotypes

Answer 26

stabilizing selection

Question 27

natural selection for mating success

Answer 27

sexual selection

Question 28

marked differences between the sexes in secondary sexual characteristics

Answer 28

sexual dimorphism

Question 29

is a competition among individuals of one sex (often males) for mates of the opposite sex

Answer 29

intrasexual selection

Question 30

often called mate choice, occurs when individuals of one sex (usually females) are choosy in selecting their mates

Answer 30

intersexual selection

Question 31

is genetic variation that does not confer a selective advantage or disadvantage

Answer 31

neutral variation

Question 32

occurs when natural selection maintains stable frequencies of 2+ phenotypic forms in a population

Answer 32

balancing selection

Question 33

when heterozygotes have a higher fitness than do both homozygotes

Answer 33

heterozygote advantage

Question 34

the fitness of a phenotype declines if it becomes too common int he population

Answer 34

frequency- dependent selection

Question 35

why natural selection cannot fashion perfect organisms

Answer 35

-selection can act only on existing variations -evolution is limited historical constraints -adaptations are often compromises -chance, natural selection, and the environment interact