Chapter 23: population evolution

Question 1

microevolution

Answer 1

change in allele frequencies in a population over generations

Question 2

average heterozygosity

Answer 2

average percentage of heterozygous loci

Question 3

geographic variation

Answer 3

differences in genetic composition of separate populations

Question 4

cline

Answer 4

graded change in character along a geographic axis

Question 5

gene pool

Answer 5

all copies of every allele at every locus in all members of a population

Question 6

fixed allele

Answer 6

when only one allele exists for a certain locus in a population

Question 7

Hardy-Weinberg Principle

Answer 7

frequencies of alleles and genotypes will remain constant in a population where only Mendelian segregation and recombination of alleles are at work

Question 8

Hardy-Weinberg equation

Answer 8

p^2 + 2pq + q^2 = 1

Question 9

Hardy-Weinberg equilibrium

Answer 9

1. no mutations
2. random mating
3. no natural selection
4. large population size
5. no gene flow

Question 10

adaptive evolution

Answer 10

evolution that results in better match between organisms and their environment

Question 11

genetic drift

Answer 11

process where allele frequencies fluctuate in generations

Question 12

founder effect

Answer 12

a few individuals become isolated from a larger group and their gene pool differs from source population

Question 13

bottleneck effect

Answer 13

severe drop in population size; certain alleles overexpressed in survivors

Question 14

effects of genetic drift

Answer 14

1. significant in small populations
2. cause allele frequencies to change randomly
3. loss of genetic variation in populations
4. harmful alleles can become fixed

Question 15

gene flow

Answer 15

transfer of alleles into or out of population

Question 16

relative fitness

Answer 16

contribution individual makes to gene pool of next generation relative to other individuals

Question 17

directional selection

Answer 17

conditions favor one extreme phenotype

Question 18

disruptive selection

Answer 18

favor phenotypes at both extreme ends

Question 19

stabilizing selection

Answer 19

favors intermediate variatns

Question 20

sexual selection

Answer 20

individuals with certain inherited characteristics more likely to reproduce

Question 21

sexual dimorphisms

Answer 21

differences between sexes and secondary sexual characteristics

Question 22

intrasexual selection

Answer 22

same sex individuals compete for mate

Question 23

intersexual selection

Answer 23

mate choice. one sex is choosy in selecting mates of the other sex

Question 24

neutral variation

Answer 24

differences in DNA that do not offer selective advantage or disadvantage

Question 25

balancing selection

Answer 25

natural selection maintains 2+ forms in a population

Question 26

heterozygote advantage

Answer 26

heterozygous individuals of a locus have greater fitness than homozygotes

Question 27

frequency-dependent selection

Answer 27

fitness of phenotype depends on how common it is in population