Ch 23

Question 1

microevolution

Answer 1

evolutionary changes in a population, the smallest scale of evolution

Question 2

Microevolution occurs when there are changes in:

Answer 2

allele frequencies

Question 3

Main mechanisms for allele frequency changes

Answer 3

1. natural selection
2. genetic drift
3. gene flow

Question 4

genetic variation

Answer 4

genetic differences among individuals

Question 5

discrete characters

Answer 5

possibilities are either/or

Question 6

quantitative characters

Answer 6

possibilities vary along a continuum

Question 7

average heterozygosity

Answer 7

average percentage of loci that are heterozygous

alt: average percentage of population that are heterozygous for specific loci

Question 8

geographic variation

Answer 8

genetic differences between separate populations

Question 9

cline

Answer 9

graded change in a character along a geographic axis

Question 10

population

Answer 10

individuals of the same species in the same area

Question 11

gene pool

Answer 11

population’s genetic makeup

Question 12

The gene pool contains:

Answer 12

all copies of
all alleles in
all members of a population

Question 13

The Hardy-Weinburg principle describes:

Answer 13

the gene pool of a population that is not evolving

Question 14

Hardy-Weinburg equation for two alleles

Answer 14

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

Question 15

In the equation, p and q =

Answer 15

frequency of an allele

Question 16

In the equation, p^2 and q^2 =

Answer 16

frequency of a genotype

Question 17

Conditions for Hardy-Weinburg

Answer 17

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

Question 18

genetic drift

Answer 18

chance events cause unpredictable fluctuation in allele frequencies

Question 19

Genetic drift has a greater effect on:

Answer 19

small populations

Question 20

Two types of genetic drift:

Answer 20

founder and bottleneck effects

Question 21

founder effect

Answer 21

when a few individuals become isolated and establish a new population whose gene pool differs from the source population

Question 22

bottleneck effect

Answer 22

severe drop in population sizes that causes over-/underrepresentation or loss of alleles

Question 23

gene flow

Answer 23

transfer of alleles into or out of population

Question 24

Natural selection is the only mechanism that:

Answer 24

consistently causes adaptive evolution

Question 25

adaptive evolution

Answer 25

betters match between the organism and the environment

Question 26

relative fitness

Answer 26

contribution an individual makes to the gene pool of the next generation relative to others’ contributions

Question 27

Types of selection

Answer 27

1. directional
2. disruptive
3. stabilizing

Question 28

directional selection

Answer 28

favors one extreme of a phenotypic range

Question 29

disruptive selection

Answer 29

favors both extremes of a phenotypic range

Question 30

stabilizing selection

Answer 30

favors intermediate variants of a phenotypic range

Question 31

sexual selection

Answer 31

individuals with certain inherited traits are more likely to obtain mates

Question 32

balancing selection

Answer 32

when natural selection maintains two or more forms in a population

Question 33

heterozygote advantage

Answer 33

being heterozygous at a particular locus makes the organism best fit

Question 34

frequency-dependent selection

Answer 34

fitness of a phenotype depends on how common it is in the population

Question 35

Why don’t organisms become perfect through selection?

Answer 35

1. selection only acts on existing variation
2. limited by historical anatomy
3. adaptations are often compromises
4. chance and environment