ch. 19

Question 1

adaptive evolution

Answer 1

increase in frequency of beneficial alleles and decrease in deleterious alleles due to selection

Question 2

allele frequency

Answer 2

(also, gene frequency) rate at which a specific allele appears within a population

Question 3

assortative mating

Answer 3

when individuals tend to mate with those who are phenotypically similar to themselves

Question 4

bottleneck effect

Answer 4

magnification of genetic drift as a result of natural events or catastrophes

Question 5

cline

Answer 5

gradual geographic variation across an ecological gradient

Question 6

directional selection

Answer 6

selection that favors phenotypes at one end of the spectrum of existing variation

Question 7

diversifying selection

Answer 7

selection that favors two or more distinct phenotypes

Question 8

evolutionary fitness

Answer 8

(also, Darwinian fitness) individual’s ability to survive and reproduce

Question 9

founder effect

Answer 9

event that initiates an allele frequency change in part of the population, which is not typical of the original population

Question 10

frequency-dependent selection

Answer 10

selection that favors phenotypes that are either common (positive frequencydependent selection) or rare (negative frequencydependent selection)

Question 11

gene flow

Answer 11

flow of alleles in and out of a population due to the individual or gamete migration

Question 12

gene pool

Answer 12

all the alleles that the individuals in the population carry

Question 13

genetic drift

Answer 13

effect of chance on a population’s gene pool

Question 14

genetic structure

Answer 14

distribution of the different possible genotypes in a population

Question 15

genetic variance

Answer 15

diversity of alleles and genotypes in a population

Question 16

geographical variation

Answer 16

differences in the phenotypic variation between populations that are separated geographically

Question 17

good genes hypothesis

Answer 17

theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease

Question 18

handicap principle

Answer 18

theory of sexual selection that argues only the fittest individuals can afford costly traits

Question 19

heritability

Answer 19

fraction of population variation that can be attributed to its genetic variance

Question 20

honest signal

Answer 20

trait that gives a truthful impression of an individual’s fitness

Question 21

inbreeding

Answer 21

mating of closely related individuals

Question 22

inbreeding depression

Answer 22

increase in abnormalities and disease in inbreeding populations

Question 23

macroevolution

Answer 23

broader scale evolutionary changes that scientists see over paleontological time

Question 24

microevolution

Answer 24

changes in a population’s genetic structure

Question 25

modern synthesis

Answer 25

overarching evolutionary paradigm that took shape by the 1940s and scientists generally accept today

Question 26

nonrandom mating

Answer 26

changes in a population’s gene pool due to mate choice or other forces that cause individuals to mate with certain phenotypes more than others

Question 27

population genetics

Answer 27

study of how selective forces change the allele frequencies in a population over time

Question 28

population variation

Answer 28

distribution of phenotypes in a population

Question 29

relative fitness

Answer 29

individual’s ability to survive and reproduce relative to the rest of the population

Question 30

selective pressure

Answer 30

environmental factor that causes one phenotype to be better than another

Question 31

sexual dimorphism

Answer 31

phenotypic difference between a population's males and females

Question 32

stabilizing selection

Answer 32

selection that favors average phenotypes