Chapter 23-The Evolution of Populations

Question 1

Natural selection acts on individuals but…

Answer 1

only populations evolve

Question 2

Microevolution

Answer 2

Is a change in allele frequencies in a population over generations

Question 3

What three mechanisms cause allele frequency change

Answer 3

1. Natural selection
2. Genetic drift
3. Gene flow

Question 4

Genetic drift

Answer 4

chance events that alter allele frequencies

Question 5

gene flow

Answer 5

transfer of alleles between populations

Question 6

What is a prerequisite for evolution

Answer 6

variation in heritable traits

Question 7

What causes genetic variation among individuals

Answer 7

differences in genes or other DNA segments

Question 8

Phenotype

Answer 8

is the product of inherited genotype and environmental influences

Question 9

_________ can only act on variation with a genetic component

Answer 9

Natural selection

Question 10

Genetic variation can be measured as

Answer 10

gene variability or nucleotide variability

Question 11

GV of gene variability

Answer 11

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

Question 12

GV Nucleotide variability

Answer 12

is measured by comparing the DNA sequences of pairs of individuals

Question 13

Genetic variation at the whole gene level can be quantified as

Answer 13

the average percentage of loci that are heterozygous

Question 14

New genes and alleles can arise by

Answer 14

mutations or gene duplication

Question 15

A mutation

Answer 15

is a change in nucleotide sequence of DNA

Question 16

What type of mutations can be passed off to offspring

Answer 16

mutations in cells that produce gametes

Question 17

Point mutation

Answer 17

is a change in one base in a gene

Question 18

Mutations in noncoding DNA

Answer 18

mostly harmless

Question 19

Mutations in genes

Answer 19

can be neutral because of redundancy in the gentic code

Question 20

Mutations that result in a change in protein production

Answer 20

often harmful, but can sometimes be beneficial

Question 21

Chromosomal mutations that delete, disrupt, or rearrange many loci

Answer 21

are typically harmful

Question 22

Duplication of small pieces of DNA increase genome size

Answer 22

usually less harmful

Question 23

duplicated genes

Answer 23

can take on new functions by further mutation

Question 24

Mutation rates in animals and plants are

Answer 24

low

Question 25

average of a mutation is

Answer 25

one mutation in every 100,000 genes per generation

Question 26

Mutation rates are often lower in prokaryotes

Answer 26

and often higher in viruses

Question 27

Mutation rates are often higher in viruses

Answer 27

and often lower in prokaryotes

Question 28

Sexual reproduction has the possibility to

Answer 28

shuffle existing alleles into new combinations

Question 29

A Population

Answer 29

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

Question 30

A gene pool

Answer 30

consists of all the alleles for all loci in a population

Question 31

If all individuals in a population are homozygous for the same allele

Answer 31

A locus is fixed

Question 32

Hardy-Weinberg principle describes

Answer 32

a population that is not evolving

Question 33

Five conditions for Hardy-Weinberg Equilibrium

Answer 33

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

Question 34

Three major factors alter allele frequencies and bring about most evolutionary change

Answer 34

1. Natural selection 2. Genetic drift 3. Gene flow

Question 35

Natural selection

Answer 35

differential success in reproduction results in certain alleles being passed to the next generation in greater proportions

Question 36

Genetic drift

Answer 36

The smaller a sample, the greater the chance of deviation from a predict result

Question 37

Genetic drift describes

Answer 37

how allele frequencies fluctuate unpredictably from one generation to the next

Question 38

Genetic drift tends to

Answer 38

reduce genetic variation through losses of alleles

Question 39

The founder effect

Answer 39

occurs when a few individuals become isolated from a large population

Question 40

The bottleneck effect

Answer 40

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

Question 41

Genetic drift is significant in

Answer 41

small populations

Question 42

genetic drift causes allele frequencies to

Answer 42

change at random

Question 43

Genetic drift can lead to a loss of

Answer 43

genetic variation within populations

Question 44

Genetic drift can cause

Answer 44

harmful alleles to become fixed

Question 45

Gene flow

Answer 45

consists of the movement of alleles among populations

Question 46

Gene flow tend to

Answer 46

reduce variation among populations over time

Question 47

Gene flow can

Answer 47

decrease the fitness of a population or increase the fitness of the population

Question 48

Natural selection it the only mechanism that

Answer 48

consistently causes adaptive evolution

Question 49

How does natural selection bring about adaptive evolution

Answer 49

by acting on an organism's phenotype

Question 50

Relative fitness

Answer 50

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

Question 51

Three modes of selection

Answer 51

1. Directional selection 2. Disruptive selection 3. Stabilizing selection

Question 52

Directional selection

Answer 52

favors individuals at one end of the phenotypic range

Question 53

Disruptive selection

Answer 53

favors individuals at both extremes of the phenotypic range

Question 54

Stabilizing selection

Answer 54

favors intermediate variants and acts against extreme phenotypes

Question 55

Sexual selection

Answer 55

is natural selection for mating success

Question 56

Sexual dimorphism

Answer 56

marked differences between the sexes in secondary sexual characteristics

Question 57

Intrasexual selection

Answer 57

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

Question 58

Intersexual selection-mate choice

Answer 58

occurs when individuals of one sex are choosy in selection their mates

Question 59

Neutral variation

Answer 59

genetic variation that does not confer a selective advantage or disadvantage

Question 60

Diploidy maintains genetic variation in the form of

Answer 60

hidden recessive alleles

Question 61

Heterozygotes

Answer 61

can carry recessive alleles that are hidden from the effects of selection

Question 62

Balancing selection

Answer 62

occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population

Question 63

Balancing selection includes

Answer 63

1. Heterozygote advantage | 2. Frequency-dependent selection

Question 64

Heterozygote advantage

Answer 64

when heterozygotes have a higher fitness than do both homozygotes

Question 65

Frequency-dependent selection

Answer 65

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

Question 66

Natural Selection cannot

Answer 66

fashion perfect organisms

Question 67

Natural selection cannot fashion perfect organisms

Answer 67

1. selection can act only on existing variations 2. Evolution is limited by historical constraints 3. Adaptations are often compromises 4. Chance, natural selection, and the environment interact