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Biology Ch20-24 > Chapter 23-The Evolution of Populations > Flashcards

Chapter 23-The Evolution of Populations Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Natural selection acts on individuals but…

A

only populations evolve

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2
Q

Microevolution

A

Is a change in allele frequencies in a population over generations

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3
Q

What three mechanisms cause allele frequency change

A
  1. Natural selection
  2. Genetic drift
  3. Gene flow
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4
Q

Genetic drift

A

chance events that alter allele frequencies

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5
Q

gene flow

A

transfer of alleles between populations

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6
Q

What is a prerequisite for evolution

A

variation in heritable traits

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7
Q

What causes genetic variation among individuals

A

differences in genes or other DNA segments

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8
Q

Phenotype

A

is the product of inherited genotype and environmental influences

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9
Q

_________ can only act on variation with a genetic component

A

Natural selection

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10
Q

Genetic variation can be measured as

A

gene variability or nucleotide variability

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11
Q

GV of gene variability

A

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

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12
Q

GV Nucleotide variability

A

is measured by comparing the DNA sequences of pairs of individuals

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13
Q

Genetic variation at the whole gene level can be quantified as

A

the average percentage of loci that are heterozygous

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14
Q

New genes and alleles can arise by

A

mutations or gene duplication

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15
Q

A mutation

A

is a change in nucleotide sequence of DNA

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16
Q

What type of mutations can be passed off to offspring

A

mutations in cells that produce gametes

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17
Q

Point mutation

A

is a change in one base in a gene

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18
Q

Mutations in noncoding DNA

A

mostly harmless

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19
Q

Mutations in genes

A

can be neutral because of redundancy in the gentic code

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20
Q

Mutations that result in a change in protein production

A

often harmful, but can sometimes be beneficial

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21
Q

Chromosomal mutations that delete, disrupt, or rearrange many loci

A

are typically harmful

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22
Q

Duplication of small pieces of DNA increase genome size

A

usually less harmful

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23
Q

duplicated genes

A

can take on new functions by further mutation

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24
Q

Mutation rates in animals and plants are

A

low

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25
Q

average of a mutation is

A

one mutation in every 100,000 genes per generation

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26
Q

Mutation rates are often lower in prokaryotes

A

and often higher in viruses

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27
Q

Mutation rates are often higher in viruses

A

and often lower in prokaryotes

28
Q

Sexual reproduction has the possibility to

A

shuffle existing alleles into new combinations

29
Q

A Population

A

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

30
Q

A gene pool

A

consists of all the alleles for all loci in a population

31
Q

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

A

A locus is fixed

32
Q

Hardy-Weinberg principle describes

A

a population that is not evolving

33
Q

Five conditions for Hardy-Weinberg Equilibrium

A
  1. No mutations
  2. Random mating
  3. No natural selection
  4. no gene flow
  5. Extremely large population size
34
Q

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

A
  1. Natural selection
  2. Genetic drift
  3. Gene flow
35
Q

Natural selection

A

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

36
Q

Genetic drift

A

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

37
Q

Genetic drift describes

A

how allele frequencies fluctuate unpredictably from one generation to the next

38
Q

Genetic drift tends to

A

reduce genetic variation through losses of alleles

39
Q

The founder effect

A

occurs when a few individuals become isolated from a large population

40
Q

The bottleneck effect

A

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

41
Q

Genetic drift is significant in

A

small populations

42
Q

genetic drift causes allele frequencies to

A

change at random

43
Q

Genetic drift can lead to a loss of

A

genetic variation within populations

44
Q

Genetic drift can cause

A

harmful alleles to become fixed

45
Q

Gene flow

A

consists of the movement of alleles among populations

46
Q

Gene flow tend to

A

reduce variation among populations over time

47
Q

Gene flow can

A

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

48
Q

Natural selection it the only mechanism that

A

consistently causes adaptive evolution

49
Q

How does natural selection bring about adaptive evolution

A

by acting on an organism’s phenotype

50
Q

Relative fitness

A

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

51
Q

Three modes of selection

A
  1. Directional selection
  2. Disruptive selection
  3. Stabilizing selection
52
Q

Directional selection

A

favors individuals at one end of the phenotypic range

53
Q

Disruptive selection

A

favors individuals at both extremes of the phenotypic range

54
Q

Stabilizing selection

A

favors intermediate variants and acts against extreme phenotypes

55
Q

Sexual selection

A

is natural selection for mating success

56
Q

Sexual dimorphism

A

marked differences between the sexes in secondary sexual characteristics

57
Q

Intrasexual selection

A

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

58
Q

Intersexual selection-mate choice

A

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

59
Q

Neutral variation

A

genetic variation that does not confer a selective advantage or disadvantage

60
Q

Diploidy maintains genetic variation in the form of

A

hidden recessive alleles

61
Q

Heterozygotes

A

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

62
Q

Balancing selection

A

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

63
Q

Balancing selection includes

A
  1. Heterozygote advantage

2. Frequency-dependent selection

64
Q

Heterozygote advantage

A

when heterozygotes have a higher fitness than do both homozygotes

65
Q

Frequency-dependent selection

A

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

66
Q

Natural Selection cannot

A

fashion perfect organisms

67
Q

Natural selection cannot fashion perfect organisms

A
  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

Biology Ch20-24 (3 decks)

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