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foundations of biology > ch 23: evolutionary processes > Flashcards

ch 23: evolutionary processes Flashcards

(75 cards)

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1
Q

what did hardy and weinburg want to discover?

A

what happened in an entire population when all individuals, including all genotypes, bred with each other

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2
Q

gene pool

A

all the alleles of all the genes in a certain population

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3
Q

what does a gene pool represent?

A

random mating

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4
Q

what does hardy-weinberg calculate?

A

predictions of genotypes of offspring that population would produce, as well as frequency of each genotype

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5
Q

what does the hardy-weinberg principle serve as?

A

a null hypothesis for studies of evolutionary processes

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6
Q

hardy-weinberg equilibrium

A

state of agreement between observed allele frequencies in a population and allele frequencies predicted assuming that evolution is not occurring and mating is random

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7
Q

what is the hardy-weinberg principle stating?

A

allele frequencies do not change over time, meaning the population is not evolving

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8
Q

equation for frequencies of alleles under HW

A

p + q = 1

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9
Q

equation for frequencies of genotypes under HW

A

p^2 + 2pq + q^2

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10
Q

what are the assumptions of hardy-weinberg?

A
  1. random mating
  2. no natural selection
  3. no genetic drift
  4. no gene flow
  5. no mutation
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11
Q

what are the four processes that drive evolution?

A
  1. natural selection
  2. genetic drift
  3. gene flow
  4. mutation
    - all violate hardy-weinberg
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12
Q

what do the four processes cause?

A

allele frequencies in a population to change over time

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13
Q

what does nonrandom mating cause?

A

change in genotype frequencies but not allele frequencies

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14
Q

when is hardy-weinberg equilibrium used as a null hypothesis?

A

when biologists want to test a hypothesis that nonrandom mating is occurring or that one of then evolutionary processes is affecting a particular trait in a population

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15
Q

assortative mating

A

individuals with similar phenotypes or genotypes are more likely or less likely to mate with each other

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16
Q

inbreeding

A

nonrandom mating between relatives

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17
Q

what does inbreeding increase and decrease?

A
  • increases frequency of homozygotes
  • decreases frequency of heterozygotes
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18
Q

does inbreeding change allele or genotype frequencies?

A

genotype
- therefore it does not cause evolution

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19
Q

self-fertilization

A

most extreme form of inbreeding

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20
Q

what offspring will homozygous parents that self-fertilize produce?

A

all homozygous offspring

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21
Q

what offspring will heterozygous parents that self-fertilize produce?

A

homozygous and heterozygous offspring
1:2:1 ration

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22
Q

is nonrandom mating an evolutionary process?

A

no because it changes genotype frequency not allele frequency

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23
Q

how does inbreeding speed the rate of evolutionary change?

A

by increasing the rate at which natural selection eliminates recessive deleterious alleles (that lower fitness) from a population

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24
Q

inbreeding depression

A

a decline in average fitness takes place when homozygosity increases and heterozygosity decreases in population

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25
what population is inbreeding depression common in?
small population
26
sexual selection
nonrandom mating where an organism actively choses a certain mate based on physical and behavioral traits
27
does sexual selection drive evolution?
yes because it changes allele frequencies and increases fitness - form of natural selection
28
what does sexual selection favor?
traits that enhance an individual's chances of reproduction but reduce its chances of survival
29
when does natural selection occur?
individuals with certain phenotypes produce more surviving offspring than do individuals with other phenotypes - alleles associated with favored phenotypes increase in frequency while other alleles decrease
30
genetic variation
number and relative frequency of alleles present in particular population
31
why is lack of genetic variation a bad thing?
selection can only occur if heritable variation exists in a population
32
what could happen if the genetic variation is low and environment changes?
the available alleles may not be able to survive and reproduce causing average fitness to decline - could lead to extinction
33
modes of natural selection
1. directional selection 2. stabilizing selection 3. disruptive selection 4. balancing selection
34
directional selection
mode of natural selection that favors one extreme phenotype with the result that the average phenotype of a population changes in one direction
35
does directional selection increase or decrease genetic variation?
decrease - can lead to fixed and lost alleles
36
purifying selection
selection that lowers frequency or eliminates deleterious alleles
37
stabilizing selection
a mode of natural selection that favors phenotype near the middle of the range of phenotypic variation
38
does stabilizing selection increase or decrease genetic variation?
decrease
39
does the average value of a trait change over time with stabilizing selection?
no
40
disruptive selection/
mode of natural selection that favors extreme phenotypes at both ends of the range of phenotypic variation
41
does disruptive selection increase or decrease genetic variation?
increase
42
what phenotypes are eliminated and which are favored in disruptive selection?
eliminated: phenotypes near average value favored: extreme phenotypes
43
does disruptive selection favor new alleles?
yes, it can favor new alleles that contribute to extreme values of a trait
44
what can disruptive selection play a role in?
speciation: the formation of new species
45
balancing selection
mode of natural selection in which no single allele is favored over time and across locations
46
does any phenotype have an advantage with balancing selection?
no
47
what are the 2 types of balancing selection?
1. heterozygous advantage 2. frequency-dependent selection
48
heterozygous advantage
occurs when heterozygous individuals have higher fitness than homozygous individuals do
49
what does balancing selection maintain?
genetic variation
50
frequency-dependent selection
occurs when certain alleles are favored when they are rare but not when they are common
51
genetic drift
change in allele frequencies in population due to chance
52
what is genetic drift known as in statisitics?
sampling error
53
what does genetic drift cause?
allele frequencies drift up and down randomly over time
54
what populations are genetic drifts common in?
small populations - allele frequencies change much less in large populations
55
what can genetic drifts lead to over time?
random loss or fixation of alleles - results in a decrease in genetic variation
56
is genetic drift random with respect to fitness?
yes
57
population bottleneck
sudden decreases in population size in large population - caused by natural catastrophes or disease outbreaks - lead to genetic bottleneck
58
genetic bottleneck
sudden reduction in the number of alleles in a population - genetic drift occurs during this time and causes change in allele frequencies
59
founder effect
allele frequencies likely differ from source population if new population is small enough - causes a resulting change in allele frequencies
60
founder event
occurs when group of individuals establish new population in new area
61
gene flow
movement of alleles between populations
62
when does gene flow occur?
when individuals leave one population, join another, and breed
63
what does gene flow equalize?
allele frequencies between source and recipient populations
64
does gene flow reduce fitness?
not always, because it can replenish alleles in populations that has lost alleles due to genetic drift which INCREASES genetic diversity
65
mutation
permanent change in the hereditary material of an organism
66
what do mutations create?
new alleles which generate genetic diversity
67
point mutations
change in one single base pair in DNA
68
what can point mutations result in?
same, similar, or different amino acid
69
what can point mutations change?
the regulation of the expression of other genes
70
chromosome-level mutations
change in the number or composition of chromosomes, such as gene and genome duplication
71
lateral gene transfer
movement of genes between different "species"
71
beneficial allele mutations
an allele that allows individuals to produce more surviving offspring, increasing fitness - increase in frequency due to natural selection
72
neutral allele mutations
an allele with no effect on fitness, as occurs when a point mutation is silent
73
deleterious allele mutations
alleles that lower fitness and are eliminated by purifying selection
74
when do mutations have a large effect?
when combined with natural selection, genetic drift, or gene flow

foundations of biology (33 decks)

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