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Biology 1020 > Evolution of Population > Flashcards

Evolution of Population Flashcards

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1
Q

What are the main mechanisms of evolutionary change?

A

Natural selection
Genetic drift
Gene flow

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2
Q

what is the modern synthesis

A

theory that reconciled Darwinian selection theory with Mendelian genetics to explain the origin of biological diversity

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3
Q

why doesn’t natural selection produce “perfect” organisms

A
  1. Selection can act ONLY on existing variations
  2. evolution is limited by historical constraints
  3. Adaptations often comprise
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4
Q

what is blended inheritance

A
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5
Q

what is the inheritance of acquired characters

A
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6
Q

why have notions of inheritance of acquired characters AND blended inheritance fallen into disfavor

A
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7
Q

what is Mendel’s contribution to genetics?

A

discovered the fundamental laws of inheritance
set the stage for understanding the genetic differences base of evolution

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8
Q

where does genetic variation come from

A

Mutations, Gene duplication and sexual reproduction

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9
Q

explain how heterozygote advantage maintains detrimental alleles (sickle cell anemia)

A

dominant allele protects them from a genetic disease, while their recessive allele protects them from an infectious disease

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10
Q

three ways sexual reproduction contributes to genetic variation

A
  1. crossing over
  2. an independent assortment of chromosomes
  3. fertilization
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11
Q

how would a point mutation FAIL to change the effect of a natural selection on an organism

A

Point mutations in noncoding regions commonly result in neutral variation (no advantage or disadvantage to organism)

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12
Q

how is the Hardy-Weinberg equation used to determine if a population is evolving

A

determines what the genetic makeup of a population would be if it’s NOT evolving at that locus and then compares it to the current population

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13
Q

what are the parts of the HW equation

A

P, PQ and Q

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14
Q

explain this statement :
“Mendelian processes alone DO NOT alter allele frequencies”

A

if these were the only processes at work then there would be no change to the allele frequency.

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15
Q

a common misconception about evolution

A

individual organisms evolve

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16
Q

even though natural selection acts on individuals the impact is ONLY seen

A

at the population level

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17
Q

what reduces genetic variation

A

population bottleneck

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18
Q

less genetic variation means there is

A

less opportunity for natural selection to adapt to environmental pressures

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19
Q

what is evolution on its smallest scale

A

microevolution

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20
Q

microevolution

A

changes in allele frequencies in a population over generations

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21
Q

TRue or false
natural selection is the ONLY cause of microevolution

A

FALSE

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22
Q

what is the mechanism to CONSISTENTLY improve the match of organisms and environment

A

natural selection

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23
Q

genetic drift

A

chance events that alter allele frequencies

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24
Q

gene flow

A

the transfer of alleles between populations

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25
Q

what is a prerequisite for mechanisms that cause allele frequency changes/evolution

A

genetic variation

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26
Q

what makes evolution possible

A

genetic variation

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27
Q

what didn’t Darwin know about organisms

A

HOW they pass heritable traits to their offspring

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28
Q

who set the stage for understanding the genetic differences of evolution

A

Mendel

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29
Q

True or False
Individuals in the same species will vary in phenotypic traits

A

TRUE

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30
Q

True or False
phenotypic variations DON’T reflect genetic variation

A

FALSE

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31
Q

how does phenotypic variation reflect genetic variation

A

differences among individuals in the composition of their genes or DNA sequences

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32
Q

what is suggested by heritable phenotypic differences occurring on an “either-or” basis

A

typically determined by a SINGLE gene locus with different alleles producing different phenotypes

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33
Q

what is suggested by phenotypic differences that vary along a continuum

A

result from influence of two or more gees on a single phenotypic character

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34
Q

Genetic variation at the whole-gene level can be quantified as the

A

the average percentage of loci that are heterozygous

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35
Q

Genetic variation at the molecular level of DNA has

A

very little variation resulting in phenotypic variation

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36
Q

why does genetic variation at the molecular level NOT result in phenotypic variation

A

Most of the variations occur in introns

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37
Q

what is phenotype a product of

A

inherited genotype and many environmental influences

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38
Q

what part of phenotypic variation can have evolutionary consequences

A

only genetically determined part

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39
Q

true or false
evolution can occur without genetic variation

A

FALSE

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40
Q

genetic variation evolution depends on

A

processes that produce new alleles and genes

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41
Q

true or false
sexual reproduction can also result in genetic variation

A

true

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42
Q

why can sexual reproduction result in genetic variation

A

genes are arranged in new ways

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43
Q

new alleles can arise from

A

mutations

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44
Q

mutations

A

change in the nucleotide sequence of an organism’s DNA

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45
Q

most NEW mutations that alter a phenotype are

A

at least slightly harmful

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46
Q

how can diploid organisms can hide harmful alleles

A

harmful alleles that are recessive can be hidden from selection by heterozygote protection

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47
Q

heterozygote protection

A

more favourable dominant allele can mask the recessive harmful one

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48
Q

True or false
a mutation can, on occasion, make its bearer better suited to the environment

A

TRUE

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49
Q

what is the ONLY way mutations can be passed to offspring in multicellular organisms

A

mutations in cell lines that produce gametes

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50
Q

what chromosomal changes are usually harmful

A

changes that delete, disrupt or rearrange

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51
Q

how can changes not affect phenotype

A

large scale changes that leave genes intact

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52
Q

key source of varaition

A

duplication of genes due to error in meiosis

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53
Q

example of how an error in meiosis cause variation

A

unequal crossing over

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54
Q

duplication of large chromosomal segments would be

A

harmful

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55
Q

duplications of smaller pieces of DNA may

A

not be harmful

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56
Q

what happens when mutations accumulate with gene duplications over generations with NO effects

A

expanded genome with new genes

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57
Q

mutations tend to be _____ in plants and animals

A

low

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58
Q

prokaryotes often have _____ number of mutations than plants and animals

A

lower

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59
Q

what is the link between more generations of time and mutations (prokaryotes)

A

mutations quickly generate genetic variation in populations

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60
Q

what type of genome has a higher mutation rate

A

RNA genome compared to the DNA genome

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61
Q

Most of the genetic variation in the population comes from

A

the unique combination of alleles each individual receives from parents

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62
Q

sexual reproduction shuffles ______ and deals them _______ to produce individual genotypes

A

existing alleles AND randomly

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63
Q

what is used to test whether a population is evolving

A

HW equation

64
Q

does genetic variation guarantee that a population will evolve

A

NO

65
Q

population

A

group of individuals of the same species living in the same area and interbreed

66
Q

what does interbreeding cause

A

makes individuals more closely related to each other than those of another population

67
Q

true of false
all populations are isolated/have sharp boundaries

A

FALSE

68
Q

what can characterize a population’s genetic makeup

A

gene pool

69
Q

the gene pool consists of

A

all copies of every type of allele at every locus in all members of the population

70
Q

what does it mean if an allele is fixed in the gene pool

A

only one allele exists for a particular locus in a population

71
Q

if an allele is fixed, than it must be

A

homozygous

72
Q

what will a population look like if it’s NOT evolving

A

allele and genotype frequencies will remain constant from generation to generation

73
Q

when is a population said to be in HW equilibrium

A

population is NOT evolving

74
Q

HW principle considers

A

the combination of alleles in ALL of the crosses in a population

75
Q

P2 in HW equilibrium

A

frequency of HOMOZYGOUS DOMINANT genotype

76
Q

2pq

A

frequency of HETEROZYGOUS genotype

77
Q

q2

A

frequency of HOMOZYGOUS RECESSIVE genotype

78
Q

True or false
the population’s gene pool over the generations can change the frequency of one allele relative to another ALONE

A

FALSE

79
Q

departure from the conditions for HW equilibrium can result in

A

evolutionary change

80
Q

5 conditions for HW equilibrium

A
  1. no mutations
  2. random mating
  3. no gene flow
  4. no natural selection
  5. extreme large population sizes
81
Q

what happens if there are mutations in HW equilibrium

A

gene pool is modified

82
Q

what happens if there are no random matings in HW equilibrium

A

interbreeding/ choice breeding = random mixing of gametes DOESN’T occur and genotype frequencies change

83
Q

what happens if there is natural selection in HW equilibrium

A

allele frequencies change when individuals with different genotypes show consistent differences in their survival/reproductive success

84
Q

what happens if there are small population sizes in HW equilibrium

A

allele frequencies fluctuate by chance over time (genetic drift)

85
Q

what happens if there is gene flow in HW equilibrium

A

gene flow can alter allele frequencies

86
Q

natural selection is based on

A

differential success in survival and reproduction

87
Q

adaptive evolution

A

traits that enhance survival or reproduction tend to increase in frequency over time

88
Q

how can natural selection cause adaptive evolution

A

by consistently favouring some alleles over others

89
Q

genetic drift is a major issue for _____ populations

A

small

90
Q

two circumstances that can result in genetic drift having an impact on the population

A
  1. founder effect
  2. bottleneck effect
91
Q

founder effect

A

When a few individuals become isolated from the larger population the smaller group may establish a new population with a gene pool that differs from the source population

92
Q

what accounts for the high frequency of inherited disorders among isolated human populations

A

founder effect

93
Q

bottleneck effect

A

sudden change in the environment can drastically reduce the size of a population

94
Q

what happens to alleles when undergoing a bottleneck

A

they can be overrepresented, underrepresented or absent in the population

95
Q

Genetic drift can cause allele frequencies to

A

change at random

96
Q

how is genetic drift different from natural selection

A

Unlike natural selection which consistently favours some alleles over others, genetic drift causes allele frequencies to change at random over time

97
Q

Genetic drift can lead to loss of

A

genetic variation in populations

98
Q

Genetic drift can cause harmful alleles to

A

become fixed

99
Q

Gene flow

A

transfer of alleles into or out of a population because of the movement of fertile individuals or their gametes

100
Q

true of false
gene flow can reduce genetic differences between populations

A

TRUE

101
Q

only mechanism that consistently causes adaptive evolution

A

natural selection

102
Q

is the outcome of natural selection random

A

NO

103
Q

what are ideas about relative fitness that are MISLEADING

A

Suggestions to mean a direct competitive contests among individuals

104
Q

Relative fitness

A

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

105
Q

selections in relative fitness are more directly on the ______ than the ____

A

phenotype AND genotype

106
Q

Three ways natural selection can alter the frequency of distribution of heritable traits based on what phenotypes favoured

A
  1. directional selection
  2. disruptive selection
  3. stabilizing selection
107
Q

Directional selection

A

When conditions favour individuals exhibiting one extreme of a phenotypic range

108
Q

how does directional selection shift a population’s frequency curve for the phenotypic character

A

in one direction or the other

109
Q

when is directional selection common

A

when population’s environment changes or when members migrate to new habitat

110
Q

what type of selection is this

A

directional selection

111
Q

what type of selection is this

A

disruptive selection

112
Q

what type of selection is this

A

stabilizing selection

113
Q

disruptive selection

A

When conditions favour individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes

114
Q

stabilizing selection

A

Acts against BOTH extreme phenotypes and favours intermediate variants

115
Q

what is the outcome of a stabilizing selection

A

Reduces variation and tends to maintain the status quo for a phenotypic character

116
Q

what happens when there is an increase of favourable traits

A

match between species and environment improves = adaptive evolution occurs

117
Q

adaptive evolution is an _______ process

A

continuous, dynamic

118
Q

true or false
genetic drift and gene flow can consistently increase allele frequency for better survival

A

FALSE

119
Q

ONLY evolutionary mechanism that consistently leads to adaptive evolution

A

natural selection

120
Q

sexual selection

A

Form of selection where individuals with certain inherited traits are more likely than others to obtain mates

121
Q

sexual selection can result in

A

sexual dimorphism

122
Q

two types of sexual selection operations

A

intrasexual selection
intersexual selection

123
Q

intrasexual selection

A

selection within the same sex = individuals of the same sex compete directly for mates of the opposite sex

124
Q

intersexual selection is also called

A

mate choice

125
Q

intersexual selection

A

Individuals of one sex (females usually) are choosy in selecting their mates from the other sex

126
Q

How do female preferences for certain male traits evolve in the first place

A

Females prefer male traits that are correlated with “good genes”

127
Q

Frequency-dependent selection

A

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

128
Q

the frequency-dependent selection would favour the phenotype that is

A

least common

129
Q

how is evolution limited by historical constraints

A

Evolution doesn’t scrap the ancestral form and build a new structure from scratch - co ops existing structures and adapts them to new situations

130
Q

heterozygous advantage is a form of _____ selection

A

stabilizing

131
Q

what was the next great advance in evolutionary biology

A

genetics

132
Q

particulate inheritance

A

trait inherited in chunks called genes

133
Q

phenotype is made up of BOTH

A

genetics and environment

134
Q

if there is zero heterozygosity there then

A

is no genetic variation

135
Q

plasticity

A

a phenotype that changes because of environmental pressures (like predation)

136
Q

is plasticity heritable

A

NO

137
Q

what is more important in genetic variation mutations or sexual reproduction

A

sexual reproduction

138
Q

HW is the _____ hypothesis

A

null

139
Q

if a population is AT HW then it’s

A

NOT evolving

140
Q

if a population that’s evolving at HW equilibrium

A

NO

141
Q

genetic variation AMONG a population is _____ based on drift

A

increasing

142
Q

genetic variation WITHIN a population is _____ based on drift

A

decreasing

143
Q

when does heterozygote advantage reflect directional selection

A

when it shows the extreme phenotype (biggest of anything)

144
Q

when does heterozygote advantage reflect stabilizing selection

A

when it shows the intermediate phenotype

145
Q

what specifies advantageous and disadvantageous traits

A

the environment

146
Q

how does natural selection show chance

A

the environment individuals are found in/the variation that exists in a pop

147
Q

how does natural selection show sorting

A

sorting which phenotype/genotype is selected

148
Q

what level is evolution measured at

A

population

149
Q

what level does NS act on

A

individuals NOT on genotype

150
Q

does the mean phenotype change in directional selection

A

YEs

151
Q

does the mean phenotype change in disruptive selection

A

NO

152
Q

genetic drift ________ genetic variation WITHIN a population

A

decreases

153
Q

genetic drift ________ genetic variation AMONG a population

A

increases

154
Q

gene flow ________ genetic variation WITHIN a population

A

increases

155
Q

gene flow ________ genetic variation AMONG a population

A

decreases

156
Q

does natural selection decrease fitness

A

NO

Biology 1020 (29 decks)

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