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Evolution + phylogeny > WOLF > Flashcards

WOLF Flashcards

(109 cards)

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1
Q

what are the 3 requirements for evolution by natural selection?

A

trait variation
fitness differences associated with traits
inheritance of traits

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2
Q

what is selection differential?

A

the difference between the mean trait value of selected individuals and the mean trait value of the overall population

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3
Q

what does a trait distribution curve show?

A

a bell-shaped curve representing the range and frequency of trait values in a population

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4
Q

what is darwinian fitness?

A

an individual’s contribution to the next generation often measure by the number of offspring produced

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5
Q

what is relative fitness?

A

an individual’s fitness compared to the population average (individual fitness/ mean fitness)

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6
Q

why is early reproduction favoured by selection?

A

because it accelerates lineage growth by starting the next gen sooner

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7
Q

what does a large selection differential mean?

A

the greater the change expected in the next generation’s trait value

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8
Q

what is malthusian fitness?

A

the exponential growth rate of a population - influenced by reproductive timing and fecundity

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9
Q

what is an exaptation?

A

a trait that serves a function today but originally evolved for a different purpose

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10
Q

what are vestigial traits?

A

former adaptations that no longer serve a purpose

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11
Q

what are constraints on evolution?

A

limitations that prevent populations from reaching an optimal trait outcome

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12
Q

what are physical constraints?

A

limits imposed by the laws of physics

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13
Q

what is antagonistic pleiotropy?

A

when one gene affects multiple traits in opposing ways (increased longevity reduces early fecundity)

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14
Q

why doesn’t evolution always reach the best outcome?

A

because some optimal traits require passing through low fitness stages which selection tends to avoid

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15
Q

what’s an example of selection without evolution?

A

it a trait affects fitness but is not heritable, selection occurs but there is no evolutionary change

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16
Q

what does the height of an adaptive landscape represent?

A

fitness as a function of traits/ genotypes

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17
Q

what do the axes of an adaptive landscape represent?

A

traits or genetic properties of individuals or populations

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18
Q

how do populations move in an adaptive landscape?

A

by climbing towards peaks - representing higher fitness

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19
Q

what is phenotype space?

A

a multidimensional space where each trait is a dimension and individuals aare points defined by their trait values

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20
Q

what are local fitness peaks?

A

points where fitness is locally maximised but not ecessarily the highest overall - populations can get trapped there

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21
Q

how do mutation size and variation affect adaptive landscapes?

A

small mutations - gradual climbing of local slopes

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22
Q

how do ecological factors shape fitness surfaces?

A

through complex interactions such as predator prey dynamics or environmental pressures

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23
Q

what is the differencccs between individual fitness surface and population fitness surface?

A

Individual fitness surface = relationship between traits and an individual’s fitness.

Population fitness surface = movement of average trait values over time.

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24
Q

what is the relationship between genotype and phenotype in evolution?

A

selection acts on phenotypes but evolution occurs through genetic change

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25
what is rugged landscape?
a landscape with many fitness peaks - reflecting genetic interactions and multiple adaptive solutions
26
how can rugged landscapes explain speciation?
different populations can evolve to different peaks
27
what is a smooth landscape in evolutionary terms?
a landscape with a single peak - where selection leads to an optimal solution
28
what is evolutionary equilibrium?
a state where allele frequencies or phenotypes remain stable in the adaptive landscape
29
what is a stable equilibrium?
a population at a fitnesspeak - if disturbed, selection pushes it back to the peak
30
what is an unstable equilibrium?
a population sits between 2 peaks and any distrubance pushes it to one side
31
what is neutral equilibrium?
multiple trait combinations yield equal fitness and shifting doesn't reduce fitness
32
what is mixed equilibrium?
fitness is maintained along a ridge where traits co-vary
33
how does the adaptive landscape help conceptualise evolution?
it visualises how traits and mutations interact with fitness showing possible evolutionary paths and constraints
34
what are the 2 main processes that contribute to evolution?
deterministic processes (natural selection) and random processes (genetic drift)
35
what is the key chatacteristic of deterministic processes in evolution?
they predict outcomes based on known factors like genotype-phenotype relationships
36
what is the key characteristic of random processes in evolution?
they introduce unpredictability such as genetic drift
37
how is selection considered a deterministic process?
selection is predictable if we understand the fitness of different genotypes and phenotypes
38
what is frequency independent selection?
fitness of a genotype doesn't depend on allele frequencies
39
what are the 3 ttypes of selection under frequency independent selection?
directional selection overdominance - higher fitness of heterozygote underdominance - lower fitness of heterozygote
40
what is directional selection?
it favours individuals with traits at one extreme of a phenotypic range, shifting the populations trait distribution toward that extreme
41
How does directional selection act on alleles and phenotypes?
Selection acts on phenotypes, which leads to changes in allele frequencies based on the genotype-phenotype relationship
42
How do dominant alleles behave under directional selection?
Dominant alleles experience rapid initial frequency changes due to Hardy-Weinberg proportions but slow down as they become more common
43
how does genotype-phenotype relationship influence allele frequency changes?
rare alleles increase faster if dominant or codominant, while recessive alleles increase slowly but go to fixation faster once common
44
what happens to alleles under frequency independent directional selection?
the allele frequency of the favoured allele increases over time
45
how does selection act on rare alleles?
rare alleles increase in frequency more quickly if they are dominant or codominant
46
What happens to an allele once it becomes common in a population under natural selection?
Once common, the allele increases in frequency more quickly if recessive than dominant or codominant
47
What effect does genotype-phenotype relationship have on evolutionary dynamics?
It determines how alleles change in frequency over time, especially in the presence of selection pressures
48
does selection always lead to the fixation of an allele?
no it can result in a polymorphic equilibroum where multiple alleles are retained
49
what is deterministic fixation of alleles?
when an allele is favoured by selection, causing it to go into fixation
50
what is trivial equilibria?
occur when an allele is fixed or absent in the pop, there is no intermediate
51
what is evolutionary equilibria?
where nothing changes and allele and phenotype frequencies remain stable
52
what assumptions must be met for a population to return to a hardy weingberg equilibrium?
the pop must have no selection, random mating and no migration or mutation
53
what kind of equilibrium is the hardy-weingberg equilibrium?
neutral equilibrium where allele and genotype frequencies are constant with no random mating, selection, mutation or migration
54
what does overdominance (heterozygote advantage) cause in terms of equilibrium?
overdominance leads to a stable equilibrium
55
how does overdominance maintain alleles in a population?
it allows rare alleles to persist due to their fitness advantage in heterozygotes
56
what is the adaptive landscape view of overdominance?
leads to a stable polymorphism where populations evolve toward an equilibrium that maximises average fitness
57
what is underdominance and how does it relate to equilibrium?
where the heterozygote has a lower fitness than the homozygote, leading to an unstable equilibrium where small deviations lead to the fixation of 1 allele
58
how does underdominance affect polymorphisms?
results in unstable polymorphisms where small changes in allele frequencies can result in fixations of singular alleles
59
what is positive frequency dependent selection?
where common phenotypes have advantages so they increase in frequency
60
what is negative frequency dependent selection?
favours rare phenotypes, providing a fitness advantage e.g. predator-prey interactions
61
what is the impact of positive frequency dependent selection on genetic variation?
it reduces variation because it favours common traits which leads to one allele being more prevalent
62
what is the impact of negative frequency dependent selection on genetic variation?
it maintains variation by favouring rare traits
63
what role to random processes play in evolution despite deterministic selection?
mutation, drift and finite pop size can contribute to allele frequency changes
64
how does population size affect genetic drift?
smaller populations experience strogner dirft as random fluctuations have a bigger impact
65
does genetic drift lead to adaptation?
no - it is non-adaptive so it fixes alleles regardless of their effect on fitness
66
can drift overpower natural selection?
yes, especially in small populations - this allwos neutral alleles/ deleterious alleles to spread
67
what is a known relationship based upon deterministic processes?
genotype-phenotype relationship - it provides a predictable outcome
68
why is selection considered a deterministic process?
because if we know the fitness of a genotype/phenotype, we can predict how allele frequencies will change
69
what is frequency-independent selection?
a form of selection where the fitness of genotypes doesn't depend on their frequency in the pop
70
name 3 examples of frequency independent selection:
directional selection - one allele is always favoured overdominance - heterozygote advantage underdominance - heterozygote disadvantage
71
what is frequency dependent selection?
where the fitness of a trait/ genotype changes based upon its frequency in a pop
72
how does directional selection affect a favoured allele?
it increases in frequency over time
73
why does a rare dominant allele increase quickly under selection?
because most of its copies are in heterozygotes which can express the advantageous phenotype
74
what does pq represent in evolutionary models?
the allelic variation in the population - product of the frequecies of 2 alleles (p+q)
75
how does pq affect selection?
greater pq means more heterozygotes so selection changes allele frequencies more efficiently
76
are common alleles found in heterozygotes or homozygotes more often?
homozygotes
77
What happens to favored alleles under directional selection in deterministic models?
They typically go to fixation, with the rate depending on dominance and initial frequency
78
what are the 5 key assumptions of the hardy weinberg model?
no selection, random mating, no mutation, no selection and infinite pop size
79
What happens to HW equilibrium after one generation of random mating?
A population returns to Hardy-Weinberg proportions in a single generation of random mating
80
what is non-random mating?
when mating relies on phenotype/ relatedness
81
what is the inbreeding coefficient (F)?
the probability that 2 alleles are identical by descent - measures deviation from HW due to inbreeding
82
what does F>0 indicate?
inbreeding so there is an excess of homozygotes and reduced heterozygosity
83
what does F<0 indicate?
outbreeding - excess of heterozygotes and increased heterozygosity
84
what is identity by descent?
when allels are copied from the same ancestor leading to autozygosity
85
how is inbreeding different from genetic drift?
inbreeding affects genotype combinations whereas genetic drift affects allele frequencies
86
what does inbreeding do to heterozygosity?
loss of heterozygosity
87
what is inbreeding depression?
reduced fitness caused by loss of heterozygosity
88
how do deleterious recessive alleles persist in populations?
they are mosstly found in heterozygotes where their effects are hidden
89
what is outbreeding?
preference for mating with genetically different individuals - increasing heterozygosity
90
what is positive assortative mating?
mating between phenotypically similar individuals; decreases heterozygosity
90
what is disassortative mating?
mating between phenotypically dissimilar individuals
91
how does drift differ from inbreeding in genome wide patterns in terms of loci?
drift affects loci independently whereas inbreeding affects all loci equally by reducing heterozygosity
92
what is a metapopulation?
a population of populations - individuals can move between these subpopulations
93
what is a structured population?
most individuals mate locally leading to genetic differences among subpops
94
what is Fst?
a measure of genetic differentiation - the reduction in heterozygosity across subpopulations compared to a single randomly mating pop
95
what do HT and HS represent?
HT = expected heterozygosity observed across metapopulation HS = average observed heterozygosity within subpops
96
what does a high Fst indicate?
high genetic differentiation between pops (high heterozygosity)
97
what is the wahlund effect?
reduced heterozygosity in a structured pop due to different allele frequencies between subpops
98
how is the wahlund effect different from inbreeding?
Both reduce heterozygosity, but Wahlund is due to population structure; inbreeding is due to mating between relatives
99
what is isolate breaking?
mizing of subpopulations increases heterozygosity which counteracts the wahlund effect
100
what reduces FST?
migration (gene flow)
101
describe the continent island model of migration:
a large source pop sends migratns one-way to a smaller pop at rate m
102
describe the island model of migration:
equal-sized pops exchange migrants at rate m, converging toward global allele freqs
103
what is the stepping stone model?
gene flow only occurs between adjacent populations
104
what is isolation by distance?
genetic similarity declines with distance due to local mating and limited dispersal
105
what is a viscous population?
one where mating is local, causing spatial variation in allele frequencies
106
what is migration-drift balance?
equilibrium were drift increases differentiation and migration reduces it
107
how does drift affect Fst?
drift increases Fst (divergence)
108
how does migration affect Fst?
reduces Fst (homogenisation)

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