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Evolution > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Darwin’s postulates

A

Individuals vary in phenotypes, variation can be passed down (heritable), each generation more offspring produced than can survive, the variants that result in better survival and reproduction will be better represented in next generation (differential survival and reproductive success)

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2
Q

Modern Synthesis

A

Fusion of Darwinian evolution and Mendelian genetics, lead to population and quantitative genetics. Unified macro- and micro-evolution. Highlighted other mechanisms of evolution beside natural selection.

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3
Q

Evolutionary genomics

A

sequencing entire genomes

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4
Q

Group selection

A

for the good of the group

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5
Q

Holes in modern synthesis?

A

Epigenetics, evolutionary developmental biology, meta organisms, prokaryotes

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6
Q

Epigenetics

A

stable phenotypic changes that do not involve alterations in the DNA sequence

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7
Q

evo-devo biology

A

compares the developmental processes of different organisms to infer how developmental processes evolved

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8
Q

How does evo-devo clash with modern synthesis?

A

Highlights an important role for non-coding and regulatory
variation in the evolution of organism body plans. Mutations in
“master” regulatory genes may affect large changes in morphology.

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9
Q

meta-organisms

A

metazoans as “metaorganisms”. These
include the larger organism plus all its endosymbionts (mostly
bacteria). Coevolution between the genomes of endosymbiotic microorganisms and the genome of the host is viewed as a central
consideration in evolutionary change (you can’t understand one without the other).

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10
Q

natural selection

A

variation in relative fitness within a population

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11
Q

absolute fitness (individual)

A

the number of offspring produced by that individual in its lifetime

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12
Q

absolute fitness (population)

A

the population growth rate (absolute fitness of individuals added across all individuals per generation)—this determines the fit of the population to its current environment

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13
Q

relative fitness (individual)

A

number of offspring produced in that individual’s lifetime relative to other individuals in the population - what matters when in comes to adaptive evolution, because it causes changes in gene frequencies and phenotype distributions

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14
Q

Selection differential (S)

A

Strength of selection. S=μ selected - μ1. The phenotype selected for minus the mean phenotype

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15
Q

univariate breeder’s equation

A

R = h^2S. R=response to selection, h^2=narrow sense heritability, S=selection differential/strength of selection

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16
Q

fitness landscape

A

relationship/covariance between trait value and relative fitness

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17
Q

multivariate breeder’s equation

A

ΔZ = Gβ. Z= response (change in the trait in the next generation), G= Matrix (correlation between traits), B=selection gradient (coefficient of selection on multiple traits with itself)

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18
Q

Selection model terms

A

linear, non-linear (univariate), non-linear (bivariate)

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19
Q

linear terms

A

test for positive and negative directional selection on trait means

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20
Q

non-linear - univariate

A

test for selection on trait variance (disruptive or stabilizing selection)

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21
Q

non-linear - bivariate

A

test for correlational selection on pairs of traits

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22
Q

what does positive correlational selection mean for the trait values?

A

favors similar values of traits (low and low, high and high, etc.). negative favor different values (high and low, etc.)

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23
Q

neutral theory

A

most SNP variation occurs because of neutral processes does not negate phenotypic plasticity

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24
Q

narrow sense heritability (h^2)

A

the proportion of phenotypic variance that is due to additive genetic variance (additive genetic variance divided by total phenotypic variance)

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25
Q

h^2=

A

Va/Vp. Va = additive genetic variance. Vp = total phenotypic variation

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26
Q

epistasis

A

the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is dependent on the genetic background in which it appears.

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27
Q

non-additive genetic variance

A

dominance, epistasis

28
Q

Ve=

A

environment, genotype (plasticity)

29
Q

Vp=

A

Va+Vna+Ve

30
Q

Why do we only care about additive genetic effects?

A

includes intermediate values for heterozygotes, selection can actually act on it, while non-additive genetic variance masks the underlying genotype

31
Q

What are the proximate causes of genetic correlations?

A

linkage disequilibrium, pleiotropy

32
Q

linkage disequilibrium

A

non-random association of alleles at different loci in a given population

33
Q

pleiotropy

A

one gene influences two or more seemingly unrelated phenotypic traits

34
Q

what is the ultimate cause of genetic correlations?

A

correlational selection

35
Q

Gmax

A

dimension in trait space for which there is the maximum amount of genetic variance, axis of Matrix over which G is maximal, eigenvalue, path of least resistance

36
Q

genetic drift

A

change in allele frequency in a population due to random sampling of that population (such as random mortality)

37
Q

gene flow

A

movement of genes across space from one population to another

38
Q

chances of a brand new mutation coming to fixation in a population

A

1/2N (N=population). Two alleles per individual

39
Q

mutation-selection balance

A

equilibrium in the number of deleterious alleles in a population that occurs when the rate at which deleterious alleles are created by mutation equals the rate at which deleterious alleles are eliminated by selection. Can be overwhelmed by drift in small populations

40
Q

population bottleneck

A

sudden drop in population size that noticeably alters allele frequency

41
Q

inbreeding depression

A

deleterious alleles increasingly combined into homozygous genotypes

42
Q

background selection

A

losing beneficial alleles because selection acts against the deleterious alleles in the same individual

43
Q

founder effect

A

small subgroup breaks off from larger ancestral population and colonizes a new environment (often invasive species)

44
Q

positives of founder effect

A

novel genetic recombinations that may not have happened in a larger population, possibly allowing for a new phenotype that increases fitness in new environment

45
Q

shifting balance model

A

genetic drift is required to cross fitness valleys and occupy new adaptive peaks

46
Q

positives of gene flow

A

possible transfer of beneficial genes, good for small populations to introduce more genetic variation and novel genes

47
Q

cons of gene flow

A

bad if maladapted for environment and gene swamping occurs, also bad if hitchhiking genes, mess with existing linked genes

48
Q

gene swamping

A

high levels of gene flow can knock population off its local adaptive peak

49
Q

migration selection balance

A

equilibrium, natural selection balances maladapted genetic material received from gene flow

50
Q

genetic rescue

A

gene flow can provide small populations with fresh genetic variation

51
Q

evolutionary rescue

A

new mutation rescues a small, deleterious allele-filled population

52
Q

forces of evolution

A

mutation, natural selection, gene flow, genetic drift

53
Q

There are small populations of grasshoppers living on two islands separated by 1 km of ocean. The environments of these islands differ to the extent that both populations are under equal magnitudes of selection, but in opposite directions. These populations exchange small numbers of migrants each year as individuals will sometimes get caught in storms and blown to the other island. Is it likely that these populations will speciate? How do drift, gene flow, and selection, respectively, influence the probability of speciation?

A

Though it depends on how small these populations are, how many migrants are exchanged, and whether the migration even leads to gene flow, these two populations of grasshoppers will likely not speciate. Genetic drift would decrease genetic variation in each population, likely leading to the accumulation of deleterious alleles because these populations are small. Though the number of migrants is small, gene flow from the migrants would likely provide a much needed source of genetic variation to counteract the deleterious effects of genetic drift. Gene flow is the largest reason speciation would be unlikely to occur. Genetic drift would weakly increase the likelihood of speciation, due to random changes in genomes likely being different between the two populations, but drift would have a stronger effect of decreasing the chance of speciation, due to increasing the need for genetic variation from migrants. Even though natural selection would select against the traits received from the source population as these individuals are maladapted for the new environment, there would still likely be enough exchange of genetic material to prevent speciation. Therefore, natural selection would increase the probability of speciation, but likely not enough for speciation to actually occur.
gene swamping, critical threshold
knock off adaptive peak, but also probably prevent local extinction

54
Q

role of genetic architecture in the relationship between gene flow and local adaptation?

A

genetic architecture can provide resistance to gene flow via processes like inversion.

55
Q

What role does gene flow play in the maintenance of genetic diversity within populations?

A

gene flow helps prevent fixation by introducing genetic variation

56
Q

Under what conditions should gene flow enhance vs inhibit local adaptation?

A

Enhance when the environment is variable, allowing for adaptation. Inhibit when environment is stable, knocking off adaptive peak.

57
Q

genetic architecture

A

physical genetic basis of phenotypes, such as where genes are located, how they are linked, etc.

58
Q

how does gene flow affect linkage?

A

gene flow can break up linkage if from at least somewhat adapted population, but reinforce it if from maladapted population, as it leads to higher correlations in the matrix

59
Q

how can gene flow be an agent of selection?

A

by spreading advantageous alleles, increasing the genetic variation upon which selection can act

60
Q

adaptive landscape

A

at a population level, relationship between absolute fitness and mean phenotype

61
Q

peak shift

A

jump from a local peak to another local peak or the global peak

62
Q

factors that influence the adaptive landscape

A

environment, intrinsic features of organism, and frequency dependence

63
Q

“proof” of adaptive landscape

A

convergent evolution - distantly related organisms evolving in similar conditions will often evolve to be very similar, even though they evolved independently. The further apart in time, the less likely for convergent evolution, but adaptive landscape still influences organisms’ evolution

64
Q

how might phenotypic plasticity be incorporated into adaptive landscape?

A

can help explain peak shifts, multiple peaks, and fluctuations. phenotypic plasticity can be a trait itself, and selection can favor it

65
Q

what are the challenges of understanding macroevolution with adaptive landscape framework?

A

the time needed for macroevolution is hard to capture with adaptive landscape. However, fluctuations only slow evolution, not stop or change overall direction. Sometimes AL is most helpful tool to think about longterm evolution, as large trends within AL tend to be stable

66
Q

Gmatrix

A

central concept in understanding the inheritance of multiple traits, each of which is affected by many genes, consists of additive genetic variances for the traits on its main diagonal and set of additive genetic covariances between traits (arising from pleiotropy and linkage disequilibrium) as its off-diagonal element

66
Q

Gmatrix

A

central concept in understanding the inheritance of multiple traits, each of which is affected by many genes, consists of additive genetic variances for the traits on its main diagonal and set of additive genetic covariances between traits (arising from pleiotropy and linkage disequilibrium) as its off-diagonal element

Evolution (2 decks)

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