Exam 1

Question 1

Darwin’s postulates

Answer 1

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)

Question 2

Modern Synthesis

Answer 2

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.

Question 3

Evolutionary genomics

Answer 3

sequencing entire genomes

Question 4

Group selection

Answer 4

for the good of the group

Question 5

Holes in modern synthesis?

Answer 5

Epigenetics, evolutionary developmental biology, meta organisms, prokaryotes

Question 6

Epigenetics

Answer 6

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

Question 7

evo-devo biology

Answer 7

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

Question 8

How does evo-devo clash with modern synthesis?

Answer 8

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.

Question 9

meta-organisms

Answer 9

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).

Question 10

natural selection

Answer 10

variation in relative fitness within a population

Question 11

absolute fitness (individual)

Answer 11

the number of offspring produced by that individual in its lifetime

Question 12

absolute fitness (population)

Answer 12

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

Question 13

relative fitness (individual)

Answer 13

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

Question 14

Selection differential (S)

Answer 14

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

Question 15

univariate breeder’s equation

Answer 15

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

Question 16

fitness landscape

Answer 16

relationship/covariance between trait value and relative fitness

Question 17

multivariate breeder’s equation

Answer 17

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)

Question 18

Selection model terms

Answer 18

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

Question 19

linear terms

Answer 19

test for positive and negative directional selection on trait means

Question 20

non-linear - univariate

Answer 20

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

Question 21

non-linear - bivariate

Answer 21

test for correlational selection on pairs of traits

Question 22

what does positive correlational selection mean for the trait values?

Answer 22

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

Question 23

neutral theory

Answer 23

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

Question 24

narrow sense heritability (h^2)

Answer 24

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

Question 25

h^2=

Answer 25

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

Question 26

epistasis

Answer 26

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.

Question 27

non-additive genetic variance

Answer 27

dominance, epistasis

Question 28

Ve=

Answer 28

environment, genotype (plasticity)

Question 29

Vp=

Answer 29

Va+Vna+Ve

Question 30

Why do we only care about additive genetic effects?

Answer 30

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

Question 31

What are the proximate causes of genetic correlations?

Answer 31

linkage disequilibrium, pleiotropy

Question 32

linkage disequilibrium

Answer 32

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

Question 33

pleiotropy

Answer 33

one gene influences two or more seemingly unrelated phenotypic traits

Question 34

what is the ultimate cause of genetic correlations?

Answer 34

correlational selection

Question 35

Gmax

Answer 35

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

Question 36

genetic drift

Answer 36

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

Question 37

gene flow

Answer 37

movement of genes across space from one population to another

Question 38

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

Answer 38

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

Question 39

mutation-selection balance

Answer 39

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

Question 40

population bottleneck

Answer 40

sudden drop in population size that noticeably alters allele frequency

Question 41

inbreeding depression

Answer 41

deleterious alleles increasingly combined into homozygous genotypes

Question 42

background selection

Answer 42

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

Question 43

founder effect

Answer 43

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

Question 44

positives of founder effect

Answer 44

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

Question 45

shifting balance model

Answer 45

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

Question 46

positives of gene flow

Answer 46

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

Question 47

cons of gene flow

Answer 47

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

Question 48

gene swamping

Answer 48

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

Question 49

migration selection balance

Answer 49

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

Question 50

genetic rescue

Answer 50

gene flow can provide small populations with fresh genetic variation

Question 51

evolutionary rescue

Answer 51

new mutation rescues a small, deleterious allele-filled population

Question 52

forces of evolution

Answer 52

mutation, natural selection, gene flow, genetic drift

Question 53

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?

Answer 53

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

Question 54

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

Answer 54

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

Question 55

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

Answer 55

gene flow helps prevent fixation by introducing genetic variation

Question 56

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

Answer 56

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

Question 57

genetic architecture

Answer 57

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

Question 58

how does gene flow affect linkage?

Answer 58

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

Question 59

how can gene flow be an agent of selection?

Answer 59

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

Question 60

adaptive landscape

Answer 60

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

Question 61

peak shift

Answer 61

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

Question 62

factors that influence the adaptive landscape

Answer 62

environment, intrinsic features of organism, and frequency dependence

Question 63

"proof" of adaptive landscape

Answer 63

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

Question 64

how might phenotypic plasticity be incorporated into adaptive landscape?

Answer 64

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

Question 65

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

Answer 65

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

Question 66

Gmatrix

Answer 66

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

Question 66

Gmatrix

Answer 66

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