BIO370 Exam 2 Study Questions

A new, neutral mutation (s=0) arises in a small population of 1000 fruit flies living under ideal conditions in a laboratory (i.e., not under selection). What is the probability that the allele will ultimately go to fixation (i.e., reach a frequency of 1.0)?

For a new neutral mutation (s=0), the probability of fixation is equal to an allele's current frequency. If p=0.5, chance of fixation or loss is 0.5 OR 1/2(1000) = 0.0005

measures divergence in neutral genetic marker

Fst

How does QST relate to FST? Describe how you would collect data to determine each of these values.

Fst: measures divergence in neutral genetic markers. Qst measures divergence in quantitative traits. if Qst=Fst, neutral trait, no spatially divergent selection on the trait, differentiation in Qst explained by genetic drift, gene flow balance alone. Qst>Fst, trait has diverged more than would be expected by genetic drift-flow balance alone, divergent selection may underly phenotypic divergence among populations Qst<Fst, stabilizing selection may be acting to maintain the phenotype across populations

sex can reconstitute mutation free state, sex can also remove mutations because recombination can produce individuals with MANY deleterious mutations, these are removed by strong selection, purge the population of mutations

Koharshov's hatchet

types of transposons

LINEs, SINEs, DNA transposons, Retrotransposons

measures divergence in quantitative traits

Qst

How does sexual reproduction speed up adaptive evolution? Describe with words or with a drawing.

Whereas asexual organisms have to wait for consecutive advantageous mutations to occur in a single lineage, sexual organisms can recombine and bring together favorable mutations. Segregation can bring together 2 copies of a good mutation at a single locus, recombination can also bring together good mutations at two different loci. It also helps for when an advantageous mutation can be trapped by deleterious mutations. (recombination negates the ruby in the rubbish effect)

males success is usually limited by what

access to mates

two main categories of hypotheses that explain why organisms age and die

accumulation of damage theories and evolutionary theories

a behavior that benefits/increases the fitness of another at the expense of the actor

altruism

beneficial in a constant environment according to the lottery-bet hedging model

asexual

explain the notion that sex speeds up adaptive evolution

asexuals have to wait for consecutive advantageous mutations to occur in a single lineage, sexual organisms can recombine and bring together favorable mutations

what does hemagglutinin do

binds to sialic acid on host cells, virus enters cell

what does AZT do

blocks active domain in reverse transcriptase of HIV

Describe the simplified equation predicting the change in allele frequency from one generation of selection. How does the response to selection change with allele frequency?

change in p=p(1-p)s. response to selection will be highest when allele frequency is intermediate (0.50 yields 0.25 as change in p) higher or lower than 0.5 will decrease the response to selection

ideal population

constant, no selection, all individuals have the same chance of leaving offspring

A man returns to Austin after a trip around the globe, and succumbs to some novel strain of avian flu. Describe how you could apply phylogenetic methods to track down the geographical source of the virus.

create a phylogenetic tree to determine the most recent ancestor. where does the new flu fit on the tree- determine by counting the number of like mutations

pros of irrational design

creation of huge amounts of novel variation, dont have to understand the mechanism

limits to bet-hedging/lottery models

data shows the opposite. tropics: stable, lots of sexual organisms. artics: variable, lots of asexual organisms

limitations to the speeding of adaptive evolution

depends on the rate of beneficial mutations, if they happen frequently, wait time may not be long enough to matter

limits to red queen hypothesis

depends on very strong selection, parasites can select for clonal diversity rather than sex

two different types of evolutionary forces

deterministic and stochastic

fitness through production of own offspring

direct

findings of fitch's experiment

divergence has occurred at a rate too rapid to be explained by genetic drift

1/Ne >> s

drift much stronger, selection can be ignored

number of indidividuals in an idealized population that would have the same intensity of random genetic drift

effective population size

Define effective population size. Provide two examples of situations that would cause the effective population size to be smaller than the census population.

effective population size is the number of individuals in an idealized population that would have the same intensity of random genetic drift. changes in N through time because of genetic bottleneck, or population subdivision (founding effect) or an unequal number of males and females

high reproductive effort, very costly to reproduce

female function

proof that female mating preference evolves

females of different species have different preferences, genetic variation in preference has been directly measured, artificial selection can change preferences

Verbally describe the process of Fisher's "runaway" evolution of male display and female preference. Describe two forces that could limit Fisherian runaway

fisher's runaway describes the linkage disequilibrium between female preference and male display. This does not denote physical gene linkage. the male trait becomes amplified to the point where the it becomes detrimental. two forces that could limit: if the population went back to random mating, runaway would stop and covariation would decrease. if the genetic variability goes away, the trait would become fixed and the runaway would be bounded.

Describe a scenario depicting how gene flow can prevent local adaptation. Similarly, describe a scenario depicting how gene flow can promote adaptive evolution.

gene flow preventing local adaptation: when gene flow is acting as a homogenizing force, constantly blending populations, for example in the mine plants. gene flow promoting local adaptation: if there was no variation to start out with

What effect does genetic drift have on the distribution of genetic variation within and among populations? What effect does gene flow have on genetic variation within and among populations?

genetic drift generates heterogeneity among populations and causes genetic variation to be lost over time within populations because one allele will ultimately become fixed. gene flow is a homogenizing force between populations, meaning it decreases genetic variation among populations. In some cases it can increase within population variation if the gene flow introduces new genetic variation to a population.

indirect selection on preference genes

good genes hypothesis

example of direct selection on preference genes

good territory, nupital gifts, help with parental care

three tradeoffs in life history

growth, maintenance, reproduction

predominant coat protein of influenza

hemagglutinin

Describe Hamilton's kin selection model for the evolution of altruistic behavior.

if rB > c you would expect a mutation that favors the evolution of altruistic behavior. r= relatedness of actor/recipient. B= fitness benefit to recipient c= cost to actor

What is Muller's ratchet?

in asexual organisms, there is an accumulation of deleterious mutations over time, the mutation free individuals lost by genetic drift. once lost, they are lost forever

fitness through effects of relatives

indirect

approach that relies on selection to reach outcome

irrational design

selection favoring behavior between individuals that share genes through kinship

kin selection

What is linkage disequilibrium? Give a specific example of how it can play an important evolutionary role

linkage disequilibrium is the statistical correlation between alleles at two or more loci that differ from those expected based on frequency of alleles in a particular population. example: fischers runaway model

problems with the wear and tear hypotheses

living organisms have the ability to regenerate, use often related to increased quality, aging resembles an evolved trait- vast differences among even closely related species

why do females choose what they choose?

male signaling

In your own works, define the "good genes" hypothesis. Describe an experiment to test the "good genes" model of the evolution of female preference.

males with good genes are healthier and can devote more resources to appearance and displays, may have offspring with the best chances of reproductive success. indirect selection. design an experiment with sibships, 2 offspring that have the same mom but different dads, sibships control for maternal genes. this allows us to see the effect of the male genes

there is a huge variability in reproductive success in ______ populations, but there is not in __________ populations

males, females

how much time and energy it takes you to find a mate

mating effort

any aspect of the female that biases the kind of mate she chooses, does not require cognition

mating preference

list the order of the hierarchy of units on which selection can act

molecules, organelles, individuals, kin/group selection

Provide two examples demonstrating the fact that patterns of selection depends on environmental context.

moth and sickle cell anemia

a mutation that causes death later in life may have very little impact on an organism's lifetime reproductive success

mutation accumulation

two evolutionary theories on why organisms age and die

mutation accumulation, tradeoff hypothesis

Why do organisms die? Provide at least two plausible hypotheses based on evolutionary theory.

mutation accumulation: a mutation that causes death later in life (after reproduction) may have very little impact on an organism's lifetime reproductive success. the later in life mutations exert bad effects, the more weakly they are selected against. trade off hypothesis: mutations may occur that involve a pleiotropic tradeoff between reproduction early and survival later in life. any mutation favoring reproductive success early should be favored, even if it has detrimental effects later in life.

late acting deleterious genes should accumulate at many different loci, making prospect of finding single aging gene impossible

mutation balance selection theory

name the three types of deterministic evolutionary forces

mutation, natural selection, gene flow

name the five evolutionary forces

mutation, selection, random genetic drift, gene flow, mating system

challenges of irrational design

need variation, need replication, need differential selection/screening scheme

Five Hardy-Weinberg Conditions

no selection, no gene flow, no mutation, random mating, large population size

when spread of virus is rapid, high virulence okay or not okay

okay

engineer new function base on knowledge of how a molecule works

rational design

cooperation can evolve as long as favors are returned, this can evolve through individual selection level, benefit must outweigh the cost

reciprocal altruism

hypothesis that says sex is needed to fight disease, constant arms race between the host and parasites, genotype cycling, sex advantageous because recombination produces novel combinations

red queen hypothesis

sexes can be defined as a tradeoff between what two things?

reproductive effort and mating effort

female success is limited to what

resource availability

when a chromosome with no deleterious mutations has higher fitness than the one with the beneficial one and deleterious mutation

ruby in the rubbish effect

1/Ne << s

selection much stronger, drift can be ignored

every cell has multiple copies of the chloroplast and mitochondria genomes, genomes compete against each other

selection on organelles

female preference is simply a side effect of sensory evolution which has evolved for other reasons

sensory bias

divison of soma vs. germ cells

sequestration of cells that are to be making your gametes, soma constantly dividing and at some point there is a limit, that is why the germ line is sequestered

name the ecological theories of why sex is beneficial

sex helps cope with variable environment (lottery-bet hedging models, red queen hypothesis)

may have been more important for the origin of sex, less important in terms of maintenece of sex

sex required for DNA repair

the three genetic hypotheses that explain sex

sex required for DNA repair, sex speeds up adaptive evolution, sex can purge deleterious mutations

differential/nonrandom reproductive success due to ability to obtain mates, frequency dependent, doesn't fit fischers model

sexual selection

Name two different mechanisms by which male-male sexual selection works. Give an example of each

sperm competition- make more sperm, block destroy other males' sperm. (dragonflies, flies, butterflies the male scoop out previous sperm, male reproductive organ breaks off and stays in the female so that no other males can fertilize her) infanticide- males kill juveniles of a species so that female finishes lactating and is able to go back to being pregnant. (in lions, infanticide results in 10% of all lion mortality)

how do preferences evolve?

stabilizing selection between sexual selection and natural selection

as you accumulate mutations, there is a buffering to some point and then you reach a certain point where there is a huge packing together of deleterious mutations, selection would purge the population of deleterious mutations

synergistic epistasis

may be related to cancer and processed cell death

telomere shortening

What determines the strength of genetic drift in nature? How does the strength of drift impact the maintenance of genetic variation?

the effective population size determines the strength of genetic drift in nature. small effective population size leads to strong drift, less likely to maintain diversity. large populations more likely to maintain genetic diversity.

limitation to purging deleterious mutations hypthesis

the ratchet works slowly, depends on mutation rate, population size, selection. the hatchet depends on epistatic selection, should be important in effective population sizes with high mutation rates

What are two main types of sexual selection? How do they differ?

the two main types of sexual selection are intrasexual selection (male-male competition) and intersexual selection (female choice). male male competition- sex with lower parental investment will show greater mating effort, leads to competition in access to mates. female choice- sex with higher parental investment will be choosy in mate selection

Describe three possible costs of sexual reproduction.

there is a two fold cost of sex (females contribute most of the resources by only half the genes, males contribute half the genes but essentially no resources, a female would be able to transmit twice as many genes for the same price of offspring), finding a partner can be a problem, STDs, sex breaks up good combinations of genes

Sewall Wright argued that the interplay of random genetic drift, natural selection, and gene flow would have the best chance of leading a species to a global fitness peak. What did Wright name this process? Give a verbal description of adaptive evolution through this process. What will determine the whether peak shifts can happen?

this is the shifting balance theory. a species divided in subpopulations small enough that random genetic drift important. drift in one subpopulations carries it past an adaptive valley to a new adaptive peak. this subpopulation has increased fitness. it makes more offspring, which spread the new adaptation to other populations through increased gene flow. flip over adaptive landscape. genetic drift moves the ball left and right randomly, allowing peak shift.

mutations may occur that involve a pleiotropic trafe off between reproduction early and survival late in life

trade off hypothesis

Describe one scenario where selection may be in conflict across levels of biological organization.

transposons: DNA sequences that code for their own replication within the genome. can copy itself and insert into other places in the genome, major source of deleterious mutations. selection for transposons with the highest fitness but also selection at the higher level against deleterious mutations

What are the key pieces of data required to test the sensory bias hypothesis for the evolution of female preference?

you need a phylogenetic tree so that you can determine whether the female preference trait or the male display trait appeared first

specific parts of the protein recognized and remembered by the immune system

antigenic sites

inclusive fitness

direct + indirect

probability that the other individual carries a rare gene that you have

relatedness

energy it takes to have offspring

reproductive effort

Why might sex be valuable in a variable environment?

this is from the lottery/bet-hedging models, sexual reproduction includes lottery tickets with many different numbers, if environment if variable, this is more beneficial

You recently joined a team that is creating a booklet of strategies to help disadvantaged farmers in Indonesia effectively spray their crops with multiple pesticides. What are some strategies you include in the booklet and why?

use the method of refugia to control increase in resistance. tell them to not plant 100% of the crops with the pesticides, make sure there is 20% that hasn't been exposed to pesticides. dilute and keep resistance insects from being selected for

problems with evolutionary theories that explain aging

why differences among species, why exponential decline, why genes of major effect rather than minor

gene that increases survival but decreases reproduction

antagonistic pleiotropy

accumulation of damage theories

cell division limit, programmed death, rate of life, waste/accumulation/free-radical damage

using evolutionary processes to engineer new chemicals, molecules, or organisms for particular use

directed evolution

may cause a species to move downhill on an adaptive landscape because it causes random fluctuations in allele frequencies

genetic drift

name the stochastic evolutionary force

genetic drift

random changes in gene frequencies due to sampling error

genetic drift

What effect will random genetic drift have on populations that initially are genetically similar?

genetic drift generates heterogeneity among populations

Selection is expected to drive deleterious mutations to extinction in natural populations. Nonetheless, deleterious mutations exist (sometimes in high frequency) in natural populations. Give an explanations for why this might occur.

if there is linkage on a chromosome, good and bad genes might be passed on together. pleiotropic tradeoff. muller's ratchet. deleterious mutations that dont have an effect until after reproductive age

high mating effort, low reproductive cost

male function

when spread of virus is rare, high virulence okay or not okay

not okay

heterozygote has the highest selection

overdominance

selection against the heterozygote

underdominance

usually takes a species ____ to evolve

2 years