Week 4

Imagine the following genotype frequencies in a population: p2 = 0.49, 2pq = 0.42, q2 = 0.09. Now assume that there is nonrandom mating where individuals with one genotype will only mate with individuals that also have their genotype. Assume this pattern of mating goes on until the frequency of heterozygotes is effectively zero. What will the frequency of allele p be in the population? 0.49 0.91 1.0 0.7 0.3

0.7

Imagine the following genotype frequencies in a population: p2 = 0.49, 2pq = 0.42, q2 = 0.09. Now assume that there is nonrandom mating where individuals with one genotype will only mate with individuals that also have their genotype. Assume this pattern of mating goes on until the frequency of heterozygotes is effectively zero. What will the frequency of allele p be in the population? 0.7 0.91 0.49 0.3 1.0

0.7

Hardy Weinberg Equilibrium

1. There can be no differences in the survival and reproductive success of individuals. 2. Populations must not be added to or subtracted from by migration. 3. There can be no mutation. 4. The population must be sufficiently large to prevent sampling errors. 5. Individuals must mate at random.

Darwin's theory

1. all populations have ability to grow exponentially 2. populations do not grow exponentially (due to selective agents determined by the environment) 3. variation exists within a population (random) 4. the variation must be heritable natural selection only works on heritable traits (positive correlation between parents and offspring)

3 modes of selection

1. directional 2. stabilizing 3. disruptive

Imagine the following genotype frequencies in a population: p2 = 0.49, 2pq = 0.42, q2 = 0.09. Now assume that there is nonrandom mating where individuals with one genotype will only mate with individuals that also have their genotype. Assume this pattern of mating goes on until the frequency of heterozygotes is effectively zero. In addition, there is also inbreeding depression such that individuals with the genotype represented by p2 die before they can reproduce. What will be the frequency of allele q? 0.3 0.91 0.7 1.0 0.49

1.0

Directional selection does not continue in the same direction indefinitely for two primary reasons:

1.Environmental change: 2. Developmental constraints and/or selective trade-offs: - a given trait will eventually reach a point where it can't get any bigger or smaller

If a gene has two alleles, and allele A has a frequency of 83%, then allele a has a frequency of: 7%. 117%. 166%. 41.5%. 17%.

17%.

In a population of Mendel's garden peas, the frequency of the dominant A (yellow flower) allele is 80%. Let p represent the frequency of the A allele and q represent the frequency of the a allele. Assuming that the population is in Hardy-Weinberg equilibrium, what are the genotype frequencies? 80% AA, 10% Aa, 10% aa 75% AA, 15% Aa, 10% aa 50% AA, 25% Aa, 25% aa 16% AA, 40% Aa, 44% aa 64% AA, 32% Aa, 4% aa

64% AA, 32% Aa, 4% aa

Suppose that kin selection is acting upon a group of rodents. The average female typically has four offspring in her lifetime. If, instead of raising her own offspring, a female helps her sister raise her offspring (i.e. her own nieces and nephews). How many offspring would her sister have to have in order for her to experience no net loss in fitness? 8 10 4 12

8

In a population of Mendel's garden peas, the frequency of green-flowered plants (genotype aa) is 49%. The population is in Hardy-Weinberg equilibrium. What are the frequencies of the AA and Aa genotypes? 49% AA, 2% Aa 33% AA, 18% Aa 42% AA, 9% Aa 9% AA, 42% Aa The frequencies cannot be determined from the information provided.

9% AA, 42% Aa

You are given the following information about a population: • There are two alleles: C and c. • C codes for green hair and c codes for white hair. • C is dominant over c. • The frequency of the c allele is 0.3. • The population is comprised of 100 individuals. Assuming the population is in Hardy-Weinberg equilibrium, how many individuals have green hair? 9% of the population will have green hair. 91% of the population will have green hair. 51% of the population will have green hair. 49% of the population will have green hair.

91% of the population will have green hair.

genetic drift Drift tends to reduce genetic variation - the extent to which it does this is dependent upon population size (drift has a stronger effect on smaller populations), not on the existing amount of variation.

A change in the frequency of an allele due to the random effects of limited population size is called genetic drift. In each generation, some individuals may, just by chance, leave behind a few more descendents (and genes, of course!) than other individuals. The genes of the next generation will be the genes of the "lucky" individuals, not necessarily the healthier or "better" individuals. That, in a nutshell, is genetic drift

Consider a population of killer whales. The gene pool of this population would only contain alleles harboring beneficial or neutral mutations, as deleterious mutations are efficiently eliminated from the gene pool of a species. False True

False

Traits favored by sexual selection are the same traits favored by natural selection. True False

False

Hardy Weinberg principle shows that evolution is not happening

Genotypes: AA Aa aa genotype frequencies: p^2 + 2pq + q^2 = 1 Genotypic frequency shifts with your allele frequency

Which of the following is NOT a condition of the Hardy-Weinberg equilibrium? Mutations cannot occur in a population. Mating within a population must be random. Individuals of any genotype must have the same reproductive success as individuals of any other genotype. Individuals can migrate in and out of a population, as long as the population size remains constant. The size of a population must be large.

Individuals can migrate in and out of a population, as long as the population size remains constant.

sexual selection

Male trait & female preference passed down both maternal & paternal lines For sexual dimorphism to work out, you have got to have the allele in both genders- both need to have it because they only give 1 allele each to their kid when you introduce predators to the mix, the showiness of the trait goes down because you have interplay between sexual selection and natural selection

how do we know if a population is evolving?

Microevolution: Change in allele OR genotype frequencies in a population over one or more generations Macroevolution: Basically the same thing, except over a period of time long enough to allow for substantial phenotypic change

Why is it thought that the majority of natural selection is stabilizing selection? Directional selection is more common because it increases adaptations to the environment. Most mutations are beneficial and produce intermediate phenotypes. Artificial selection is the most common, which is a type of stabilizing selection. Most mutations are deleterious and produce an extreme phenotype that is selected against. Mutations produce extreme phenotypes, which are selected for.

Most mutations are deleterious and produce an extreme phenotype that is selected against.

sources of genetic variation

Mutations, recombination, independent assortment , you don't know which gamete will succeed

Imagine the following genotype frequencies in a population: p2 = 0.49, 2pq = 0.42, q2 = 0.09. Now assume that there is nonrandom mating where individuals with one genotype will only mate with individuals that also have their genotype. Assume this pattern of mating goes on until the frequency of heterozygotes is effectively zero. Is this population in Hardy-Weinberg equilibrium? Yes, because allele frequencies did not change. No, because there is nonrandom mating. No, because allele frequencies changed. Yes, because there is not inbreeding depression.

No, because there is nonrandom mating.

Malthus pointed out that populations have the potential to increase geometrically. What did this observation suggest that contributed to the idea of natural selection? Populations may grow faster than their resources. Populations may grow quickly, and then will evolve more quickly. Populations grow quickly, but predators grow more quickly. Populations may grow quickly and spread out over the planet. Populations may grow faster than other competing populations.

Populations may grow faster than their resources.

Inbreeding depression is a serious concern in small populations of endangered organisms. Why is inbreeding depression a concern for such populations? Related individuals are more likely to mate with one another and this will increase the frequency of heterozyous genotypes. Related individuals will not mate with one another, and this increases the probability that two deleterious alleles will be present when unrelated individuals mate. Related individuals are more likely to mate with one another and this increases the probability that two deleterious alleles will be present in the offspring. Related individuals will not mate with one another, therefore population number will decline.

Related individuals are more likely to mate with one another and this increases the probability that two deleterious alleles will be present in the offspring.

Why does genetic drift have more of an impact on the evolution of small populations than large ones? Sampling from generation to generation is more variable in small populations than large. Small populations are less affected by mutations. Small populations are more prone to migration. Small populations are affected more by stabilizing selection. Small populations have greater rates of mutation.

Sampling from generation to generation is more variable in small populations than large.

Prior to the publication of Darwin's On the Origin of Species, people thought what about species? Species changed over time because they were not adapted to their environment. Species evolved at one point, but no longer changed because they were not adapted to their environment. Species were designed already perfectly adapted to their environment. Species changed over time as guided by a divine creator.

Species were designed already perfectly adapted to their environment.

Which mode(s) of selection will not necessarily change the mean trait value in a population?

Stabilizing Disruptive

Why can't we measure genetic variation in a population using observable traits (phenotypes)? (Select all that apply.) The environment can also affect the phenotype. Many traits are encoded by multiple genes. All traits are encoded by a single gene. Phenotypes are not determined by genes.

The environment can also affect the phenotype. Many traits are encoded by multiple genes.

What is the result of a mutation that occurs in somatic cells? The mutation will prevent all reproduction. The mutation may be expressed in the individual, but will not be passed along to its offspring. There will never be any visible effect. The mutation will be passed along to the organism's offspring. The mutation will be deleterious.

The mutation may be expressed in the individual, but will not be passed along to its offspring.

As a population geneticist, you find a species of snails with more genetic diversity than humans. What does this mean? There is not enough information provided to answer this question. The snails have more DNA than humans. The snails have more mutations occurring than humans. There is more variety in the gene pool of snails than humans. The snails have more genes on their chromosomes than humans.

There is more variety in the gene pool of snails than humans.

In a given population, all humans have the same blood type O. If no other alleles for blood type exist in this population, this population is "fixed" for the O allele. False True

True

Mutation increases genetic variation. False True

True

Evolution is both random and non-random

True random: whats good enough goes forward non-random: we get rid of things we don't need through evolution

A gene that no longer retains function is called: a pseudogene. a terminal gene. negatively selected. a gene with a stopped molecular clock. broken.

a pseudogene

If two populations are thought to be diverging from one another, what would you expect to observe? an increase in similarity of alleles coding for proteins the same genotypes, but different phenotypes an accumulation of different mutations in different populations more shared mutations in different populations

an accumulation of different mutations in different population

Kin selection

behavior by individuals that may decrease their chance of survival but increases that of their kin (who share a proportion of their genes) ie: give up having kids because your really related to your sisters Haplo-diploid systems have sisters that are more related to each other than they are to their mother! There are other organisms known for altruistic behavior that don't have the haplo-diploid system Reciprocal altruism- I'll do something nice for you now, and you'll do something for me later

If a population is not in Hardy-Weinberg equilibrium, we can conclude that: All of these choices are correct. evolution has occurred because one or more of the assumptions of the Hardy-Weinberg equilibrium has been violated. natural selection has occurred. one of the assumptions of the Hardy-Weinberg equilibrium has been violated. nonrandom mating has occurred.

evolution has occurred because one or more of the assumptions of the Hardy-Weinberg equilibrium has been violated.

If a population is not in Hardy-Weinberg equilibrium, we can conclude that: nonrandom mating has occurred. All of these choices are correct. natural selection has occurred. evolution has occurred because one or more of the assumptions of the Hardy-Weinberg equilibrium has been violated.

evolution has occurred because one or more of the assumptions of the Hardy-Weinberg equilibrium has been violated.

Migration reduces genetic differences between populations by allowing gene _____ between the two. repression drift flow augmentation deletion

flow

You are researching a population of moles. In the course of your research, you identify a nearby population that occasionally comes into contact with your study population. What BEST describes the evolutionary process at work? genetic drift natural selection artificial selection gene flow mutation

gene flow

All the alleles present in all individuals in a species are referred to as the _____ of that species. allele frequency gene pool genotype genotype frequency phenotype

gene pool

What term CORRECTLY describes change in allele frequency due to random effect of a small population? nonrandom mating mutation selection genetic drift immigration

genetic drift

Endangered species with very small populations are especially at risk of loss of genetic diversity due to: immigration. mutation. natural selection. genetic drift.

genetic drift.

fitness

how many offspring you leave in the next generation Direct fitness: # of kids you have X relatedness (1/2) (if your diploid and give half your genes to next generation) 3 kids (1/2) = 1.5 Indirect fitness: siblings X relatedness + siblings kids X relatedness Inclusive fitness= direct + indirect fitness

Assortative Mating

mating pattern and a form of sexual selection in which individuals with similar phenotypes mate with one another more frequently than would be expected under a random mating pattern

There are other mechanisms that can cause allele and genotype frequencies to change. These are :

migration, mutation, genetic drift, and non-random mating.

The correlation between the time two species have been evolutionarily separated and the amount of genetic divergence between them is known as the: molecular clock. Modern Synthesis. natural selection. artificial selection. Hardy-Weinberg equilibrium.

molecular clock.

Some proteins have a slower molecular clock due to _____ selection, which eliminates harmful alleles. disruptive negative positive beneficial neutral

negative

For reciprocal altruism to work, individuals must be able to: calculate the fitness value of individual interactions. recognize one another. remember previous interactions. recognize one another, remember previous interactions, and calculate the fitness value of individual interactions. recognize one another and remember previous interactions.

recognize one another and remember previous interactions.

Genetic variation has two sources-mutation and: non-random mating. recombination. natural selection. cell division. genetic drift.

recombination

Balancing Selection

refers to a number of selective processes by which multiple alleles are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone ie: sickle cell trait note:stabilizing selection refers to phenotypes, whereas balancing selection is all about alleles and genotypes

Which of the following is an example of stabilizing selection? decrease in the number of birds with intermediate-sized beaks who are unable to eat large or small seeds breeding dogs from wolves antibiotic resistance in bacteria selection for average birth weight in humans

selection for average birth weight in humans

Group selection is not typically seen as an evolutionarily stable strategy because: it cannot explain behaviors for species with solitary individuals. None of the answer options is correct. selfish behaviors are more likely to increase individual fitness. average relatedness is very low between individuals in a population, therefore individual fitness cannot increase.

selfish behaviors are more likely to increase individual fitness.

The intricate plumage of male birds of paradise has become increasingly elaborate throughout their evolution due to females mating preferentially with males that display the most impressive feathers. This is an example of _____ selection. stabilizing disruptive sexual artificial

sexual

selective agent

something that sterilizes or kills you

The goldenrod gall fly lays its eggs on the terminal buds of goldenrod plants. Larvae chew through the buds and into the stems, where their saliva induces the plant to generate a gall, or outgrowth of tissue that then provides food and shelter for the developing larva. The larvae are prey to both parasitoid wasps and to birds; wasps selectively prey on larvae inside the smallest galls while birds selectively prey on larvae inside the largest galls. Goldenrod gall flies are therefore subject to _____ selection. stabilizing balancing disruptional heterozygote directional

stabilizing

Two populations that have been separated from each other for a long period of time will have: small differences in phenotype but identical genotypes. limited differences between their genetic sequences. substantial differences between their genetic sequences. no similar genetic sequences. no differences between their genetic sequences.

substantial differences between their genetic sequences.

Meerkats are small desert mammals that live in groups of 20-50 individuals. You observe one meerkat standing upright on a stump, looking around, while other meerkats forage for food. You hypothesize that this is an example of kin selection. What additional information would you need to know to evaluate your hypothesis? the degree of genetic relatedness of this meerkat to all members of the group the body size of this meerkat relative to other members of the group all other activities of this meerkat as well as those of all other members of the group the gender of this meerkat as well as that of all other members of the group the foraging success of this meerkat as well as that of all other members of the group

the degree of genetic relatedness of this meerkat to all members of the group

What does the term 2pq represent in the Hardy-Weinberg relation? the frequency of homozygous dominant individuals the frequency of deleterious mutations the frequency of homozygous recessive individuals the frequency of heterozygotes

the frequency of heterozygotes

If B = the benefit of a behavior to a recipient, C = the cost of the behavior of the donor, and r = the degree of relatedness between the recipient and donor, then if rB > C, altruism can evolve. True False

true

Sexual dimorphism

when males and females looks different (ex: humans) distinct difference in size or appearance between the sexes of an animal in addition to difference between the sexual organs themselves