Bio 345 Exam 2
frequency-dependent selection
An individual's fitness depends on the behavior (and the frequency of the behavior) of others.
What is neoteny? A. A trait that appears over and over again B. A new small character C. A martial arts move from the Matrix D. A trait retained from an ancestor E. A juvenile trait retained into adulthood
E. A juvenile trait retained into adulthood
Which situation would represent a trade-off between survival and reproduction? A. Mating activity and egg production reduce the longevity of both sexes B. Survival to greater age comes at the expense of early reproduction C. Human parents have less sleep and higher rates of disease infection than nonreproductive individuals D. The production of many offspring results in smaller offspring E. All of the above
E. All of the above
Which of the following describes a coevolutionary relationship? A. The gazelle population of the savannah has evolved quick speed because faster gazelles have escaped predation and bred more than slower gazelles. B. Squirrels in areas with pinecones have evolved stronger jaws than squirrels in areas without pinecones. C. Both finches and parrots are selected for deeper, stronger beaks in years when only large, hard seeds are available. D. All of the above describe coevolutionary relationships. E. None of the above, on its own, describes a coevolutionary relationship
E. None of the above, on its own, describes a coevolutionary relationship
Populations of some species of fish, insects, and crustaceans consist of both sexually and obligately asexually reproducing individuals. 1) Would you expect such populations to become entirely asexual or sexual?
Entirely asexual populations of animals are rare.The cost of sexual reproduction is considered to be twice that of asexual reproduction, because sexual females produce ≈ 50% male offspring, and males typically contribute only their genes to reproduction (Maynard Smith, 1978). Following this logic, asexual reproduction should dominate unless there is greater than a two-fold advantage to sexual reproduction.
game theory
Evaluates alternate strategies when outcome depends not only on each individual's strategy but also that of others.
example of the cost of reproduction
Evidence of the cost of reproduction. (A) Female Anolis sagreifrom which ovaries were removed (OVX) grew larger and gained more weight than sham-operated (SHAM) females. SVL is the snout-to-vent length. (B) Over the 2-year study, the proportion of females that survived to the following year was higher for ovariectomized females (blue columns) than for sham-operated females (red columns), which produced eggs. Allocation to reproduction reduced females' growth and survival
Why is explaining altruistic behavior an important challenge for evolutionary theory?
Evolution = traits the benefit the actors fitness Altruistic behavior doesn't benefit the actor, but it protects the relatives with similar alleles ex. vampire bats that have fed will feed a hungry bat -this is an example of reciprocation (tit for tat), group selection (good for the colony), preserves the gene pool ( group selection argument). The bats could be related (inclusive fitness) and could be connected with dynamic of dynamic of diminishing returns (cost vs benefits).
ruby in the rubbish effect (a form of selective interference) : which is the loss of beneficial mutations as the result of their linkage to deleterious mutations
Experiments with yeast (Saccharomyces cerevisiae) show how recombination speeds adaptation. This species can be manipulated in the lab to reproduce either sexually or asexually. (A) After 1000 generations of adaptation to a laboratory environment, the fitness of the sexual populations increased about twice as much as that of the asexual populations. (B) DNA sequencing at different time points followed the frequencies of mutations spreading in an asexual and a sexual population. Separate experiments were used to estimate the fitness effects of those mutations. The trajectories of beneficial mutations are shown in green, and of deleterious mutations in purple. In the asexual populations, eight beneficial mutations had become fixed by the end of the experiment. As they did so, they dragged five deleterious mutations to fixation with them. In the sexual populations, recombination freed the beneficial mutations from the deleterious ones. As a result, all of the deleterious mutations were eliminated.
eusocial
organism population in which the role of each organism is specialized and not all of the organisms will reproduce A. several species of naked mole-rats, here Heterocephalus glaber, are the only known eusocial mammals. (B) This queen termite is attended by small, sterile workers and large-headed, sterile soldiers. (C) Australian honeypot ants (Camponotus inflatus), engorged with nectar, hang from the roof of their nest's larder. These "repletes" regurgitate nectar on demand to their worker nestmates. (D) Paper wasps (Polistes gallicus) at their nest.
Table A more offspring early on, so offspring can also reproduce
For species evolving under r selection, which hypothetical life history below would be it better to have? Table A Table B
reproductive success
(R) is the probability of a female's survival to age x (lx) multiplied by the average fecundity at age x (mx); or R = Σ lxmx
non-synonymous mutation
a nucleotide mutation that alters the amino acid sequence of a protein
Anisogamy likely evolved because gametes can reach high fitness in two ways:
1) Gametes can be large and well provisioned, but movement is inhibited. 2) Gametes can be small and mobile, enhancing the ability to find the large immobile gamete.
Anisogamy likely evolved because gametes can reach high fitness in two ways:
1) Gametes can be large and well provisioned, but movement is inhibited. 2) Gametes can be small and mobile, enhancing the ability to find the large immobile gamete.
Elephants have very low cancer rates, despite their size and long lives. Humans have 1 copy of TP53 gene ( makes p53 tumor suppressing protein), how many copies does an elephant have?
20
Morran et al. 2013 did three experiments to see how the Red Queen Hypothesis affected the rate of outcrossing. They measured outcrossing rates in C. elegans populations evolved: 1. Without parasite (control) 2. With fixed parasite (evolution) 3. With coevolving parasite (coevolution). Which experiment should show the lowest rate of outcrossing given the cost of sex? 1. Without parasite (control) 2. With fixed parasite (evolution) 3. With coevolving parasite (coevolution)
3. with coevolving parasite
Genome composition.. only___ % codes for proteins, and ___% is conversed by natural selection
92% of the genome's purpose is not well understood
The reproductive fitness of a group should be measured by A) The number of groups it produces B) The growth rate of the group C) How long the group lasts D) The number of offspring its members produce that grow to reproductive age
A) The number of groups it produces
What is an adaptation?
A derived character that conferred higher fitness than the ancestral character state from which it evolved •A process of genetic change in a population whereby, as a result of natural selection, the average state of a character becomes improved with reference to a specific function, or whereby a population is thought to have become better suited to some feature of its environment. •A feature that has become prevalent in a population because of a selective advantage conveyed by that feature in the improvement in some function.
Karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
synonymous (silent) mutation
A mutation resulting in a codon that does not alter the corresponding amino acid in the polypeptide.
Prisoner's Dilemma
A situation in which two (or more) actors cannot agree to cooperate for fear that the other will find its interest best served by reneging on an agreement. Debt based rule
escape and radiate coevolution
A species evolves a defense against enemies and is enable to radiate into a diverse descendant species.
Many species of animals make "alarm calls," which warn others in their group that a predator is approaching. Alarm calls also attract the attention of the predator, making it more likely that the individual making the call will be eaten. Why might natural selection cause a species evolve to make alarm calls? How might you test that hypothesis?
A very good hypothesis is that alarm calls have evolved by kin selection. If individuals that make alarm calls increase the survival of relatives, then a mutation for making alarm calls can gain enough indirect fitness through their survival to offset the increased mortality suffered by individuals that make the calls. A first step in testing this hypothesis would be to determine if individuals that hear alarm calls are more closely related to individuals making the calls than to random individuals in the population. A much more rigorous (and more difficult) test would be to estimate the fitness components and relatedness of altruists and recipients to determine if Hamilton's rule r B > C is satisfied. This approach would be similar to what was done in the analysis of cooperative male mating displays in turkeys.
If a population evolves under natural selection for a long period of time in a constant environment (without new mutations or migration), what will happen to the heritability (h2) of its traits? A) h2 ~ 0 B) h2 ~ 1 C) h2 ~ 0.5 D) h2 would drift randomly up and down over time
A) h2 ~ 0 It would stay the same because there is no migration, 0 genetic variation. Any changes are due to the environment ( no genetic variation + phenotypic measurement = flate line (0))
What are the implications of the neofunctionalization (Adaptation) model? What pattern do we expect for DN/DS? Do we expect to see signs of a selective sweep near the gene copies? A. The new copy should show DN/DS >> 1; the old should show DN/DS < 1. Selective sweep at the new copy only. B. The new and old copies should show DN/DS >> 1; Selective sweep at both copies C. The new copy should show DN/DS < 1; the old should show DN/DS >> 1. Selective sweep at the old copy only. D. The new copy should show DN/DS ~ 1; ; the old should show DN/DS < 1. Neither should show a selective sweep.
A. The new copy should show DN/DS >> 1; the old should show DN/DS < 1. Selective sweep at the new copy only. A new copy is beneficial so selective sweep occurs b/c the new copy is doing something different and it is doing it well. That is why DN/DS >> 1, the old copy is fixed and not spreading through.
parthogenesis
About 1 percent of plant species and 0.1 percent of animal species reproduce by making genetic clones of themselves- a sexual reproduction
altruistic interaction
Actor's fitness suffers but recipient benefits.
Neofunctionalization
Adaptation Model: One copy acquires a new function through mutation 1/3 examples of evolutionary models for fixation of gene duplication
life history
Age-specific probabilities of survival and reproduction that are characteristic of a species.
Antagonistic pleiotropy
Alleles increasing allocation to reproduction early in life that reduce function later in life. Both mechanisms explain how aging can arise through the declining relevance later life has for organismal fitness
evolutionary arms race
Also called escalation, may occur if the capture rate of the prey by the predator increases with the difference between the defensive trait of a prey species and a corresponding character in a predator. Then the characteristics of both species that affect their interaction evolve in one direction: for example, greater speed of gazelles and of pursuit predators such as cheetahs
reciprocal altruism
Altruistic behavior between non-kin can be maintained evolutionarily if individuals exchange acts of altruism
Yes, because the proportion of non-coding DNA shown a downward trend with effective population size.
Are the data consistent with Ne being a major cause of genomes having a lower proportion of non-coding DNA?
viruses and prokaryotes having similar effective population sizes, while eukaryotes have smaller
Assume the data shown are explained by differences in relative population size among viruses, prokaryotes, and eukaryotes. Describe how the effective population sizes of these three groups compare.
Support for the Red Queen hypothesis comes from the New Zealand mud snail (Potamopyrgus antipodarum), which has both sexual and asexual genotypes. Populations that are exposed to higher densities of parasites have higher frequencies of sexually reproducing individuals. Furthermore, because sexual females have lower infection rates, the fitness of sexual females is sometimes more than twice that of asexual females as shown in the figure
Attacks by parasites give an evolutionary advantage to sexual reproduction in the New Zealand mud snail (Potamopyrgus antipodarum), as predicted by the Red Queen hypothesis. The curves show the relative fitness of sexual females, using asexual females as the fitness reference, in three populations across 5 years. Sexual females usually have higher fitness than asexual females (points above the solid horizontal line). In some years, sexual females are more than twice as fit (points above the dashed horizontal line), showing that they have overcome the twofold cost of producing males. The higher fitness of sexual females results because they have lower rates of infection by parasites.
If a small population evolves for a long period of time in a constant environment (without new mutations or migration), what will happen to the heritability (h2) of its traits? A) h2 ~ 1 B) h2 ~ 0 C) h2 ~ 0.5 D) h2 would randomly drift up and down over time
B) h2 ~ 0 b/c no genetic variation + no drift
Why is it called the twofold cost of sex? A. Each individual has 2 offspring B. A pair of asexual individuals produce twice the number of offspring as a sexual pair C. Sexual reproduction always creates 2 offspring D. There are 4 asexual offspring for each sexually producing offspring
B. A pair of asexual individuals produce twice the number of offspring as a sexual pair
Why is it called the twofold cost of sex? A. Each individual has 2 offspring B. A pair of asexual individuals produce twice the number of offspring as a sexual pair C. Sexual reproduction always creates 2 offspring D. There are 4 asexual offspring for each sexually producing offspring
B. A pair of asexual individuals produce twice the number of offspring as a sexual pair
What trend of toxicity and resistance do we expect if they are coevolving? A. A negative correlation between garter snake resistance and newt toxicity B. A positive correlation between garter snake resistance and newt toxicity C. All ranges of garter snake resistance should be present at each level of newt toxicity D. Garter snake resistance should be higher than newt toxicity across all values
B. A positive correlation between garter snake resistance and newt toxicity
In our second simulation (i.e., of a mutualistic relationship), the number on each of the cards reflected the contribution of each species to the total, additive benefit both species experience. With this in mind, interacting species: A. Always received an equal benefit from the interaction B. Always received a benefit, but it was not always equal C. The interaction was altruistic and related to kin selection, and so any cost to one species ultimately would lead to its own genetic benefit
B. Always received a benefit, but it was not always equal
Suppose you visit two islands and record the number of closely related snake species, which prefer to prey upon a rodent species native to both islands. After collecting data, you notice that Island A has two species of snake, while Island B has 27 snake species. Based on this observation, which of the islands do you expect to have experienced coevolution and which of the islands do you expect to have experienced a diversification in prey preferences? A. Island A - coevolution; Island B - coevolution B. Island A - coevolution; Island B - diversification C. Island A - diversification; Island B - diversification D. Island A - diversification; Island B - coevolution
B. Island A - coevolution; Island B - diversification
In light of reproductive tradeoffs, would smaller or larger body size be beneficial for semelparous individuals? Why? Assume body size doesn't affect the total possible number of gametes individuals may produce, but that on average individuals produce many fewer gametes than possible. Semelparity: individuals reproduce only once and then die. A. Smaller, because it increases overall life span B. Smaller, because it allows more investment in fecundity C. Larger, because it increases overall life span D. Larger, because it allows more investment in fecundity
B. Smaller, because it allows more investment in fecundity
What are some examples of the benefits of parthenogenesis? What is a disadvantage?
Benefits: No sexually transmitted diseases, no need to find a mate. Disadvantage: no genetic mixing (no novelty through recombination)
spiteful interaction
Both individuals' fitness is harmed.
Which individual in generation 1 must have mated with individual C to produce the outcome we see in generation 2? How did sexual reproduction help the beneficial mutation become fixed? a) C must have mated with A. Recombination removed the two deleterious mutations in C. b) C must have mated with B. Recombination removed one deleterious mutation in C. c) C must have mated with D. Recombination added a deleterious mutation. d) C could have mated with A, B, or D, because recombination can eliminate C's deleterious mutations
C must have mated with A. Recombination removed the two deleterious mutations in C.
If there is selection for duplication of a gene to increase gene dosage, what DN/DS ratio would you predict in the new copy? A. DN/DS < 1 B. DN/DS ~ 1 C. DN/DS > 1
C. DN/DS > 1
For a weed adapted to a region with many forest fires, what life history traits would you predict? A. Fast growth, low somatic maintenance, low reproductive investment B. Slow growth, high somatic maintenance, low reproductive investment C. Fast growth, low somatic maintenance, high reproductive investment D. Slow growth, high somatic maintenance, high reproductive investment
C. Fast growth, low somatic maintenance, high reproductive investment
What is the most likely explanation for the very low fecundity of species such as whales, humans, and elephants? A. Low probability of offspring survival B. Iteroparous reproduction C. High investment in parental care D. High mobility E. All of the above
C. High investment in parental care
What evolutionary processes besides natural selection on whole organisms could make genome size increase over time? Pick all answers that apply: A. Small changes to the genome's size could accumulate by drift over time. B. Sexual selection for bigger males could cause larger genomes. C. Like cancerous cells in a body, DNA segments can reproduce and dominate a cell's genome. D. Gene flow between populations could cause a higher mutation rate.
C. Like cancerous cells in a body, DNA segments can reproduce and dominate a cell's genome.
For a science project, you breed a large colony of mice for long fur. Eventually, you succeed in breeding a very wooly mouse. Excited to dissect the genetic basis of your wooly mice, you sequence the exomes of the wildtype strain and the wooly strain only to find no difference. Why do you think that is? A. Sequencing is inherently error-prone so you probably just missed the one or two mutations responsible B. The wooly phenotype is not due to a genetic change C. The difference probably lies in a regulatory region of the genome D. You should have used primers for a sheep exome, not a mouse exome
C. The difference probably lies in a regulatory region of the genome
Implications of DDC Model (subfunctionalization): What pattern do we expect for DN/DS? Do we expect to see signs of a selective sweep near the gene copies? A. We expect DN/DS > 1 and evidence of selective sweeps near both copies B.We expect DN/DS ~ 1 and no evidence of selective sweeps near both copies C. We expect DN/DS between 0 and 1, and no evidence of a selective sweep near either copy D. We expect DN/DS between 0 and 1, and evidence of a selective sweep near copy C2
C. We expect DN/DS between 0 and 1, and no evidence of a selective sweep near either copy
TTT ACT AAT AGT TTC CCT AAC GAT 2/2 = 1
Calculate the DN/DS
What are the implications of the dosage effect model? What pattern do we expect for DN/DS? Do we expect to see signs of a selective sweep near the gene copies? Model: • Gene duplication creates twice as much gene product • Positive selection for more protein drives gene duplication to fixation • No mutations occur in either gene cop
Coding is unchanging, will see purifying selection, DN/DS = 0. There would be signs of selective sweep b/v duplication is sweeping through and would expect reduced variation near each copy
B) Delta(z) = 0; h2 = 0; and S = -0.5 mm S = survivors-parentals (8.3-8.8 = -0.5) h2 = 0 change Z = change in parent offspring (8 - 8 = 0)
Considera hypothetical scenario where you observed the Darwin's finch, Geospiza difficilis, before and after a drought. Now imagine that you looked at the offspring of the survivors. Using this data, what are Δz, h2, and S? A) Delta(z) = 0.5; h2 = 1; and S = -0.5 mm B) Delta(z) = 0; h2 = 0; and S = -0.5 mm C) Delta(z) = 0.5; h2 = 0; and S = -0.5 mm D) Delta(z) = 0; h2 = 0; and S = 0.5 mm E) Delta(z) = 0; h2 = 0.5; and S = -0.5 mm
If individuals can reproduce asexually or sexually, but they always have two offspring in either case, how fast will a pure asexual versus a pure sexual population grow? A. Both stay the same size B. Both grow linearly C. Asexual grows linearly; sexual stays the same D. Asexual grows exponentially; sexual stays the same
D. Asexual grows exponentially; sexual stays the same
If individuals can reproduce asexually or sexually, but they always have two offspring in either case, how fast will a pure asexual versus a pure sexual population grow? A. Both stay the same size B. Both grow linearly C. Asexual grows linearly; sexual stays the same D. Asexual grows exponentially; sexual stays the same
D. Asexual grows exponentially; sexual stays the same
Two bird species colonize an island and initially eat the same species of beetle. Which of the following outcomes CANNOT occur over the course of evolution? A. One of the species goes extinct B. One of the species shifts to consume another species of beetle C. The two species continually develop adaptations reflective of reciprocal genetic changes through time to out-compete the other D. Both species continue consuming the same food source at the same rate, indefinitely
D. Both species continue consuming the same food source at the same rate, indefinitely
If every mammalian cell has the same small chance of becoming cancerous, what prediction should follow as a result: A. Lower cancer rates in species with larger bodies and shorter lives B. Higher cancer rates in species with larger bodies and shorter lives C. Lower cancer rates in species with larger bodies and lifespans D. Higher cancer rates in species with larger bodies and lifespans
D. Higher cancer rates in species with larger bodies and lifespans
In which situation would you expect the interacting parties not to cooperate? A. The individuals are closely related B. The individuals have a history of repeated social interactions C. An individual that provides assistance in the present will in turn be assisted in the future D. Individuals are unlikely to encounter each other again in the future E. Individuals are part of a social group in which noncooperating individuals are punished
D. Individuals are unlikely to encounter each other again in the future
The correct interpretation of DN/DS ratios is..
DN/DS<<1 = negative selection DN/DS ~ 1 = neutral DN/DS >> 1 = positive selection increase in amino acid changes = positive, being added decrease in amino acid changes = negative, being eliminated
kin selection theory expanded
Direct fitness: Measured as the number of offspring an individual has that survives to a reproductive age Indirect fitness: Helping your relatives (your kin). Copies of your alleles are reproduced in your relatives. Your relatives have more alleles in common with you than with an unrelated individual Inclusive fitness = direct fitness + indirect fitness. The more alleles you have in common with another individual, the more interest you have in helping them. This relationship is quantified by Hamilton's Rule
B. No, all the genotypes are responding to the environment in the same way
Does this diagram depict a gene x environment interaction? A. Yes B. No, all the genotypes are responding to the environment in the same way C. There isn't enough information to tell D. Reaction norms don't have anything to do with genes and environment
increased copy number
Dosage Effect Model: Both copies retain their original function 1/3 examples of evolutionary models for fixation of gene duplication
subfunctionalization
Duplication-Degeneration Complementation (DDC) Model: The duplicate copies lose one of the gene's original functions 1/3 examples of evolutionary models for fixation of gene duplication
Populations of some species of fish, insects, and crustaceans consist of both sexually and obligately asexually reproducing individuals.What factors might maintain both reproductive modes?
Factors that might maintain a given mode of reproduction might include access or availability of mates, disease, or parasites. For example, if diseases and parasites have a major effect on the population, the Red Queen hypothesis suggests that sexual reproduction would be favored.
T/F In co-evolution, reciprocal genetic change through natural selection implies there's always one species who wins and one who loses
False. There is no fixed winner in natural selection. It's not always a predator/prey interaction. Both species could potentially lose in co-evolution and there's a range of possible interactions in co-evolution
Design a hypothetical experiment to determine whether greater virulence is advantageous in a horizontally transmitted parasite or in a vertically transmitted parasite.
Greater virulence will be advantageous to a parasite despite its mode of transmission if increased virulence also increases fitness. Generally, greater virulence will increase the reproductive rate of a horizontally transmitted parasite but at the cost of increased risk of mortality for the host (and thus the parasite). The key to a successful experiment to determine advantage is to measure whether reproductive rate or risk of mortality increases faster.
D. We expect to both species benefit, so a positive correlation for both figures
Here is a similar example to the moth and flower, this time with fly and iris species. What relationships in the figures shown below would be consistent with mutualistic co-evolution? A. We expect only flies to benefit, so nectar consumed should correlate positively with proboscis length while pollen deposition should correlate negatively with tube length B. We expect only flowers to benefit, so nectar consumed should correlate negatively with proboscis length while pollen deposition should correlate positively with tube length C. We expect both species to benefit, so a negative correlation in both figures D. We expect to both species benefit, so a positive correlation for both figures
b. Both genes turn on eye development, but different genes are regulated by them in different species.
Human eyes have a very different morphology from that of fly eyes. If Pax6 sequence and function is highly conserved, how can one explain morphological divergence in eyes and their ectopic expression in these flies? a. Pax6 and eyeless genes arose independently, but have similar function. b. Both genes turn on eye development, but different genes are regulated by them in different species. c. Pax6 does not suppress eye development as well as eyeless. d. Pax6 and eyeless must not be part of the developmental pathway.
Relatedness in haploid species
If a worker (female) carries a rare allele, the only way her brother can also carry it is if she inherited the allele from their mother (probability = 1/2) and if the mother passed the allele to her son (probability = 1/2). The alleles in the brother are therefore related to those in the worker by r = 1/2 × 1/2 = 0.25. However, there are two ways that a new queen (the worker's sister) might also carry the worker's allele. The worker might have inherited the allele from their mother (with probability = 1/2), and if so the mother might have passed it to the sister (with probability = 1/2). Alternatively, the worker might have inherited the allele from their father (with probability 1/2). If so, then her sister is certain to carry it also, because males are haploid and always transmit all of their genes to all of their offspring.
Half of the individuals are males that do not give birth, so the population size is constant. An asexual female then appears, for example by mutation, and she also has two offspring. But since all of her offspring are asexual females, the number of asexual individuals doubles in each generation. In short, a mutation for asexual reproduction enjoys a 100 percent fitness advantage over an allele for sexual reproduction, and it will spread to fixation in only a handful of generations as shown in the below figure B.
If all else is equal, a mutation in a sexual population that causes females to reproduce asexually will spread to fixation in just a few generations. The fact that asexuality is so rare shows that there must be strong advantages to sexual reproduction that compensate for the twofold cost of producing males.
Corn height averages about 5' in height. However, to test if corn height is determined by the environment or by genetics from the parents, 7' tall corn plants are selected and bred. If the height of the offspring of the 7' tall parents was 5', what would the heritability variance value be? If the height of the corn plants was 7', what would heritability variance value be?
If heritability is purely environmental, the variance would be 0. If heritability is based on genetics, the variance would be 1.
The effects of the parasite will create an environmental cue for C. elegans to reproduce sexually more often in both populations compared to the one without the parasite. However, coevolution between parasite (S. marcescens) and host (C. elegans) should create an ongoing struggle to evolve faster on each side (the Red Queen Hypothesis). We would predict that the outcrossing rate will therefore stay elevated after its initial increase. With an unchanging parasite, however, there will be stabilizing selection on C. elegans rather than coevolution. We therefore expect outcrossing rates will peak and then decline as C. elegans adapts to resist S. marcescens.
If the Red Queen Hypothesis is right for this system, how should the outcrossing rate differ over time for the experiments with an unchanging parasite versus a coevolving parasite?
Example of selfish interaction: This species has an odd life history. When food is scarce, individual cells aggregate to form a "slug." The slug wanders a bit, then transforms into something like a very small mushroom with a spherical cap on top of a stalk. Cells in the cap form spores that disperse. The cells in the stalk die without reproducing, sacrificing themselves for the good of the cells that make the spores. Some cells carry a cheater mutation that makes spores but that avoids contributing to the stalk. In laboratory culture, the frequency of this mutation increases over the course of several life cycles
In the slime mold Dictyostelium discoideum, cells with a mutation at the chtA locus are cheaters that behave selfishly. In a mixture of wild-type cells (in yellow) and cells with thechtAmutation (blue), the mutant cells become concentrated in the cap and so are more likely to form the reproductive spores. Over the course of 11 growth and development cycles, the frequency of the selfish mutant increased in laboratory culture
C. I can't tell without seeing more genotype reaction norms
Is this diagram an example of gene-environment interaction? A. Yes B. No C. I can't tell without seeing more genotype reaction norms D. It depends on which environment the genotype is in
A friend comes to you for advice, knowing that you are studying evolution. He is a frog breeding enthusiast. He wants to increase the rate at which he can breed new phenotypes of frogs. He knows that the amount of variation in the population affects the rate of evolution, so he has devised this clever plan. He has set up a large grid of tanks for raising his tadpoles, each tank with a different environment (e.g., temperature, light exposure, algae content, etc.). He knows that these different environments will cause different phenotypes to develop in the different tanks, thus increasing the phenotypic variation in the population. He can then select from that variation to breed for any desired trait. What do you think of his plans and why?
It's a good experiment to see what types of phenotypes present themselves due to the various environmental factors. He is attempting to manipulate phenotype plasticity but expects this to affect the genotype of the frogs. Unfortunately, the genotype will not be changed. All of his tadpoles will pass on the same genotypes to their offspring despite the fact that their environments made them look different.
Female parasitoid wasps search for insect hosts in which to lay eggs, and they can often discriminate among individual hosts that are more or less suitable for their offspring. Behavioral ecologists have asked whether or not the wasps' willingness to lay eggs in less suitable hosts varies with the female's age. On the basis of life history theory, what pattern of change would you predict? Does life history theory make any other predictions about animal behavior?
Life history theory would predict that older females should be less choosy about hosts in which to lay their eggs. When time to reproduce is running out, females should attempt to have as many offspring as possible to increase the chances of some surviving, rather than waiting for a suitable host and risking death before reproducing. Optimality theory is an important approach for understanding evolution of life history adaptations and is used extensively in the study of animal behavior.
Why is linkage disequilibrium important?
Linkage disequilibrium is important because it affects how genes evolve; selection on one locus can cause a second locus to evolve if the two loci are in linkage disequilibrium. A second reason that linkage disequilibrium is important is that it allows us to find genes that affect traits of interest. This idea is used to study the genetic basis of traits as diverse as the size of a tomato and adaptation to high elevation in humans
What is the common difference between sexes in all three cases?
Males contribute small gametes while females contribute large gametes
Mutation accumulation
Mutations that compromise biological functions later in life exert a lesser effect on fitness than those acting earlier. Both mechanisms explain how aging can arise through the declining relevance later life has for organismal fitness
What is the C-value paradox?
Number of base pairs in eukaryote genomes does not correlate well with organismal complexity
What is the G-value paradox?
Number of genes in eukaryote genomes does not correlate well with organismal complexity
Examples of Red Queen Hypothesis: C elegans
Outcrossing Rate in C. elegans- Some species are capable of reproducing sexually and asexually depending on environmental signals (cues) -C elegans has males and hermaphrodites; the hermaphrodites are able to self fertilize according to environment -C elegans has a parasite, S. marcescens
twofold cost of sex
Parthenogenesis has evolutionary advantages that should make it more common than sexual reproduction. By far the most important of these is the twofold cost of males: if all else is equal, the production of males in a sexual population reduces its reproductive potential by a factor of two. In the figure: The biggest evolutionary disadvantage of sexual reproduction is the twofold cost of males. (A) Each female produces two offspring. The sexual females are exactly replacing themselves, and their numbers are stable. Asexual females produce only daughters, and so their numbers double in each generation.
There are many traits for which it seems natural selection should favor an increase every generation, such as survival from birth to reproduction. In most cases, when we look for such increases in natural populations we do not see the predicted change. Make a list of all the reasons we might not see a response to directional selection on such a trait. Include reasons suggested by the material in this chapter, as well as any other reasons you can think of.
Potential reasons include a lack of any form of genetic variation, a lack of additive genetic variation, conflicting selection on other traits that are genetically correlated with the trait of interest, environmental change from generation to generation such that the alleles that increased the trait in the last generation do not necessarily increase it in this generation, and a continuing deterioration in the environment that causes evolutionary increases to be balanced by environmentally driven decreases.
What is sexually antagonistic selection?
Sexual dimorphism evolves when selection favors the expression of a trait to be different in males and females.
Co-evolution
Reciprocal genetic change in interacting species, owing to natural selection imposed by each on the other • Reciprocal means each species causes changing allele frequencies in the other • Interaction requires populations to exist in the same area and time
selective interference
Reduction in the spread of an advantageous allele that results from selection acting on other loci.
Anisogamy
Refers to a difference in gamete size in males and females. Eggs large and costly, sperm small and cheap. (dimorphism in gamete size)
Given the relatedness between cancer cells from the same clone, cancers cells from different clones and normal cells, what are your predictions about the evolution of cell level cooperation within cancers and between cancers and normal cells? Why?
Relatedness between two cells in body is 100%. The new cancer cell and normal cell relatedness is 0 %but as the cancer grows, all the cells around inherit that allele within that locus. Therefore, the evolution of cooperation within cancer cells will increase. The cancers located close to each other will also being to cooperate, and will eventually invade normal cells.
Need-based transfers
Resource sharing based on the need of the recipient
K-selection
Selection for life history traits that are sensitive to population density; also called density-dependent selection. • Dominant where the population is near/at carrying capacity • Selection for genotypes with higher carrying capacities (K) • Ensuring offspring survive competition to reproduce leads to highest fitness
r-selection
Selection for life history traits that maximize reproductive success in uncrowded environments; also called density-independent selection. • Dominant where the population is at low density, i.e. far from carrying capacity • Selection for genotypes with high per capita growth rates (r) • Having more offspring faster leads to highest fitness
an example of recombination rates
Selective interference in Drosophila melanogaster decreases the rate of adaptive evolution in regions of the genome that have low recombination rates. The x-axis shows the recombination rate (in centimorgans [cM] per megabase [Mb] of DNA); regions of the genome with high recombination are to the right. The y-axis shows a measure of the rate of adaptive amino acid changes in proteins. Genomic regions with higher recombination rates have higher rates of adaptive evolution
A.) C must have mated with A. Recombination removed the two deleterious mutations in C.
Sexual reproduction only in this case. Red mutations are deleterious. Yellow mutations are beneficial Which individual in generation 1 must have mated with individual C to produce the outcome we see in generation 2? How did sexual reproduction help the beneficial mutation become fixed? A.) C must have mated with A. Recombination removed the two deleterious mutations in C. B.) C must have mated with B. Recombination removed one deleterious mutation in C. C.) C must have mated with D. Recombination added a deleterious mutation. D.) C could have mated with A, B, or D, because recombination can eliminate C's deleterious mutations
Populations of some species of fish, insects, and crustaceans consist of both sexually and obligately asexually reproducing individuals. How might studies of these species shed light on the factors that maintain sexual reproduction?
Sexual selection is thought to be one way by which sexual reproduction is maintained, because only fit males are able to mate. In an environment free from enemies, asexual reproduction would be favored, but are unlikely to persist over evolutionary time, because when the environment changes they will have much less ability to adapt (owing to a lack of novel genetic variation that would be provided by segregation and recombination in a sexual population).
How did sexual dimorphism evolve?
Sexually antagonistic selection
How did sexual dimorphism evolve?
Sexually antagonistic selection: Sexual dimorphism evolves when selection favors the expression of a trait to be different in males and females.
On average, there is less recombination between pairs of DNA bases on a chromosome when they are closer to each other than when pairs are farther apart. For that reason, D tends to be higher between pairs that are closer as shown in the figure
Shown is a region of 500 thousand base pairs (kb) of a chromosome sampled from 89 humans in eastern Asia. The x-axis and y-axis are positions along the chromosome. Three sites on the chromosome are labeled. Sites A and B are relatively close (50 kb), and they have high linkage disequilibrium (indicated by red). Sites B and C are farther apart (250 kb), and they have low linkage disequilibrium (indicated by white).
relatedness in diploid species
Sister-sister coefficient: r=0.5 Sister-brother coefficient: r=0.5
Which life history features would make natural selection more likely to favor alleles investing in DNA damage sensitivity and repair? A. Slow reproduction B. Fast reproduction C. High survival D. Low survival E. Many offspring F. Few offspring G. High maintenance of body H. Low maintenance of body
Slow reproduction, high survival, few offspring, high maintenance of body
Explain what the ratio DN/DS tells us and why we divide DN by DS
The DN/DS ratio tells us whether there is evidence for selection acting on the coding region of the gene. A value close to zero indicates purifying selection, close to one indicates little/no selection, and much larger than one indicates positive selection. Dividing the number of non-synonymous changes by the number of synonymous changes allows us to compare mutations likely to affect the protein's function (non-synonymous changes) against the background rate of mutations with minimal or no effect (synonymous changes). DS therefore allows us to calibrate our expectations for whether DN is higher, lower, or the same as what we would expect if selection were absent.
Genome size
The amount of DNA contained in one copy of a genome & describes all of the genetic material contained in a living organism's cells
What is effective population size?
The average number of individuals in a population that contribute genes equally to the next generation. Usually smaller than the actual population size
r/K selection theory
The effect of the environment on the timing and number/size of offspring. r and K selection treats distance from carrying capacity as the dominant factor for life history evolution
At many sites in the genome, an Alu element is present in humans but absent in chimpanzees, while at many other sites an Alu element is present in chimpanzees but absent in humans. What are two hypotheses that could explain this situation? For any particular site, how could the hypotheses be distinguished?
The first hypothesis is that an Alu element was present at the site in the common ancestor of humans and chimpanzees, and then was lost in one of the two lineages. The second hypothesis is that it was inserted into the site in one of the two lineages since they diverged. To distinguish the two possibilities, the same site in a gorilla genome could be examined. If the Alu sequence is present in the gorilla, that implies it was also present in the ancestor of chimpanzees and humans. This supports the first hypothesis. If the Alu sequence is absent at that site in the gorilla, most likely it was also absent in the common ancestor of humans and chimpanzees, and was inserted at that site in one of the lineages. This supports the second hypothesis.
gene duplication
The generation of extra copies of a gene in a genome over evolutionary time. A mechanism by which genomes can acquire new functions.
The human sex chromosomes give a graphic example of the evolutionary consequences of giving up recombination. The Y chromosome originated from a recombining X chromosome some 180 million years ago, and then ceased to recombine with the X[5]. From that point onward, the Y chromosome has evolved asexually, like the mitochondria that are passed through the female lineage. Meanwhile, the X chromosome continues to recombine in females. As various forms of selective interference caused the Y chromosome to degenerate, it lost almost all of the 2000 or so genes and more than 60 percent of the DNA carried on the X[6]. As a result, we now see dramatic differences between the X and Y chromosomes as shown in the figure
The human sex chromosomes, as seen in a scanning electron micrograph. The Y chromosome (at left) does not recombine. Selective interference caused it to degenerate from an ancestor that was much like the X chromosome (at right).
Recombination causes linkage disequilibrium to decrease. The value of D declines toward 0 rapidly when the recombination rate is large (r = 0.5), and slowly when it is small (r = 0.01).
The most important role that recombination plays in evolution is through its effects on D. If Mendelian inheritance is the only factor at work, the value of D in the next generation is decreased by a proportion r from its value in the current generation. Thus recombination causes the population to evolve toward linkage equilibrium with D = 0. It does so quickly if r is large (near 1/2) and slowly if r is small (near 0). The evolution of D with three different values of r is shown in the figure below.
The Two-Fold Cost of Sex Assume females in a population can switch by mutation between two systems of reproduction • Asexual reproduction to make two females • Sexual reproduction to make one male and one female
The production of males then reduces female reproductive potential by a half
dN/dS ratio
The ratio of the number of nonsynonymous substitutions per nonsynonymous site (dN) and the number of synonymous substitutions per synonymous site (dS). Values of this ratio smaller than one are consistent with purifying selection, while values greater than one suggest the action of positive selection. A high proportion of amino acid changes indicates selection
horizontal gene transfer
The transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms.
The human genome contains more than a million copies of the Alu transposable element. Comparative genomics reveals that the Alu element is found only in the clade of mammals that includes primates, tree shrews, rodents, and rabbits. a. What does the observation that the Alu transposon is limited to this clade reveal about its origin and method of spread among species?
This observation shows that the Alu element originated in the common ancestor of that clade and was then passed vertically to descendant species. There is no evidence that Alu can be transmitted horizontally from one species to another.
Explaining linkage disequilibrium (D)
Three populations of eight gametes that have the same allele frequencies (pA = pB = 1/2) but have different values of linkage disequilibrium. Linkage disequilibrium is defined the same way regardless of whether the two loci are on the same chromosome or on different chromosomes. (A) When the disequilibrium, D, between alleles A2 and B2 is positive, those alleles are found together more often than if they were associated at random. When D is at its maximum possible value (D = 1/4), a gamete that carries allele A2 always carries allele B2. (B) When disequilibrium is at its smallest possible value (D = -1/4), a gamete that carries allele A2 always carries allele B1. (C) When a population is at linkage equilibrium (D = 0), there is no association between alleles at the two loci. If a sperm carries allele A2, the chance that it also carries allele B2 is simply the frequency of B2 in the population.
T/F The more an altruist increases their relatives' fitness, the more the altruistic gene will increase in frequency in the population.
True As long as their altruistic behavior is directed at relatives (e.g. they are usually surrounded by relatives) the altruistic gene will spread.
Specific coevolution:
Two species evolve in response to each other (e.g. "evolutionary arms race").
r = .5*.5*.5 = .125
What is the actors relatedness to the cousin?
1/2*1/2 + 1/2*1/2 = 1/2 = 0.5 r = .5
What is the actors relatedness to the sister
0.125
What is the ratio of total sexual individuals to total asexual individuals in generation 4? Give your answer as a decimal
C. Crossbill predation creates fitness differences among pines based on their cone traits
What type of evolutionary relationship does the evidence support between crossbills and pines? A. Pines have undergone genetic change due to selection on cone traits B. Crossbills have undergone genetic change due to selection on cone traits C. Crossbill predation creates fitness differences among pines based on their cone traits D. Pines create fitness differences among crossbills based on cone traits
B. Crossbills have undergone genetic change due to selection on bill depth
What type of evolutionary relationship does the evidence support between crossbills and pines? A. Pines have undergone genetic change due to selection on cone traits B. Crossbills have undergone genetic change due to selection on bill depth C. Crossbill predation creates fitness differences among pines based on their cone traits D. Pines create fitness differences among crossbills based on cone traits
C. Squirrel predation creates fitness differences among pines based on their cone traits
What type of evolutionary relationship does the evidence support between red squirrels and pines? (Recall: Longer cones with fewer seeds are less likely to be eaten) A. Pines have undergone genetic change due to selection on cone traits B. Squirrels have undergone genetic change due to selection on cone traits C. Squirrel predation creates fitness differences among pines based on their cone traits D. Pines create fitness differences among squirrels based on cone traits
linkage disequilibrium
When a pair of alleles from two loci are inherited together in the same gamete more/less often than random chance would expect- linkage equilibrium takes more than one generation to reach- depends on the rate of recombination between the loci. Less recombination (smaller r) means the genes at a pair of loci mix more slowly, so linkage equilibrium between them takes longer to reach
The data provide evidence for genetic change in crossbills due to selection pressures imposed by eating pine cones. Support for this comes from comparing the optimal bill depth in the rocky mountains, where squirrels are present, against the south hills, where squirrels are absent. Specifically, the optimal beak depth is smaller in the rocky mountains where squirrels are the dominant predators. As in the previous diagram, this shows selection will act on genetic variation in beak depth to move a population in South Hills toward the local fitness peak at ~10mm.
When both are present, squirrels are the dominant predator, affecting crossbill fitness indirectly. The absence of squirrels in South Hills lets us see if they affect the optimal beak depth of crossbills What type of evolutionary relationship do the data support between crossbills and pines? Explain your reasoning.
conflict interaction
When fitness interests of both individuals are different.
When would you predict sex-role reversal so that males are the choosier sex and females battle for males? (according to the model for evolving dimorphism from anisogamy)
When male investment speeds up female generation time. Also, When many males die from male-male competition, heavily biasing the sex ratio toward females
cooperation interaction
When one individual's behavior benefits the other's fitness. Important: In sociobiology and behavioral ecology, cooperation does not mean working together towards a common goal. As evolutionary biologists we are analyzing fitness effects of behaviors.
A. When male investment speeds up female generation time B. When many males die from male to male competition Correct ans: D
When would you predict sex-role reversal so that males are the choosier sex and females battle for males? A. When male investment speeds up female generation time B. When many males die from male-male competition, heavily biasing the sex ratio toward females C. A new mutation arises lowering the cost of producing sperm D. A and B E. All of the above
Mixed Evolutionarily Stable Strategy (ESS)
Where two strategies permanently coexist. For a given set of payoffs, there will be one set of frequencies where the mix is stable
Event 4- because it changes function, not the # of copies or a loss.
Which duplication event in the figure led to change in the gene's evolutionary function?
Example B look for a pattern where they line up and should go from top to bottom
Which of these options shows evidence of selective sweep?
A. Minimum genome size
Which option shows a clear trend from prokaryotes to birds/mammals/reptiles? A. Minimum genome size B. Average genome size C. Maximum genome size D. None of the above
A. Specific coevolution because they have evolved together, 1:1 pairing- branches match
Which type of co-evolution is this tree most consistent with? A. Specific coevolution B. Diffuse coevolution C. Escape-and-radiate coevolution D. None of the above
Biggest predictor of sharing is not debt but whether the recipient is hungry. The recipient who is hungry one day may be the actor who feeds another the next day.
Why do need-based transfers out-perform debt-based systems
B. A is 13 and B is 10
You are studying the life tables of two species: A and B. They produce the same number of offspring throughout their lives, but the probability of females' surviving to a certain age differs. Calculate their R values to determine which species has a higher reproductive success, A or B. A. A is 10 and B is 14.5 B. A is 13 and B is 10 C. A is 11 and B is 9 D. A is 8 and B is 6
Retrotransposition
a form of transposition in which the element is transcribed into RNA. The RNA is then used as a template via reverse transcriptase to synthesize a DNA molecule that is integrated into a new region of the genome via integrase
hitchhiking occurs when:
a mutation genetically linked to that beneficial mutation also becomes fixed (an example of indirect selection)
diffuse coevolution
a network of species undergoes reciprocal evolutionary change through natural selection also called guild evolution
selective sweep
a process in which one allele increases in a population due to positive selection
Pure Evolutionarily Stable Strategy (ESS)
a single behavioral strategy that is resistant to invasion and most likely to be maintained by natural selection
scenesence
a way to describe the variation in lifespans- physiological changes that lower an organism's survival and reproduction with age.
Which of the following does not represent a life history trait? a. Defenses against predation b. Age-specific fecundity c. Age at sexual maturity d. Adult body size
a. Defenses against predation
Imagine a scenario in which several lakes have been colonized by marine-origin sticklebacks. In each lake, body armor disappears over time. Which change most likely caused this? a. Independent, unique mutations occurred in each population that rendered enhancers in the armor pathway useless, which were then favored by natural selection. b. Each population had the exact same mutation in a protein coding gene that produces the armor, which increased in frequency by natural selection. c. Novel trans-regulatory elements functioned to build new, armorless morphologies that increased in frequency because of gene flow from oceanic populations. d. Lack of armor reduces fitness, so only genetic drift could cause the armorless condition to increase in frequency.
a. Independent, unique mutations occurred in each population that rendered enhancers in the armor pathway useless, which were then favored by natural selection.
ndividual amoebae of the slime mold Dictyostelium discoideum aggregate to form a spore-producing fruiting body. Cheaters make spores, but do not contribute to the stalk. Since many more spores with cheating genotypes are dispersed, they have higher fitness. Why does directional selection not lead to fixation of the cheater genotype? a. This is actually a case of frequency-dependent selection. With too many cheaters in a population, the fruiting body's stalk is not built well, and all individuals have lower fitness. b. Noncheating genotypes are maintained for the harmony and balance of nature. c. Individual amoebae compete against groups of multicellular predators; the noncheating genotype is favored during this competition. d. Individual amoebae form "slugs" only with other amoebae that have the same genotypes. e. Reproductive success is independent of whether an organism exists as a single cell or as part of a multicellular "slug."
a. This is actually a case of frequency-dependent selection. With too many cheaters in a population, the fruiting body's stalk is not built well, and all individuals have lower fitness.
selfish interactions
actor's fitness increases, recipient's fitness is harmed.
Why might having more copies of a gene be adaptive?
benefit to redundancy, allows for more regulation to turn genes on & off in favorable ways, more of a protein (ex: amylase, an enzyme that allows us to digest starch. More copies of AMY1 gene allows for more amylase proteins to be made)
Which is an example of aposematism? a. The snowshoe hare's coat color helps it effectively hide from predators. b. Brightly colored wings on a butterfly warns predators that it is toxic. c. Eyespots on a moth's wings deceive a predator into believing it is being watched. d. Cleaner wrasse sit still in a conspicuous location to advertise that they will eat parasites off of the gills of larger fish. e. The dominance of a male gorilla is indicated by silver-gray hair on its back.
b. Brightly colored wings on a butterfly warns predators that it is toxic.
What is the best explanation for the observation that eukaryotes that seem superficially simple can have much larger genomes (in terms of mass or number of base pairs) than organisms that have complex anatomy, structure, or behavior? a. Alternative splicing and overlapping genes are rampant among eukaryotes. b. Some organisms have a tremendous amount of noncoding DNA, like repetitive sequences. c. Simpler organisms require more chemical defenses against enemies. d. Animals with simple body plans are adapted for rapid DNA replication.
b. Some organisms have a tremendous amount of noncoding DNA, like repetitive sequences.
Because increased fecundity means increased fitness, we might expect to observe the evolution of ever-increasing fecundity, but this is not the case. Which reason for lower-than-expected fecundity is plausible? a. While beneficial to the population or species, selection for increased fecundity is harmful to the individual. b. There are allocation trade-offs between fecundity and other traits. c. All of the above are plausible reasons. d. Increased fecundity leads to overpopulation and mass starvation, due to increases in individual fitness.
b. There are allocation trade-offs between fecundity and other traits.
Which mechanism for the appearance of a new gene in a species' genome could also explain different phylogenetic tree topologies when using different genes? a. Retrotransposition b. Neofunctionalization after gene duplication c. Horizontal gene transfer d. Exon shuffling
c. Horizontal gene transfer
Plants that evolved resistance to herbivores were able to diversify rapidly. Some butterflies overcame these defenses and also diversified rapidly. This is an example of _________. a. specific coevolution b. diffuse coevolution c. escape-and-radiate coevolution d. guild evolution e. simple coevolution
c. escape-and-radiate coevolution
uppose five boats are adrift at sea, each one containing a number of your relatives, and you have the power to save one boat from a dire fate. According to kin selection theory, it would be in the best interest of your genome to save a boat that contains ______. a. two of your brothers b. both of your parents c. one sister, one half-brother, and three cousins d. four half-siblings
c. one sister, one half-brother, and three cousins
Evolution of cooperation in an experiment with the bacterium Pseudomonas aeruginosa. The cooperator genotype excretes siderophores, which are used by neighboring bacteria to take up iron from the medium. The cheater genotype does not excrete siderophores, but benefits from the siderophores made by others. Bacteria evolved in cultures that were maintained with either low relatedness (low r) or high relatedness (high r), and with either weak competition (weak comp) or strong competition (strong comp) between relatives. The cooperator genotype increased in frequency when there was high relatedness and weak competition.
cooperation in bacteria
genetic recombination
creates novel combinations of variation
Which of these describes antagonistic pleiotropy? a. Mating only once in life, then dying b. Steep reduction in fertility and fecundity later in life c. Intrinsic changes that lower survival and reproduction with age d. Genes that increase reproduction may decrease survival later in life
d. Genes that increase reproduction may decrease survival later in life
Which event will not alter an organism's karyotype? a. Allopolyploidy b. Chromosome fission c. Chromosome fusion d. Sequence inversion
d. Sequence inversion
You are in an area famous for the presence for cuckoo birds, and you notice a mother bird kicking eggs out of its nest. What is the most likely explanation? a. The bird is sacrificing the eggs to distract the cuckoo birds from its other eggs. b. The mother does not want its offspring to be stolen by the cuckoo birds. c. The bird wants to have fewer offspring to reduce the effort involved with rearing them. d. The bird has recognized an attempt at brood parasitism and is removing the threat. e. Too many eggs attract cuckoo birds and the mother is reducing the threat.
d. The bird has recognized an attempt at brood parasitism and is removing the threat.
Which observation is inconsistent with Haeckel's idea that "ontogeny recapitulates phylogeny"? a. The backbone—the common structure among all vertebrates such as fish, reptiles, and mammals—appears as one of the earliest structures in all vertebrate embryos. b. Snakes and legless lizards develop "leg buds" as embryos, only to have them reabsorbed prior to hatching. c. All tetrapod embryos display pharyngeal clefts, a notochord, segmentation, and paddlelike limb buds. d. The pharyngeal clefts and branchial arches of embryonic mammals and reptiles never acquire the form seen in adult fish.
d. The pharyngeal clefts and branchial arches of embryonic mammals and reptiles never acquire the form seen in adult fish.
The evidence for selective sweep
decays over time
Symbiosis
describes an intimate association between two species that is located along a continuum from mutualism to parasitism/predation. Symbiosis of any type may cause co-evolution Diagram shows possible symbiotic interactions
If the two loci are on different chromosomes, when an individual makes a gamete there is a chance of _____ that one of the chromosomes it carries will be from the mother and the other from the father. This would be the _____ possible value for the recombination rate
f the two loci are on different chromosomes, when an individual makes a gamete there is a chance of 1/2 that one of the chromosomes it carries will be from the mother and the other from the father. Here r = 1/2, which is the maximum possible value for the recombination rate
How did eusociality originate?
facilitated by kin selection; These hymenopterans were predisposed to sociality because they already had the habit of caring for offspring and because the nest provided a safe place—a fortress—for grown offspring to stay and to interact with their mother and younger sibling
mutualistic interactions
fitness of both individuals is increased through interaction
Pseudogenes
former genes that have accumulated mutations and are nonfunctional
Breeder's Equation: If I tell you the heritability of a trait and the difference between the mean of the trait in the parental population versus the mean of those organisms that survive and reproduce, can you predict the change in that trait in the next generation? For example, if a population has a mean height of 180cm but the ones who survive and manage to reproduce have a mean height of 190, and you know that the heritability of height is 0.8, what should be the mean height of the next generation (in cm)?
h^2 = .8 = 80% heritability S = 190 - 180 = 10 change z = h^2s = .8(10) = 8 180 + 8 = 188 The mean height of the next generation will be 188cm
Müllerian mimicry
in which two or more unpalatable species are co-mimics (or co-models) and jointly reinforce aversion learning by predators The models vary in abundance between localities, and the mimic that matches the common model survives best. Left: In one locality, the model species H. eleuchia is most common. Both morphs of the mimic species were marked and released, and their survival was monitored in the following days. The mimic that matched the common model survived best. Right: In another locality, the model species H. sapho is more common. The same procedure used in the first experiment showed that again the mimic that matched the locally abundant model survived best. This second experiment confirms that a mimic's survival rate was determined by whether it matched the model that was most frequent, not by an intrinsic advantage of one mimic color pattern over the other.
Increased complexity = _____ presence of non-coding DNA
increased complexity = increased presence of non-coding DNA
In eukaryotes, recombination occurs during meiosis. Loci that are carried on different chromosomes recombine by the _________ ________ of those chromosomes. Recombination happens between loci on the same chromosome by _______ _____, which joins together a piece of a chromosome inherited from the mother with a piece inherited from the father.
independent assortment, crossing over
Epistasis
is the situation in which the effect of an allele at one locus depends on the allele at a second locus. If some combinations of alleles have high fitness, selection will generate linkage disequilibrium between them
What does Ne * s determine?
it determines determines if mutation is neutral, deleterious, or beneficial
Why might having a smaller genome be adaptive?
less energy to copy DNA during reproduction and potentially less errors/mutations
In eukaryotes, recombination occurs during
meiosis
A selective sweep occurs when:
natural selection causes a beneficial mutation to become rapidly fixed in a population, eliminating variation near that locus in other individuals
kin selection theory
predicts that the degree of altruism depends on the number of genes shared by individuals
Individual A could help individual B collect food. As a result, individual A would produce 4 less offspring, but individual B would produce 12 more offspring. If they are ¼ related, would you expect an allele responsible for this behavior to persist?
rB > C Yes
What does recombination do?
randomizes the combinations of alleles at two loci. one locus is shown as an oval and the other as a diamond. These loci may be on the same chromosome or on different chromosomes. Two different alleles are indicated by the different colors. The offspring makes two kinds of gametes (sperm): those that have not recombined the alleles inherited from the parents (left), and those that have (right). The recombination rate, r, is the fraction of gametes that have recombined alleles.
an example of selective sweep occuring in domestic corn
selective sweep that occurred during the domestication of corn. The ancestor of corn, which looked very much like the living teosinte plant, was short and bushy. Domestication in Central America roughly 10 thousand years ago selected for corn plants that branched less. This favored a mutation in a region of chromosome that regulates expression of the gene tb1, which controls shoot branching. As the mutation spread, heterozygosity nearby on the chromosome was drastically reduced. Other evidence pinpoints the mutation in a noncoding region about 60 kb upstream (to the left) of tb1 [2]. (After [3].)
What sources of evidence do we use to test for selection?
signature of selective sweeps and DN/DS ratio
Semelparous
single reproductive episode before death
phenotypic variance
the amount of variance among the phenotypes
genetic variance
the amount of variation among the averages of the different genotypes
environmental variance
the average amount of variation among individuals with the same genotype
Red Queen Hypothesis
the hypothesis that sexual selection allows hosts to evolve at a rate that can counter the rapid evolution of parasites or Two species in a predator-prey relationship will constantly struggle to keep up with each other's advances in an evolutionary race
reaction norm
the pattern of phenotypic plasticity exhibited by a genotype
recombination rate
the probability that recombination occurs between a given pair of loci recombination rate = r The recombination rates between three pairs of loci. A pair of loci that are close together on the same chromosome have a low recombination rate (here, r = 0.03). A pair that is far apart on the same chromosome has a high recombination rate that approaches 0.5 (here, r = 0.4). A pair of loci on different chromosomes has the maximum possible recombination rate, r = 0.5.
fecundity
the quantity of gametes produced by an individual.
Kin Selection and Hamilton's Rule
the relatedness of each parent to each child, and each child to each parent is: r = ½ relatedness to your grandchild is: r = ½ * ½ = ¼
selective interference is severe in asexual populations because
there is no recombination
cost of reproduction
trade-off between reproduction and all other functions maintaining an organism
gene family
two or more different genes within a single species that are homologous to each other because they were derived from the same ancestral gene
When does hitchhiking occur?
when a mutation genetically linked to that beneficial mutation also becomes fixed (an example of indirect selection)
purifying selection
when disadvantageous alleles decline in frequency
When does a selective sweep occur?
when natural selection causes a beneficial mutation to become rapidly fixed in a population, eliminating variation near that locus in other individuals
Hamilton's rule
when rB > C r = relatedness (chance the altruistic allele is in the relative) B = fitness benefit to the recipient C = fitness cost to the actor Individuals should be altruistic if: the cost (C) to the actor is less than the benefit (B) to the recipient multiplied by their relatedness (r).
selective interference can occur occur in sexual populations because
within a species, some parts of the genome have high recombination rates, while others have low rates.
Patterns Created By Co-Evolution
• "Coupled" means two-way causal interactions between variables • Correlated variation in species' traits • Correlated phylogenetic trees for groups of co-evolving species
What do we mean by a change in evolutionary function?
• A trait has an evolutionary function if its existence in a population is explained by a history of selection for an effect of the trait
How can cooperation be sustained when cheaters prosper?
• Group selection: how many new groups are made, how many groups die • Kin selection • Reciprocity • Tit-for-Tat (debt-based transfers) • Need-based transfers
Peto's Paradox
• If all mammalian cells are equally susceptible to oncogenic mutations, then cancer risk should increase with body size (number of cells) and species life span (number of cell divisions). • The Peto paradox describes the observation that cancer incidence across animals does not appear to increase as theoretically expected for larger body size and life span
Change in evolutionary function therefore involves:
• Trait first acquires one (or more) evolutionary function(s) • A mutation appears modifying the trait and creating a new beneficial effect • Selection for this new effect drives the modified trait to fixation
what are the major mechanisms for gene duplication?
• Unequal crossing-over • Duplicative (DNA) transposition • Retrotransposition • Polyploidization
Benefits to Having Recombination
•Accelerate evolution by generating new combinations of traits •Escape declining fitness from Muller's ratchet •Break co-evolved adaptations among predator and prey species
what are the benefits to having recombination?
•Accelerate evolution by generating new combinations of traits •Escape declining fitness from Muller's ratchet •Break co-evolved adaptations among predator and prey species
Muller's Ratchet (a form of selective interference)
•Asexual organisms are forced to pass down deleterious mutations to their offspring along with the beneficial ones • Without a way to eliminate these negative mutations, they accumulate and the average population fitness declines • Recombination allows separation of negative and beneficial mutations, stopping this ratchet effect
How do these two variables affect the effectiveness of natural selection to purge non-functional DNA? •Selection coefficient •Population size
•Really big populations will be better able to eliminate even weakly deleterious DNA, small selection coefficient causes the DNA to be lost (perhaps suggesting why things like bacteria have low proportions of non-coding to coding DNA (5-10% is non-coding). • Small effective population sizes, weakly deleterious DNA need a larger selection coefficient to get rid of (e.g., humans and why we have more non-coding regions).
