BIO 345 Test 2
Which of the following statements most accurately describes what evolutionary biologists mean by "the cost of producing males" in sexually reproducing organisms?
In a population consisting of both sexuals and asexuals, the number of asexually reproducing individuals should grow more rapidly than the number of sexually reproducing individuals. In sexual reproduction, the role of males is to inseminate females rather than to reproduce directly, so population growth rate is limited by the ratio of females to males. In contrast, an asexual population does not depend on having two types of individuals (males and females).
Which of the following statements best explains how anisogamy differs from isogamy in terms of parental investment in offspring biomass?
In an isogamous system, both sexes contribute to offspring biomass, whereas in anisogamy, only females make this gametic investment Females are defined as the sex that produces few large gametes in an anisogamous system.
prokaryote
- evolved 3 bya - DNA a single circular chromosome - cells smaller than 10µm - basic cell division by binary fission - contains no internal membranes - never multicellular - genetic exchange by unidirectional transfers of fragments of DNA
sequenced entire genome of bacteriophage MS2
Fiers et al.
Which mutation is most common for E. coli?
G-to-A and C-to-T transitions
sequenced first entire DNA genome
Sanger et al.
apomixis
a form of asexual reproduction in which daughter cells are genetically identical to the parent cell In apomixis, there is no fertilization, and daughter cells are produced by a form of cell division that does not reduce chromosome number.
automixis
a form of asexual reproduction in which meiosis generates haploid gametes that fuse with other gametes produced in the same meiotic event
apomixis
a form of asexual reproduction in which there is no fertilization and daughter cells are produced by a form of cell division that does not reduce chromosome number
amphimixis
a form of sexual reproduction in which meiosis generates haploid gametes that fuse with other such gametes formed by a different individual to produce diploid offspring
meiosis
a series of two cell divisions that generates haploid gametes
Daphnia (water fleas) receive an antipredatory benefit from economy of scale in the presence of their predator, Gasterosteus aculeatus (sticklebacks). Which of the following scenarios reflects this benefit?
downward line The larger the group of Daphnia, the more difficult it is for sticklebacks to single out prey. Individuals participating in group living often benefit from economies of scale.
Collectively, a pack of wolves can bring down much larger prey than any single member of the wolf pack can. What does this example illustrate?
economy of scale This arises when a group can achieve a goal that no member of the group could accomplish alone.
diploid
having two copies of each type of chromosome
Drag each statement to the correct box to indicate whether it is true or false of how anisogamy translates into different selective pressures on males and females.
TRUE: - In a system that does not involve effective parental care of offspring as a factor in the success of those offspring/matings, we expect males that mate with numerous females to leave many more offspring than males that mate with few females. - We expect males to compete for access to mates and for females to be more discriminating than males about mate choice. FALSE: - Mating success is typically more variable in females than in males. - We expect females that mate with numerous males to leave many more offspring than females that mate with few males.
segregation distorters (meitotic drive alleles)
alleles that bias the process of meiotic segregation in their own favor, increasing their representation to more than half the gametes produced by an individual
altruism
an action that has the immediate consequence of reducing an individual's own fitness while increasing the fitness of another
free-rider
an individual that takes advantage of others' cooperative or prosocial behavior without contributing any effort or expense to itself
cooperation
an outcome of some interaction in which two individuals each receive a net benefit from their joint actions
trasposons
are genetic elements that move within and between genomes
G-value paradox
arises from the lack of correlation between the number of protein-coding genes among eukaryotes and their relative biological complexity
as genome size increase, recombination rate decrease
as genome size decreases, recombination rate increases
dove-hawk game
both choose hawk: after fighting they both get 1/2 of the resources one selects hawk and one selects dove: hawk gets resource, dove retreats and gets nothing both select dove: they share resource
polygynandry
both males and females have multiple mating partners
prisoner's dilemma
both prisoners agree to testify: serve 3 years both refuse to testify: serve 1 year one testifies, one doesn't: testifier walks free, the other one serves 5 years
Female isopods in the species Hyalella azteca prefer to mate with males that have large gnathopods, with which the males grasp the females and hold them for an extended period during mating. Based on the information in the graph and your understanding of sexual selection, which model of intersexual selection most likely explains the evolution of large male gnathopods? Note that male body size is positively associated with gnathopod size.
direct benefits, because females that choose males with large gnathopods gain a survival advantage Under the direct benefits model, female preference for a male trait is selectively favored because it is associated with a male's ability to enhance her ability to produce offspring rather than with any genetic contribution the male will make to his offspring.
What mode of selection favors the evolution of anisogamy?
disruptive
In applying kin selection theory to the evolution of alarm calling in Belding's ground squirrels, the sexes most likely differ in which variable from Hamilton's rule?
r Remember that Hamilton's rule posits that altruistic behaviors can evolve via natural selection when rb > c. Because females do not disperse from their natal populations, they live in close proximity to kin, and their alarm calls are more likely to alert close relatives to danger than are calls from males.
Nash Equilibrium
strategies for player 1 and player 2 such that neither player can benefit from unilaterally changing his strategy 2 strategies: - player 1 always plays hawk and player 2 always plays dove, neither can benefit by switching his strategy alone - player 1 plays dove and player 2 plays hawk
When does the prisoner's dilemma game predict that cooperation will be an advantageous strategy?
when the game is iterated and there is uncertainty as to the number of rounds two interacting individuals will play against each other
sib-sib conflict
which sibling receives the most resources from the parents
Imagine a hypothetical marine animal population that produces a range of gamete sizes as shown in Panel A. Members of this species release their gametes into the water, and pairs of gametes fuse upon encountering each other. The relationship between zygote fitness and zygote size, shown in Panel B, indicates that the fittest zygotes would result from fusion of two large gametes. However, if we assume a ___ between the number and size of gametes that an individual can produce, and if large gametes are the ___ motile, the probability that two such gametes will find each other is low. Under these conditions, ___ selection is expected to favor the evolution of two classes of gametes, a condition known as ___.
1) trade-off 2) least 3) disruptive 4) anisogamy
Male Drosophila transfer accessory gland proteins along with sperm during normal mating. Experiments implicate these proteins in sexual conflict because they increase female egg production but decrease female survival. If accessory gland proteins are responsible for depressed female survival, which of the treatments shown in the table below must have generated the curve marked with an arrow? Assume that none of the males could produce sperm.
A In Treatment A, males produced accessory gland proteins and could transfer these proteins during normal mating, so females in Treatment A would have been the only ones receiving these proteins and suffering reduced survival as a consequence.
direct benefits
Selection favors females that choose mates based on traits associated with resource provisioning rather than genetic contributions to offspring.
good genes
Selection favors females that choose mates with traits that are honest indicators of genetic quality.
FIsherian runaway selection
Selection favors females with a preference for a male ornament that is in linkage disequilibrium with the genes underlying the female preference. The advantage to a female under this model is the production of sons that females prefer to mate with, which is why it is sometimes called the "sexy sons" mechanism of female choice.
sensory bias
Selection favors male traits that tap into a preexisting female sensitivity to some stimulus.
Which of the following conclusions most directly follows from the data shown in the figure?
Sneaker males produce sperm that are more numerous but of lower quality than sperm produced by the parental males with which they compete to fertilize a female's eggs
Drag each statement to the correct box to indicate whether it is true or false of the hawk-dove game as a model of animal conflict. Assume that there are cues that allow individuals to know who is Player 1 and who is Player 2.
TRUE: - If the value of the resource under dispute exceeds the cost of injury, there is a Nash equilibrium when both Player 1 and Player 2 always play H. - If the cost of injury exceeds the value of the resource under dispute, there is a Nash equilibrium when Player 1 always plays H and Player 2 always plays D. FALSE: - If the value of the resource under dispute exceeds the cost of injury, there is a Nash equilibrium when Player 1 always plays H and Player 2 always plays D.
The critical events that have changed the way life is organized:
- The origin of self-replicating molecules capable of heredity. - The transition from RNA as both catalyst and genetic material to a division of labor with proteins as catalysts and DNA as genetic material. - The origin of the first cells - The emergence of eukaryotic cells - The evolution of sexual reproduction - The evolution of multicellular organisms from single-celled organisms - The evolution of developmental complexity within multicellular organisms - The evolution of individuality, including the evolution of germ cells, a specialized line of cells that became gametes. - The evolution of groups, including complex societies - The evolution of eusocial societies, like those seen in some species of bees, ants, and wasps, with a division of labor and sterile castes.
Which percentage represents the total percentage of transposable elements in the human genome?
44.7% LINE and SINE elements, along with other transposons, are the largest proportion of the human genome.
You analyzed the genome of an unidentified organism using cells provided to you. If the genome size was 10^1 Mb and there were 10^0 Mb of coding DNA, approximately what percentage of the genome would you predict is noncoding DNA based on the graphed data?
90
Identify whether each statement on the left is true of sexual reproduction, asexual reproduction, or both.
ASEXUAL: - Deleterious mutations build up irreversibly due to Muller's ratchet. - Deleterious mutations are associated with reductions in fitness. SEXUAL: - An individual in which a deleterious mutation arises can produce offspring that do not have that mutation. - Deleterious mutations are associated with reductions in fitness. Recombination counteracts the "ratchet," whereas the number of deleterious mutations in a genome can only increase in asexual populations.
runaway sexual selection
An extreme case of the Fisher process of sexual selection in which positive feedback between genes that code for male traits and genes that code for particular mating preferences in females drives the evolution of highly exaggerated male traits and strong female preferences for them.
Which of the following are benefits of slug formation to individual amoeboid cells of Dictyostelium discoideum?
BENEFITS: - increased mobility - formation of an antipredatory slime sheath - increased ability to respond to environmental cues - increased dissemination of spores from elevated fruiting bodies NOT BENEFITS: - ability to consume larger prey - increased tolerance to antibiotics
sequenced first genome of a multicellular organism
C. elegans Sequencing Consortium
Drag each statement to the correct box to indicate whether or not it is a contention of the neutral theory of molecular evolution.
Contention of the Natural Theory: - Most of the genetic variation that persists long enough to be measured in a population is neutral. - Most evolutionary substitutions that persist long enough to be measured in a population are neutral. Not a contention of the natural theory: - The ratio of silent to nonsilent changes in a coding region of DNA is the same across all codons. - Natural selection does not act at the molecular level. - We see neutral evolution in noncoding regions of a DNA sequence, but not in regions that encode proteins.
Which genome characteristic enables some viruses to undergo recombination, and why is this beneficial?
Diploid genome; this genome can rapidly generate genetic diversity through recombination
In which way would understanding the origin of the apicoplast most likely have utility outside of evolutionary study?
Disruption of the apicoplast function in Plasmodium may provide a safe cure for malaria
Which of the following represent evidence for the endosymbiotic origin of chloroplasts and mitochondria?
EVIDENCE: - RNA-coding genes similar to cyanobacteria and proteobacteria, respectively - organelle genomes consisting of a single circular chromosome NOT EVIDENCE: - the ability of organelles to maintain life independently of the cell - the presence of a nucleus within these organelles - division of organelles by mitosis, as in the nuclear genome
sequenced first whole genome sequence for an independently living organism
Fleischmann et al.
sequenced first genome of a eukaryote
Goffeau et al.
completed Homo sapiens genome
Int'l Human Genome Sequencing Consortium
For which reason does recombination in sexually reproducing organisms prevent the accumulation of deleterious mutations via Muller's ratchet?
It breaks up haplotypes and can combine chromosomal segments containing beneficial alleles With recombination between parental chromosomes, it is possible to generate an offspring genome that contains fewer deleterious alleles than in either parental chromosome.
colony of small, motile cells that do not reproduce
Mutation causes constitutive expression of regA in a cell that gives rise to a colony.
deciphered the genetic code by matching each RNA codon to its amino acid
Niremberg and others
Which of the following conclusions are reasonable interpretations of this phylogeny showing the living arrangement of cells for extant eukaryote groups?
REASONABLE CONCLUSIONS: - The common ancestor of Rhizaria was unicellular. - Within the Plants clade (inclusive of algae), there are at least two transitions from unicellularity to multicellularity. - Groups comprising both multicellular and unicellular organisms include brown algae, fungi, and red algae. NOT REASONABLE CONCLUSIONS: - The most recent common ancestor of all slime molds was multicellular or colonial. - The earliest origin of multicellularity is in the chlorophyte algae. - Multicellularity always passes through a phase of coloniality.
The freshwater crustacean Daphnia magna is a cyclical parthenogen in which individuals normally reproduce asexually but occasionally reproduce sexually. Experiments have demonstrated that females shift to sexual reproduction in response to introduction of a new predator, a decrease in food quality, and cues related to drying up of a temporary pond. Drag each of the statements below to indicate whether it is true or false of these reproductive shifts in Daphnia.
TRUE: - These results are consistent with the hypothesis that sexual reproduction confers an advantage in temporally variable and unpredictable environments. - When the environment is stable, asexual reproduction allows a well-adapted lineage to grow at a higher rate than a similarly adapted sexual lineage. FALSE: - A shift to sexual reproduction decreases the ability of a population to respond to new selection pressures and is thus a puzzling phenomenon in Daphnia.
Which of the taxonomic groups shown in this graph have members with less than 10% coding DNA in their genome?
TRUE: - animals - land plants FALSE: - unicellular eukaryotes - viruses - prokaryotes
The graph depicts the association between sexual reproduction and parasite load in lake and stream populations of the snail Potamopyrgus antipodarum, which can reproduce either sexually or asexually. The study that generated the data was designed to test hypotheses regarding the evolutionary advantage conferred by sexual reproduction. Drag each statement to the correct box to indicate whether it is true or false of the results in the graph.
TRUE: - Sexual reproduction is more common in lake populations than in stream populations, as predicted by the multiple niche hypothesis. - The results of this study are not consistent with the predictions of the environmental unpredictability hypothesis. FALSE: - Greater parasite load is associated with less sexual reproduction, as predicted by the Red Queen hypothesis. These lakes have more ecological niches than the streams, and sexual reproduction increases genetic diversity in a population. The multiple niche hypothesis predicts that greater niche diversity should be associated with a higher frequency of sexual reproduction in a snail population. Under the environmental unpredictability hypothesis, sexual reproduction is favored under less predictable environmental conditions, and should thus be more prevalent in streams than in lakes. Look again at the figure to see if this is the observed pattern.
According to Maynard Smith and Eörs Szathmary, which of these events characterize most major evolutionary transitions (such as the emergence of eukaryotic cells or the evolution of multicellularity)?
TRUE: - increased efficiency of acquisition, processing, transmission, and storage of information - aggregation of individuals into groups that share reproductive efforts - change in economies of scale and efficiency of specialization associated with aggregation FALSE: - evolution of more complex sensory and cognitive systems - increased trophic specialization or narrow adaptation for a primary prey group - freedom from selective constraints with increasing dependence on technology
What does the neutral theory of molecular evolution contend?
The majority of changes in DNA sequence arise due to genetic drift and have no impact on phenotype.
What is the relationship between genome size and number of protein-coding genes in different types of bacteria?
The number of protein-coding genes increases linearly with genome size in bacteria.
twofold cost of sex
The observation that—with all else equal—an asexual lineage introduced into a population of sexually reproducing organisms would initially double in representation in each generation.
Select the statement that most accurately explains the differences between these paired phylogenies.
The phylogenies in Pair A represent a set of sexually reproducing species, and the phylogenies in Pair B represent a set of asexually reproducing species. The mitochondrial and nuclear phylogenies are more congruent for asexual species because both types of DNA are maternally inherited in asexual reproduction.
The figure depicts the fitness increase in sexual (orange) and asexual (green) strains of yeast grown under stressful environmental conditions. Which feature of the graph most directly supports the Fisher-Muller hypothesis of adaptive evolution?
The sexual lineage increases in fitness more quickly than the asexual lineage. The Fisher-Muller hypothesis posits that sexual reproduction accelerates natural selection because recombination assembles favorable combinations of beneficial alleles more rapidly than does mutation in asexual lineages.
The genomes of viruses are characterized by their diversity and compactness. There is also variation in their genetic material, ranging from DNA-based genomes to RNA-based genomes, each of which can be single- or double-stranded. The type of genetic material a virus has determines how it replicates that genetic material. Match each type of viral genome with its correctly transcribed product. Viral code: 5' UUGAUGUGCCCAGCC
UUGAUGUGCCCAGCC - single-stranded, positive-sense RNA virus AACUACACGGGUCGG - single-stranded, negative-sense RNA virus AACTACACGGGTCGG - retrovirus
genomic imprinting
alleles are differentially expressed according to whether they are inherited from the mother or from the father
efficiencies of specialization
arise because once groups are collectively engaged in a task, they can benefit not only from larger numbers, but also from a division of labor, allowing different individuals to specialize in different tasks
economy of scale
arises when a group can perform a task more efficiently than a single individual or when a group can do things that a lone individual cannot do at all
nutrient poor environment
gene expression: rls1 expressed resource allocation: survival
nutrient rich environment
gene expression: rls1 not expressed resource allocation: reproduction In an environment with sufficient resources, cells begin to reproduce.
sensory bias model
hypothesizes that females initially prefer a certain male trait but nt because of ny mating benefit, direct or indirect, is associated with that trait. instead, it proposes that female nervous systems respond to trait M either because it is associated with some benefit outside of mate choice or simply as an artifact of how the stimulus excites their nervous systems
syngamy
the union of gametes from different individuals during sexual reproduction Syngamy produces a diploid zygote that inherits a set of chromosomes from each parent.
Which of the following predictions of the Red Queen hypothesis is most strongly and directly supported by the results shown in the figure? The gold bars in the graph represent the frequency of the asexual lineage, and the red line represents the frequency of all parasites in a natural population.
there will be a time lag between the appearance of host resistance and the evolution of a mechanism by which the parasite can overcome that defense
apomixis
unfertilized gametes are produced by mitosis-like cell division, producing daughter cells with an unreduced number of chromosomes. genetically identical to those of the mother, referred to as apogamy in plants
sexual dimorphism
when sexual selection acts on males and females in the same population, it leads to sexual dimorphism, a difference in how the same trait manifests in males and females
eukaryote
- basic cell division by mitosis - evolved 1 to 2 bya - cells larger than 10µm - often multicellular - contains membrane-bound organelles - DNA arranged in multiple linear chromosomes - genetic exchange through meiosis and fusion of gametes
sexual reproduction favored:
- high environmental unpredictability - high number of niches - high parasite load
Place in order the events that led to the apicoplast, an organelle of the Apicomplexa.
1) A cynobacterium became a primary endosymbiont in a eukaryotic cell 2) the cyanobacterium lost ancestral photosynthetic function and gained integrated function with the nucleus 3) in a secondary endosymbiosis, the eukaryotic cell was engulfed by an ancestor of Apicomplexa 4) the nucleus of the secondary endosymbiont was lost, leaving a structure called apicoplast that is retained within four membranes
Horizontal gene transfer is the movement of genetic material from organisms to another by transduction, transformation, or conjugation. In transformation, a cell takes up DNA from the environment. Place the steps of transformation in the correct order.
1) Bacterial cell encounters free DNA in the environment 2) Cell takes in some of the DNA fragments 3) Some of the new DNA fragments are incorporated into the chromosome by recombination
Place in order the events that lead from single amoebas to the formation of a Dictyostelium discoideum slime mold slug and its eventual sexual reproduction.
1) amoeboid cells occupy a region of soil where food has become scarce 2) cells emit cAMP 3) cells drawn to the region begin to adhere to each other, sticking to cAMP-emitting cells 3) when enough cells have joined together, the slug experiences heightened mobility and defense from predators 4) the mobile slug migrates to the soil surface 5) cells in the slug begin to differentiate into a vegetative stalk and a fruiting body
The production of gametes of two different masses in sexually reproducing species is called ___. Under such a system, only the ___ sex invests in offspring biomass. In asexual reproduction, all individuals in the population invest completely in offspring production, and as a consequence, we expect an asexual population to grow ___ than a sexual population. Evolutionary biologist John Maynard Smith called this cost of producing males and the effects on population growth rate "the twofold cost of sex."
1) anisogamy 2) female 3) faster
To eventually become selectively advantageous at the ___ level, an adaptation must first provide fitness benefits at the ___ level.
1) group 2) individual
Red Queen Hypothesis
if parasites infect an asexual lineage, the parasites are likely to be very successful after a relatively small number of generations because in each generation their host's genome remains largely unchanged as a result of asexual reproduction
isogamy
individuals in a population produce one type of gamete -- each parent produces mid-sized gametes that, when they fuse, are together the size of the large gametes produced by anisogamous females
intersexual selection
individuals of one sex select among individuals of the other sex as mates
intrasexual selection
members of one sex compete with each other for mating access to the other sex
single cell that remains small and produces flagella
regA is expressed in a cell.
colony of large, immotile cells that sink in water
regA is knocked out of a cell that gives rise to a colony.
single cell that grows but doesn't produce flagella
regA is not expressed in a cell.
no regA expressed
reproductive cell When regA expression is suppressed, cells grow large and serve the reproductive function of the colony.
endosymbisis
symbiosis within a cell
anisogamy
the production of two different kinds of gametes that are usually called sperm (small gametes) and eggs (large gametes). only females invests in offspring biomass
The neutral theory predicts that the neutral substitution rate equals the neutral mutation rate and is independent of population size. This theory predicts a molecular clock that ticks at a constant rate per ____. However, many studies have revealed rates of molecular divergence that are proportional to absolute time even among species with dramatically different generation times. Tomoko Ohta developed a theoretical solution to this puzzle with her ____ theory, which posits that most substitutions are not truly neutral but actually slightly deleterious and thus subject to both genetic drift and ____ selection. Weak selection dominates over drift only in populations above a certain size; in smaller populations, even deleterious mutations evolve as if they are neutral. The nearly neutral theory thus predicts that substitution rate per generation is ____ in smaller populations. The clock ticks at a constant rate with respect to absolute time because species with small populations also tend to have long generation times, and the effects of population size cancel out.
1) generation 2) nearly neutral 3) purifying 4) higher
True sexual reproduction involves recombination, production of haploid gametes via the cell division process known as ___, and gametic fusion, or syngamy. These steps, which as a whole make up the process called ___, produce a diploid zygote with a set of chromosomes inherited from each parent. Species that only reproduce asexually are ___ among eukaryotes, and asexually reproducing lineages typically go extinct more ___ than sexual lineages over evolutionary time.
1) meiosis 2) amphimixis 3) rare 4) quickly
Horizontal gene transfer is the movement of genetic material from one organism to another by transduction, transformation, or conjugation. In transduction, a phage packages bacterial DNA instead of its own within its capsule. Place the steps of transduction in the correct order.
1) phage attaches to bacterial host and injects its DNA 2) Cell produces new phage components 3) host DNA is mistakenly packaged into some viral capsids 4) cell bursts, releasing phage particles 5) phage carrying host DNA injects that DNA into a new bacterial host 6) transduced DNA is incorporated into the new host's genome by recombination
Viruses exhibit a tremendous amount of compression in their genomes with the ability to pack multiple genes within the same region on a genome. Overlapping is one way viruses pack multiple genes into the same region. Using the same reading frame but starting in a different position _____, , while changing the reading frame ____. This produces multiple ___ from a single region of the genome.
1) results in a different amino acid sequence 2) changes the amino acids in the sequence 3) proteins
Benefits of sexual reproduction
1) sexual reproduction purges deleterious mutations 2) sexual reproduction generates genetic variation, some of which is responsible for traits favored by natural selection
trade-off between the size of gametes and the number of gametes
1) the larger the gamete, the smaller the number of gametes an individual can produce 2) the larger the size of a gamete, the less mobile it is 3) the probability that a zygote survives increases with its size
Order the major transitions in a way that could represent a logical flow of evolutionary events.
1) the origin of self-replicating molecules capable of heredity 2) the origin of the first cells 3) the emergence of eukaryotic cels 4) the evolution of multicellular organisms from single-celled ancestors 5) the evolution of germ-line cells 6) the evolution of groups of multicellular organisms 7) the evolution of eusocial societies
Muller's ratchet
process by which the number of deleterious mutations builds up irreversibly over evolutionary time in asexual populations
automixis
production of haploid gametes via meiosis, but diploidy is usually restored by the fusion of haploid nuclei from the same meiosis. genetically different from their parent and their siblings, much less genetic variation is generated than in sexual reproduction.
regA expressed
somatic cell Cells expressing regA do not grow large or divide.
Fisher process
some females express a preference for an ornament, and simply because of this preference, selection favors both the male ornament and further female preference for it
How is understanding the role of rls1 in unicellular Chlamydomonas reinhardtii useful in understanding the evolution of multicellularity in volvocine algae?
the C. reinhardtii gene rls1 is homologous to a gene that determines cell identity in Volvox In C. reinhardtii, rls1 controls reproductive versus survival behavior of cells in response to nutrient availability.
Drag each statement to the correct box to indicate whether it is true or false as you consider the information in the graph depicting the results of a competition experiment with sexual and asexual snails.
TRUE: - These experimental results illustrate what Maynard Smith called the "twofold cost of sex." - We can assume that the asexual snails used in the experiment were female. FALSE: - If the experimenters were to grow these snails in the presence of parasites for multiple generations, we would expect essentially the same outcome. - These experimental results illustrate the evolutionary advantage of anisogamy.
Drag each statement to the correct box to indicate whether it is true or false of the phylogenetic distribution of sexual and asexual reproduction in eukaryotes.
TRUE: - Almost no multicellular eukaryotic taxa consist entirely of asexually reproducing species. - Few eukaryotes reproduce only asexually. FALSE: - Modern eukaryotes that reproduce asexually most likely retain the ancestral reproductive mode of eukaryotes. - Sexual taxa tend to go extinct more quickly than asexual taxa.
amphimixis
sexual reproduction which involves alternating phases of meiosis and gamete fusion 3 steps: 1) recombination - the crossover between homologous chromosomes, which produces new chromosomal variants 2) gamete production: production of haploid gametes by diploid individuals via reductive meiotic division 3) gamete fusion - gametic exchange between individuals, in which haploid gametes fuse to produce a diploid offspring
Sexual reproduction is associated with costs. Indicate which of the following statements is/are consistent or inconsistent with this statement.
CONSISTENT W/ STATEMENT: - Sexually reproducing organisms incur an energetic cost associated with finding and courting potential mates. - Sexually reproducing individuals pass on a smaller proportion of their genes to each offspring than do asexual individuals. - Recombination associated only with sexual reproduction can break up favorable allelic combinations/haplotypes. INCONSISTENT: - The number of sexually reproducing individuals in a population should grow more rapidly than the number of asexually reproducing individuals. There is a benefit to recombination in terms of genetic variation, but it can act in opposition to natural selection if it breaks up advantageous haplotypes.
Which of the following statements about the C-value and C-value paradox are correct?
TRUE: - Genome size does not directly correlate with the number of protein-coding genes. - Genome size does not obviously correlate with an organism's phenotypic complexity. - Researchers discovered that the amount of DNA per cell varies widely across living organisms. FALSE: - There is little variation in genome size within taxonomic groups.
The figure shows the hypothetical results of an experiment testing for parent-of-origin conflict due to genomic imprinting. Which of the following conclusions is most likely given these results?
There is maternal imprinting but not paternal imprinting. In maternal imprinting, genes on maternal chromosomes are silenced, and genes on paternal chromosomes are expressed. In this case, the embryo is inviable only when there are two copies of the maternal chromosomes, suggesting that two silenced copies of crucial genes are present in the zygote.
polygyny
one male lives and mates with multiple females but each female only mates with a single male
inclusive fitness
the sum of indirect and direct fitness, inclusive fitness servs as a measure of the total contribution that an individual makes toward producing copies of its genes in the next generation, whether in its own descendants or in those of its relatives
Because siblings are close genetic relatives, an offspring's ___depends both on its own survival and reproduction and on the fitness of its brothers and sisters. An offspring thus benefits from direct parental care as well as from the care a parent directs toward a sibling, though an offspring gains more from direct care than from care directed at siblings. A parent, however, is equally related to all of its offspring. These conditions generate ___such that an offspring is selected to extract more resources from a parent than the parent is selected to invest.
1) inclusive fitness 2) parent-offspring conflict
Sexual selection is a type of selection in which traits found in one sex increase in frequency as a consequence of their beneficial effects on ___ alone. ___ selection results in the increase in the frequency of traits that favor the ability of members of one sex, typically males, to directly compete with each other for access to mates. This type of selection is often implicated in the evolution of male weapons and armor. ___ selection results in the increase in the frequency of traits that favor the ability of members of one sex to choose among members of the other sex. This form of selection is sometimes called "female choice" because females pick mates based on some aspect of male phenotype such as color or ornamentation. Both forms of sexual selection are associated with the evolution of ___, in which males and females differ in phenotype.
1) mating success 2) intrasexual 3) intersexual 4) sexual dimorphism
The potential reproductive success of the most successful males in a population depends on social structure and mating system. Place the following mating systems in increasing order of potential male reproductive success (from lowest to highest).
1) polyandry 2) monogamy 3) polygynandry 4) polygyny
Evolutionary conflict can occur below the individual level when an allele in a heterozygote generates a bias that causes it to be represented in more than half of the individual's gametes. The process whereby this biased distribution happens is called ___. Another form of conflict within an individual's genome occurs when there is ___, whereby specific alleles inherited from either the father or the mother are modified such that the parent from whom a chromosome originated determines gene expression and function.
1) segregation distortion 2) genomic imprinting When a gene is paternally imprinted, it is expressed when present on the maternal chromosome and silenced when present on the paternal chromosome.
The graph below depicts how costs to parents and benefits to a focal offspring change as the level of parental investment in that particular offspring increases. Click on the arrow in the graph that represents the cost-benefit difference that the focal offspring is selected to maximize.
An individual receives inclusive fitness benefits from direct parental investment as well as from parental investment in siblings. However, the focal offspring is 100% related to itself but only 50% related to each of its siblings. Therefore, offspring are selected to extract a level of direct parental investment that maximizes the difference between the benefit to themselves and half the cost to the parents.
Why does the cost-benefit difference decrease for a focal offspring as direct parental investment increases above the optimum level (from that individual offspring's perspective)?
Beyond that level of investment, the cost to the parent compromises its ability to invest in other offspring to the point that there is no longer a benefit to the focal offspring in terms of indirect fitness
Drag each statement to the correct box to indicate whether or not it is a distinction between the good genes model and the Fisherian runaway model of sexual selection.
DISTINCTION: - Both the good genes model and the Fisherian model predict linkage disequilibrium between loci associated with female preference and loci that govern the male trait. NOT A DISTINCTION: - The good genes model is an example of intersexual selection, whereas the Fisherian model is an example of intrasexual selection. - The good genes model predicts that male viability will be positively correlated with male ornamentation, whereas the Fisherian model predicts a negative correlation between ornamentation and viability. - Both the good genes model and the Fisherian model assume that the preferred male trait covaries with some other indicator of male genetic quality.
Order the payoffs in the prisoner's dilemma game from lowest to highest.
LOWEST - payoff to an individual that cooperates against an opponent that defects - payoff to an individual that defects against an opponent that defects - payoff to an individual that cooperates against an opponent that cooperates - payoff to an individual that defects against an opponent that cooperates HIGHEST
Drag each of the following statements to the correct box to indicate whether it is correct or incorrect of Petrie's experiments on mate choice in peafowl.
TRUE: - Male offspring of males with more elaborate tails are healthier (heavier) and offspring regardless of sex survive better than offspring of males with less elaborate tails, hypothetically because they have inherited genes that enhance their ability to fight infectious disease. - Because elaborate tails are energetically costly, they are likely honest indicators of male quality, in keeping with Zahavi's handicap principle. FALSE: - Evidence from Petrie's study suggests that elaborate tails in peacocks evolved under intrasexual rather than intersexual selection. - The results shown in the graph indicate that female preference for large eyespots most likely evolved under the direct benefits model since offspring weight (an indicator of health) is positively correlated with the mean size of eyespots in the father.
Drag each statement to the correct box to indicate whether it is true or false of the tug-of-war model for the evolution of genomic imprinting.
TRUE: - The "tug-of-war" for which this model is named occurs between a female that is equally related to all offspring she will produce in her life and a male who is father to her current offspring but not necessarily to her future offspring. - The model predicts that a male should be selected to divert more resources to his current offspring than is optimal from the perspective of his current female mate. FALSE: - In mammals, maternally imprinted genes are typically associated with allocating resources toward increasing embryonic growth rates, whereas paternally imprinted genes are typically associated with decreasing embryonic growth rates. - In mammals, the father is more closely related to any given current offspring than is the female with which he sired that offspring.
Drag each statement to the correct box to indicate whether or not it accurately describes the model depicted in the figure. Low-, medium-, and high-quality males maximize fitness (as indicated by the black curve) by producing tails of the lengths L, M, and H, respectively.
TRUE: - The cost of producing a tail of a given length is relatively lower for a high-quality male than it is for a low-quality male. - This model demonstrates that a costly trait can be an honest indicator of male quality. FALSE: - For any given tail length, females are assumed to prefer a high-quality male over a low-quality male. - The optimal tail length for a male of a given quality is the length at which the cost curve crosses the curve representing the relationship between mating success and tail length. The optimal tail length maximizes the difference between the fitness benefit (mating success) and the fitness cost of producing a tail of that length.
Imagine a model in which the players in a hawk-dove game do not know who is Player 1 and who is Player 2 and the cost of injury is higher than the value of the disputed resource. Drag each statement to the correct box to indicate whether it is true or false of the Nash equilibrium associated with this game.
TRUE: - There is a mixed Nash equilibrium in which each player plays hawk with probability p and dove with probability 1 - p, such that both strategies give the same payoff. - There is a mixed Nash equilibrium in which some fraction p of the population plays hawk and a fraction 1 - p plays dove, such that p = v/c. FALSE: - There is a strict Nash equilibrium in which both players always play dove.
Identify whether each statement correctly or incorrectly reflects the relationship in the graph between mating system and parent-offspring conflict. Assume that we are considering maternal investment in offspring.
TRUE: - Under polyandry, the future offspring of a female's current offspring will not necessarily be full siblings. - For a species in which the mother provides most parental care, inclusive fitness theory predicts that offspring should be selected to extract a higher level of direct parental investment under a polyandrous mating system than under a monogamous mating system. FALSE: - We can use this graph to determine the optimum level of direct parental investment from the perspective of a focal offspring. When the mating system is polyandrous rather than monogamous, we expect an increase in the slope of the red line representing maternal cost relevant to the offspring. The slope of the line would actually become less steep in the case of polyandry, because the "half" in the original line corresponds to a coefficient of relatedness between the focal individual and its full siblings. If future offspring of the same mother are only half siblings, then the line should represent one-quarter of the parental cost.
handicap policy
The handicap principle predicts that males who can survive in spite of the costs of maintaining an elaborate tail are likely to be of high genetic quality.
In mice, the Igf2 gene, which is involved in production of a growth hormone, is maternally imprinted. The Igf2r gene, which is associated with binding and reducing activity of the growth hormone, is paternally imprinted. Which of the following statements best explains why this observation makes sense under the tug-of-war model for the evolution of genomic imprinting?
The optimal level of investment in currently developing offspring is higher for males than for females, so the maternal chromosome expresses a growth-suppressing gene, and the paternal chromosome expresses a grwoth-promoting gene A female is sure to be the mother of all the offspring she produces in her life, but her current mate might not be the father of future offspring.
What is an evolutionarily stable strategy (ESS)?
a strategy that, when common in a population, cannot be invaded by a rare mutant strategy When all individuals in a population play a strategy that is an ESS, no new strategy introduced into the population can increase in frequency under natural selection.
parent-offspring conflict
how parents allocate resources to their offspring conflict that arise because the genetic interests of offspring and their parents are not perfectly aligned
Because they represent competitive strategies rather than traits that serve as criteria for female choice, alternative reproductive morphs, such as sneaker and satellite males in bluegill sunfish, most likely evolve under what type of selection?
intrasexual
What term describes the form of sexual selection in which members of one sex (typically males) compete directly for access to mates?
intrasexual selection
C-value paradox
lack of correlation between genome size and the biological complexity of an organism
monogamy
mating system of one male and one female forming an exclusive social pair bond
paternal imprinted gene
the copy of the imprinted gene from the father is always turned "off," whereas the copy from the mother is always turned "on.
maternal imprinted gene
the copy of the imprinted gene from the mother is always turned "off," whereas the copy from the father is always turned "on.
direct fitness
the expected number of viable offspring an individual produces
germ-soma distinction
the germ line passes genetic information between generations; the soma is the vehicle for germ line transmission, and is shaped by natural selection.
indirect fitness
the incremental effect that an individual's behavior has on the fitness of its genetic relatives when an individual increases the number of its genetic kin that survive and reproduce, it is indirectly getting copies of some of its own genes into the next generation
polyandry
the mating of one female with more than one male while each male mates with only one female
Codon usage bias occurs when a particular codon is used more frequently than others. Scientists have questioned why this occurs and accumulated evidence that points to several reasons for this phenomenon. One area of interest has been the frequency of long mononucleotide repeats. Examine these graphs depicting mononucleotide repeats in E. coli, S. cerevisiae, and C. elegans and then fill in the blanks in the following paragraph. Of the species shown, ___ has the lowest frequency of longer (nine or more repeats) mononucleotide repeats, while ___ has higher frequencies of longer mononucleotide repeats. The bases ___ occur in higher frequencies for longer mononucleotide repeats. Therefore, of these two species, ___ would be predicted to have a ___ resulting in ___.
1) E. Coli 2) S. cerevisiae 3) A and T 4) S. cerevisiae 5) higher rate of replication slippage 6) frameshift mutation
The ___ fidelity associated with DNA proofreading and repair is evolutionarily important because it dramatically ___ mutation rates. fidelity: ability of DNA polymerase to accurately replicate a template
1) higher 2) decreases
Individuals are integrated and ___ wholes that can ___ and pass on to their offspring ___.
1) indivisible 2) reproduce 3) heritable variation
There are several reasons for codon usage bias, and two primary reasons are discussed in this chapter. Examine this chart of codon usage for E. coli O157: H7. Given what you have learned, which tRNA would you expect to be most frequent for this species?
GAC The most commonly used codon is CTG, which codes for leucine, so the complementary tRNA would be GAC (aspartic acid).
Drag each statement to the correct box to indicate whether or not it describes the figure to the right, which depicts the expected evolutionary trajectories of sexual and asexual lineages coexisting with a parasite that has a much shorter generation time than the host.
TRUE: - A new asexual lineage with genetically based defenses against the parasite is at an initial competitive advantage over sexual lineages. - If a mutation arises that allows the parasite to overcome resistance in an abundant asexual host lineage, the asexual clone is at a disadvantage relative to genetically variable sexual hosts. FALSE: - High parasite loads favor asexual reproduction over sexual reproduction in populations where both reproductive modes can occur.
Drag each statement to the correct box to indicate whether or not it reflects the differences between the two figures depicting fixation in a large population with the advantageous mutations A, B, and C. Assume that these three loci are physically linked in the genome.
TRUE: - In Panel 2, the A allele can come together with the B allele in the same haplotype only if B arises in an individual that already carries A. - In Panel 1, the assembly of the most advantageous haplotype involves the breakdown of linkage disequilibrium at the three loci under consideration. - Panel 1 represents sexual reproduction, and Panel 2 represents asexual reproduction. FALSE: - Natural selection fixes the most advantageous haplotype more rapidly in Panel 2 than in Panel 1.
Drag each statement to the box to indicate whether it is true or false of the evolutionary phenomenon known as Muller's ratchet.
TRUE: - Muller's ratchet is the phenomenon whereby deleterious mutations accumulate irreversibly in asexual populations. - Muller's ratchet depends on a genetic system in which deleterious mutations arise and mutations from deleterious back to advantageous alleles are negligibly rare. FALSE: - Muller's ratchet occurs because new deleterious alleles are fixed rapidly in asexual populations. - Muller's ratchet is characterized by fluctuation in the number of deleterious alleles present in an asexually reproducing population.
Drag each statement to the correct box to indicate whether or not it is a likely advantage of sexual reproduction when the environment is spatially or temporally unpredictable.
TRUE: - Production of genetically variable offspring increases the probability that some progeny will be well suited to new environmental conditions. - Production of genetically variable offspring increases opportunities to exploit different niches and could thus reduce resource competition among siblings. FALSE: - A sexually reproducing lineage will grow in number faster than an asexually reproducing lineage that is equally well adapted to the environment.
Overall, DNA-based viruses have much smaller genomes in comparison to eukaryotes and most prokaryotes. How does natural selection act on genome size of viruses? Select all that apply.
TRUE: - Viruses are selected for rapid replication, and the shorter their genome, the faster they can replicate. - Viruses must replicate many times within a host cell, so they must have small capsules, which constrains the size of the genome. FALSE: - The small size of viruses helps them to evade the immune system of the host. Smaller viruses have smaller genomes, and are therefore more successful. - Viruses replicate very slowly, so viruses with shorter genomes are more numerous in a population and are selected for.
Which statements accurately represent the relationship between genome size and coding DNA?
TRUE: - As genome size increases, the percentage of coding DNA decreases. - As a percentage of total genome, organisms with smaller genomes have more coding DNA. FALSE: - As a percentage of total genome, organisms with larger genomes have more coding DNA. - As genome size increases, the percentage of coding DNA increases.
Centromeres are critical to successful replication of the genome in eukaryotic organisms. During cell division, they are critical to the division of replicated chromosomes into each daughter cell. One feature of the sequence that codes for centromeres that is puzzling to scientists is the high rate of evolution observed. Henikoff and his colleagues proposed the "centromere drive hypothesis" to explain this phenomenon. How does this hypothesis explain what they observed?
TRUE: - Selection at the level of the chromosome will favor any mutation to the centromere that increases its chance of segregating to the oocyte. - Genomes that can counter the effects of deleterious centromeric mutations would be favored by selection. FALSE: - Selection at the level of the chromosome will favor any mutation to the centromere that increases its chance of segregating to the spermatozoa. - Genomes that decrease the number of repeat sections associated with the centromere will be more likely to bind to microtubules. Increasing the number of repeat sections associated with the centromere provides a larger target for the microtubules. By increasing the chances of segregation to an oocyte, a centromeric mutation can also increase the probability of meiotic problems.
Ratcliff and colleagues published a series of experiments demonstrating the ability for natural selection to drive normally single-celled yeast to take on multicellular forms. Which of the following findings would have invalidated their conclusions?
WOULD INVALIDATE: - Snowflake clusters generated after 60 generations produce only single cells when not subject to selection in the 61st generation. - Control cultures with no selection for sedimentation eventually produce monocultures of the snowflake type. WOULD NOT INVALIDATE: - Individual cells of snowflake clusters are found to be genetically more similar to each other than cells in other clusters. - Snowflake clusters occasionally divide by means of apoptosis, or programmed cell death. - Populations with high frequencies of snowflake phenotypes give rise to similar descendent populations even when the selective regime is removed.
direct benefits model of sexual selection
selection favors females who have a genetic predisposition to choose mats that provide them with resources -- above and beyond sperm -- that increase their fecundity and/or survival
sexual selection
selection for traits that increase mating success rather than survival
