BIOL 3030- Practice Test Chapter 16

Which of the following is NOT a reason why the twofold cost of sex is sometimes referred to as the "cost of males"?

a. Males do not contribute genes to the next generation. b. Males do not produce new offspring. c. Males invest in sperm, most of which are wasted, rather than biomass. d. Sperm cells do not contribute any substantial energy resources to the eggs they fertilize.

Which of the following is NOT a problem associated with distinguishing the Fisherian sexual selection model from the good genes model?

a. Neither the good genes model nor the Fisher model predict a positive correlation between male ornamentation and male viability. b. The Fisher process operates on top of any good genes mechanism. c. Linkage disequilibrium between female preference and a male trait is predicted by both models. d. Neither model accounts for the effects of runaway sexual selection, which reinforces linkage disequilibrium.

During bacterial conjugation, small circular chromosomes of DNA, called plasmids, are transferred from one bacterial cell to another. Why does this mechanism NOT fit the common definition of sexual reproduction?

a. No new offspring are produced. b. No new allelic combinations are formed. c. The cell receiving the plasmid does not contain genetic material from both parents. d. The plasmid can recombine with the recipient cell's chromosome.

Would there be any disadvantage of sex if sexual reproduction was isogamous?

a. No; females would not pay the twofold cost of sex. b. Yes; sex may break up coadapted gene complexes. c. No; females would still transmit the same proportion of their genes to the next generation. d. Yes; isogamous parents contribute unequally to gamete production, resulting in one parent experiencing a greater cost of reproduction.

The figure shown illustrates the proportion of a particular asexual snail clone in a population and the degree to which it was infected with a particular parasite. Which prediction of the Red Queen hypothesis do these results appear to reflect?

oscillation in the relative frequency of asexual strains in the presence of parasites

For males, potential reproductive success is highest in a ________ mating system and lowest in a ________ mating system.

polygynous; polyandrous

12. Which of the following reproductive systems lends itself best to the study of the environmental factors that lead to the maintenance of sexual reproduction?

populations that respond to environmental changes with a change from asexual to sexual reproduction

Which step of the process of amphimixis produces new chromosomal variants?

recombination

Several studies have looked at the different reproductive behaviors of male bluegill fish Lepomis macrochirus, identifying different morphs that exhibit different strategies when attempting to fertilize eggs. Which morph displays male-male competition through cuckoldry and sperm competition?

sneaker

Some mammals have demonstrated preferential attraction to individuals that carry immune system alleles that are complementary to their own. Which hypothesis does this observation support?

the Red Queen hypothesis

What evolutionary model for the maintenance of sexual reproduction do the following data appear to support?

the Red Queen hypothesis

Morphological or behavioral characteristics used to attract a mate can also have the consequence of drawing a predator's attention to the individual who possesses that trait, yet these so-called expensive traits persist in many species. This describes

the handicap principle.

What do these data about the offspring of peacocks tell us about the good genes model of intersexual selection?

Chicks from fathers with feathers with large eyespots weighed more and had better rates of survival, indicating that tail length and ornamentation are indicators of male genetic quality.

Why is male reproductive success limited by the number of eggs?

Eggs are much larger and scarcer than sperm, limiting the number of opportunities for reproductive success for males.

What is the relationship between male quality and tail length in peacocks? Why do extravagant and metabolically costly traits like peacocks' tails persist in population?

Higher-quality males have higher fitness. The traits persist because females choose males with longer tail feathers; the more extravagant the tail is, the more often the male is chosen and the greater its fitness.

Describe the three-step process of amphimixis.

Recombination occurs as a result of crossover between homologous chromosomes; haploid gametes are produced by diploid individuals via meiosis; and after gametic exchange between individuals, haploid gametes fuse to produce a diploid offspring.

Which of the following statements describes an element of the Fisher-Muller hypothesis for adaptive advantage of sexual reproduction?

Sex facilitates the combination of favorable mutations that originated in different individuals into advantageous genotypes.

Explain how sexual reproduction overcomes the inherent disadvantage of generation time in the host of an asexually reproducing pathogen.

Sex provides a means to outcompete a pathogen by producing genetic variation, via recombination, that enables the host to overcome pathogens that evolved to evade the host immune response.

What did Curt Lively (1987) discover when applying the Red Queen hypothesis to snail populations in New Zealand?

Sexual reproduction was more common when the frequency of parasites was high, both in lakes and in streams.

Develop a short hypothetical explanation (one sentence) for the observed distribution of obligate asexual reproduction under the environmental unpredictability model.

The asexual species of this phylogeny appear to be fairly rare and short lived; therefore, it is likely they occupy very stable and predictable habitats, which favor sexual reproduction."

In a population that is polymorphic for sexual/asexual reproduction, a sexually transmitted disease has just eliminated most of the sexually reproducing individuals. When you expose samples of asexuals and sexuals from this population to harsh environmental conditions in the lab, you discover that the sexual individuals are worse at adapting to the new environment than the asexual individuals. (Note that your lab population is free from the sexually transmitted disease.) Which of the following statements is a likely explanation for your results?

The bottleneck caused by the disease resulted in the fixation of many alleles in the sexually reproducing population.

Counter the following argument: "Sexual reproduction is just an accident of evolution; once established it is irreversible. One does not need to postulate specific benefits to explain its maintenance."

There are recently evolved asexual lineages. Due to the various costs of sex, they would replace sexual populations if it weren't for the benefits of sexual reproduction that offset these costs.

What are two examples of asexual-like reproduction in the genomes of obligate sexually reproducing organisms?

Y chromosomes, mitochondrial DNA, chloroplasts, and other plastids.

Is it possible for a recombination event to turn Muller's ratchet "forward" in the population of chromosomes below? The dots on the chromosomes indicate deleterious mutations. Indicate the crossing-over event by placing an X on the figure.

Yes, by a crossing-over event between chromosomes C and D between the first and the second mutation of chromosome D.

In an experiment, Jokela and colleagues reared 14 replicate populations of a snail species that is polymorphic for sexual/asexual reproduction under controlled, identical conditions in the lab. Each population started with 35% asexual and 65% sexual individuals. The figure below shows the percentage of asexual individuals after a year-long experimental run. Which of the following statements is NOT a possible explanation for these results?

a. Asexual females survived better under the experimental conditions. b. Asexual females produced more offspring per individual than sexual females. c. Avoiding the cost of males allows faster population growth for the asexual subpopulation. d. A novel mutation after the start of the experiment led to the increased survival of the asexual line with the mutations.

Why is sexual reproduction believed to be the ancestral state in eukaryotes?

a. Asexual reproduction is completely absent from basal unicellular eukaryotes. b. Under the parsimony principle, the most common form of a trait's state is always the ancestral state. c. The "twiggy" distribution of obligate asexual reproduction in phylogenetic trees suggests that asexuality is a derived trait. d. Evolutionary models suggest that obligate asexual taxa are more prone to extinction than sexual ones.

What is the consequence of a deleterious mutation becoming fixed in a population?

a. Fixation of a deleterious mutation will automatically cause Muller's ratchet to move an additional turn. b. Recombination cannot remove the mutation. c. Mating between unrelated individuals can produce offspring that do not carry the mutation. d. Muller's ratchet can no longer turn.

Why are transduction, conjugation, and transformation sometimes referred to as sexual processes, but are not considered to be sexual reproduction?

a. Genetic material is exchanged, but the process does not involve meiosis and gamete fusion. b. Genetic material is exchanged, but exchange can take place between organisms of the same sex. c. Genetic material is not exchanged between two organisms; it is simply fused together into one new organism. d. Genetic material is divided in the process of meiosis, resulting in two haploid individuals without exchange of genetic material.

Why do some scientists consider automixis sexual reproduction?

a. It results in only heterozygous gametes. b. It allows for crossing-over and can turn back Muller's ratchet. c. Although the offspring are identical to their parents, it produces as much variation as sexual reproduction. d. It reshuffles variation that originated in a bisexually reproducing population.

Do each of the following forms of reproduction represent asexual or sexual reproduction? A. Amphimixis B. Automixis C. Apomixis

Amphimixis is a form of sexual reproduction; automixis and apomixis are forms of asexual reproduction.

You catalog all obligate asexual species within a family of insects and notice that asexual species are rare and are all members of genera that consist predominantly of sexual species. None of the genera consist exclusively of asexual species, and many of the asexual species have gone extinct. Your phylogenetic analysis shows that asexual species tend to be short "twigs" on the tree. What could you conclude from these results?

Asexual species tend to be short-lived taxa and go extinct more quickly than the sexually reproducing species.

Could HIV infection be considered a cost of sexual reproduction? Keep your answer to one sentence.

Because HIV is transmitted sexually, the risk of acquiring HIV is a cost of sexual reproduction in humans.

Why is the twofold cost of sex only seen in anisogamous organisms?

In anisogamous organisms, only females invest sufficient resources in gametes, allowing them to develop into adults. Males produce many small gametes but contribute essentially no biomass to the next generation. This results in the twofold cost of sex. In contrast, in isogamous organisms, both parents invest resources in gametes, meaning that two sexual isogamous parents produce as many offspring as two asexual parents, and do not pay the twofold cost of sex.

The two figures represent an asexual and a sexual population. The letters indicate beneficial mutations. The shaded areas represent the frequency of particular combinations of mutations in the population over time. Why does it take longer for the beneficial allele combination of ABC to go to fixation in the asexual population than in the sexual population?

In the asexual population, new allelic combinations have to arise via de novo mutations. In sexual mutations can arise easier bc of recombination

Under what conditions are asexual and sexual reproduction favored by the three evolutionary models shown in the figure, involving environmental unpredictability, number of niches, and parasite load? State whether a high or low value for each condition will favor sexual or asexual reproduction. A) Low environmental unpredictability B) High environmental unpredictability C) Low number of niches D) High number of niches E) Low parasite load F) High parasite load

Low values for each condition (A, C, and E) favor asexual reproduction and high values (B, D, and F) favor sexual reproduction.

How could the number of gametes produced relate to a reproductive success differential in males?

Males chosen by multiple females could have much higher reproductive success because of the large number of sperm produced by the male.

Does Muller's ratchet apply to both apomictic and automictic asexual populations?

No; Muller's ratchet does not apply to automictic asexuals, which can produce offspring with fewer deleterious mutations via recombination.

Why do pathogens tend to evolve faster than their hosts?

Pathogens tend to have much shorter generation times, and larger population sizes, than their hosts.

How does recombination in sexually reproducing organisms reverse the effect of Muller's ratchet?

Recombination can combine segments from each parent that have fewer deleterious mutations than were present in either parent's chromosome.

What are the two immediate benefits to sexual reproduction in unpredictable environments, according to Alexey Kondrashov?

Recombination may produce at least some variants that succeed in the changed environment, and genetic variation may reduce competition among offspring.

The Amazon molly, Poecillia formosa, is a freshwater fish that is gynogenetic. In order to reproduce, individuals of this all-female species must mate with a male from a closely related species to initiate the development of their offspring. The male's genetic material does not, however, enter the Amazon molly's egg. What costs of sexual reproduction does the Amazon molly potentially experience?

a. None; it reproduces asexually. b. It potentially experiences the costs associated with finding a mate and competing with other females for mates. c. The female may risk incorporating a deleterious gene from the male. d. It has no means of turning back Muller's ratchet.

11. Which of the following statements does NOT illustrate a potential cost of sexual reproduction?

a. Proteins in the seminal fluid of Drosophila males shorten the life expectancy of inseminated females. b. Female birds of paradise inspect several males before deciding with whom to mate. c. Male and female damselflies form characteristic mating wheels, which allow the partners to fly, albeit at slower speeds than single damselflies. d. Pronghorn males do not actively search for mates, reducing their gene flow throughout the population.

Water fleas, Daphnia magna, can switch between asexual and sexual reproduction cycles. Which of the following observations support the hypothesis that sex is favored in unpredictable environments?

a. The introduction of predators triggers sexual reproduction. b. D. magna reproduces asexually every other generation in a variety of habitats. c. D. magna reproduces sexually when in stable water conditions. d. Asexual D. magna strains outcompete introduced competitors.

Are there any costs when asexual organisms reproduce automictically as opposed to apomictically?

a. Yes; recombination may disrupt coadapted gene complexes. b. Yes; recombination is the cause of the twofold cost of sex. c. No; both are forms of asexual reproduction. d. No; recombination will produce more well-adapted individuals.

According to the reasoning of John Maynard Smith, in a mixed population of asexually reproducing females and sexually reproducing males and females, the number of asexuals should grow at twice the rate of the sexually reproducing individuals because

asexuals avoid the cost of producing males by producing offspring that do not need to be inseminated in order to reproduce, essentially only producing females.

In the crustacean genus Hyalella, females mate more often with males who have larger gnathopods. Males with larger gnathopods have been shown to be better protectors of females during amplexus. Which model of intersexual selection does this describe?

direct benefits

What are coadapted gene complexes?

favorable combinations of alleles at different loci

Birds of paradise are a family of tropical birds known for their striking sexual dimorphism. The males are famous for their elaborate, colorful plumage that combines with a variety of behaviors to attract females in their species for mating. Females choose the males based on their morphological and behavioral displays, providing an example of

intersexual selection.

What is the definition of "sexual reproduction"?

joining together of genetic material from two parents to produce an offspring with genes from each parent