Evolutionary Bio HW questions

The closest living relative of land plants is an aquatic green algae, but contradictory gene trees make it difficult to determine which green algae is the most closely related to the land plants

incomplete lineage sorting

There are more than 200 species of the iguanian genus of lizards Liolaemus. These lizards diversified rapidly, and many of the genes studied produce disparate gene trees. For this reason, scientists have had difficulty sorting out the evolutionary relationships in Liolaemus.

incomplete lineage sorting

Corals reproduce by releasing massive numbers of eggs and sperm into the water around them. Interbreeding is common in this mix of gametes from many species. Thus, a single species of coral can have alleles that are more commonly found in another species of coral.

introgression

Economically important crops, such as tomatoes and soybeans, tend to have low genetic diversity, which can make them susceptible disease and environmental stress. Scientists interbreed domesticated crop plants with their wild relatives to introduce genetic diversity and alleles that confer disease resistance and environmental stress tolerance

introgression

The Denisovans are a species of hominids that lived in Siberia and parts of Asia. A Denisovan allele has been found in people from the Himalayas that helps these humans adapt to the low oxygen concentrations at high altitudes.

introgression

What environmental condition did Rosemary and Peter Grant determine is responsible for forcing medium ground finches to become seed specialists on Daphne Major Island in the Galapagos Islands?

prolonged drought during the dry season

Some snowshoe hare populations have brown fur instead of white fur in winter. What evolutionary events do scientists believe led to winter‑brown fur in these populations?

1.) After the last Ice Age, climate change allowed for snow‑free winters, and natural selection favored the Agouti allele for winter‑brown fur. 2.) Introgression with black‑eared jackrabbits introduced an Agouti allele for winter‑brown fur into some snowshoe hare populations

Select the statements that describe molecular clocks.

1.) Fossils can allow scientist to calibrate mutation rates. 2.) Base-pair substitutions occur at a predictable rate. 3.) Different segments of DNA acquire mutations at different rates.

Select variables that lead to antagonistic coevolution between sexes in a species.

1.) The sexual strategy of one sex lowers the fitness of the other sex. 2.) A characteristic confers a fitness benefit to one sex and a fitness cost to the other.

What circumstance might give rise to a novel trait?

A deletion mutation alters the timing of the activation of a regulatory network.

Identify which species concept would be most appropriate for each scenario.

Suppose a paleontologist is studying dinosaur fossils from the Cretaceous period. Which species concept should the researcher use? -phylogenetic species concept Suppose an ecologist is studying the speciation of two groups of ground squirrels that live on either side of the Grand Canyon. Which species concept should the researcher use? -biological species concept Suppose a biologist is studying gene flow within metapopulations of triggerfish that live in the coral reefs of Thailand. Which species concept should the researcher use? -general lineage species concept

Identify whether each scenario describes a system of polyandry, polygyny, or monogamy

A male lion fights with other males to maintain breeding rights over a pride of females. -polygyny Black vultures share a pair‑bond and parental responsibilities that are reinforced by flock dynamics. -monogamy A female northern jacana defends a large territory in which her multiple mates each have a separate nest and incubate a clutch of her eggs. -polyandry

Predict how each situation would affect how quickly coalescence occurred? 1.) A beneficial allele experiences positive selection. 2.) A neutral allele exists sin a small population. 3.)A neutral allele exists in a large population. 4.)Two alleles exist that both have some posititve and some negative effects.

1.) Coalescence happens rapidly, occurring closer to the tips of the gene tree. 2.) Coalescence happens rapidly, occurring closer to the tips of the gene tree. 3.) Coalescence happens slowly, taking many generations. 4.) Coalescence happens slowly, taking many generations.

Select the reasons why sympatric speciation is difficult to find or document.

1.) Gene flow among diverging groups continues, despite some nonrandom mating. 2.) Diverging species occupy the same geographic location.

In the quest to understand the origin of modern humans, Homo sapiens, scientists have put forth opposing models. One of these, the Multiregional model, states that the first humans migrated out of Africa roughly two million years ago. Throughout the Old World, some gene flow allowed evolution as a single, continuous race, although populations evolved regional features. In contrast, the Out of Africa model states that modern humans evolved in Africa and only recently dispersed out of Africa. As Homo sapiens migrated through Eurasia, they replaced all other previously established hominid races and further evolved in genetic isolation. Which lines of evidence support the Out of Africa over the Multiregional model?

1.) Genetic analyses show that the majority of the genetic diversity of modern humans can be traced to africa. 2.) Outside of Africa, anatomically modern fossils are only frequent in recent times, whereas other hominid fossils are much older.

Select each statement that provides evidence that artificial selection has occurred

1.) Harvested wheat plants have traits that make them easier to gather than wild wheat plants. 2.) Livestock are less aggressive and more tolerant of penning than their wild counterparts. 3.) Kale, Brussels sprouts, cauliflower, and broccoli are the same species, Brassica oleracea

What characteristics of stickleback fish make them ideal for studying natural selection in the wild?

1.) Heritable variation in armor directly affects the fitness of sticklebacks. 2.) Stickleback populations are in environments with or without predators. 3.) Some stickleback populations are isolated in closed environments.

Select the statements that identify the importance of recognizing the presence of cryptic species.

1.) Policy makers can preserve cryptic species through legislation. 2.) Scientists can better classify biodiversity in ecosystems.

Identify reasons that scientists use 16S rRNA to identify microbial species.

1.) The 16S rRNA gene is well‑conserved among species. 2.) Parent cells pass the 16S rRNA gene to every daughter cell.

The cubic spline shown in the figure graphs Trait A, Trait B, and fitness. What conclusions can you draw based on this fitness curve?

1.) The highest fitness level occurs at relatively large values of both Traits A and B. 2.) A particular fitness level can be found at more than one combination of values for Traits A and B. 3.) Multiple peaks of fitness levels represent relatively favorable combinations of Traits A and B.

Select all the conditions that must be met for a trait to be described as an honest signal. The trait must

1.) be variable within the displaying sex and have a high cost to display. 2.) be heritable within the displaying sex and preferred by the opposite sex

For which purposes can scientists use molecular phylogenies?

1.) to identify adaptations for infection or transmission. 2.) to predict the evolution and emergence of new diseases. 3.) to trace the origin of pathogens among populations.

Select the statement that describes how a biased operational sex ratio (OSR) can generate strong sexual selection.

An OSR can create intense competition between members of the more abundant sex.

Classify each characteristic based on whether it describes the process of allopatric speciation, sympatric speciation, or both.

Allopatric speciation: -occurs through geographic isolation -caused by a physical barrier that prevents mating between subpopulations Sympatric speciation: -caused by gametic, behavioral, and temporal mechanisms -occurs among subpopulations that inhabit the same geographic area Both allopatric and sympatric speciation: -diverging subpopulations cannot successfully interbreed -caused by isolating barriers

Identify each description as a complex adaption or regulatory network.

Complex adaptation: a suite of coexpressed traits that together experience selection for a common function and a phenotype encoded and regulated by a complement of genetic and environmental elements. Regulatory network: a system of interacting genes, repressors, transcription factors, and RNA molecules and a biological circuit that responds to input signals with outputs that control the activation of genes.

Identify whether each scenario is an example of intersexual competition or intrasexual competition.

During the mating season, the greater sage grouse establishes leks. Leks are aggregations of males in which each male establishes a territory in visual or auditory range of other male territories. The males perform some display of their fitness, as females pass among the territories to choose a mate. What kind of sexual selection likely maintains lekking behavior? -intersexual selection When in rut, bull elk fight each other primarily by clashing antlers and trying to throw their opponents to the ground. The winner gains access to females in the harem until the next male challenges him. What kind of sexual selection likely maintains fighting behavior? -intrasexual selection Male dragonflies defend territories that have desirable resources for laying eggs from one another. Higher quality territories attract females and increase mating opportunities for males. What kind of sexual selection likely maintains territorial behavior? -intersexual selection

How are gene trees used to describe the history of a gene?

Gene trees show evolutionary relationships among the alleles of a gene within and between populations.

Determine whether each statement concerning female mate choice describes the good genes hypothesis, the Fisher's runaway hypothesis, or the Fisher-Zahavi hypothesis.

Good genes: Females choose mates by assessing a trait that directly reflects the genetic quality of the male, and their offspring's chances of reproducing increase because they inherited his genes Fisher's runaway: Females find an arbitrary male trait attractive and drive the evolution of increasingly extreme versions of the trait by producing sons with the attractive trait and daughters that prefer the trait Fisher-Zahavi: Females use an exaggerated trait that makes it harder for the male to survive as an honest indication of a potential mate's overall health and genetic quality, producing sons with the trait and daughters that prefer the trait

Snowshoe hares undergo seasonal molting. Individuals in most populations molt from brown to white in the fall. Some individuals molt from brown to brown in the fall. Scientists have found that the color polymorphism tracks a winter climate gradient. What is the likely effect that a warming climate will have on the distribution of phenotypes?

Hares with winter-brown phenotype will expand into increasingly higher latitudes.

Populations of oldfield mice living on white sand beaches have light‑colored fur. Populations living on darker inland soils have darker fur, although a range of lighter fur colors can occur. Sequence the events that produced the light‑furred beach populations from the darker‑furred inland populations.

Inland populations of mice with dark fur 1. some mice spread into habitats on the white sand beaches. 2. predators ate more dark-furred mice than mice with lighter fur. 3. alleles for light fur steadily increased in frequency in the population, Beach population of mice with light fur

Why does sexual monogamy tend to reduce sexual conflict?

It benefits the fitness of both the male and female to not thwart or harm each other because they have only one partner for mating.

Each example describes a barrier that keeps a pair of species separated in the wild. Identify whether each barrier is an allopatric or reproductive barrier.

Lions and tigers live on different continents. In zoos, they can breed and produce ligers and tigons. Is this an example of an allopatric or reproductive barrier? -Allopatric Kaibab squirrels occupy the north rim of the Grand Canyon while Abert squirrels live on the south rim of the Grand Canyon. Is this an example of an allopatric or reproductive barrier? -Allopatic The males of different firefly species flash unique patterns to attract females. The females are only attracted to particular light sequences. Is this an example of an allopatric or reproductive barrier? -reproductive The red‑legged frog and bullfrog both live in aquatic habitats in California. However, red‑legged frogs prefer to perform courtship rituals in streams, whereas bullfrogs prefer to perform courtship rituals in ponds. Is this an example of an allopatric or reproductive barrier? -reproductive

How does anisogamy influence mating strategies?

Males fight for access to females to secure mating opportunities.

Arrange the steps of natural selection to describe the evolution of armor among stickleback fish in freshwater lakes.

Marine stickleback fish had heavy armor. 1.) A mutation in the Eda gene gave rise to the low‑Eda allele, resulting in variation in armor plating. 2.) Marine sticklebacks carrying the recessive low‑armor Eda mutation spread into freshwater habitats 3.) Some freshwater environments became closed systems of lakes with few or no predators 4.) In freshwater lakes, sticklebacks with less armor produced more offspring than sticklebacks with more armor Most stickleback populations in lakes evolved a predominance of light armor.

Sort the characteristics of maximum likelihood and Bayesian methods of analysis.

Maximum likelihood methods: determines the probability that a data set can be reconstructed. Bayesian methods: determines the probability that a hypothetical tree is correct. Both maximum likelihood and Bayesian methods: analysis begins with a priori evolutionary model and is used to evaluate phylogenies

Which of the following is an example of a Bateson-Dobzhansky-Muller incompatibility?

Mules are the hybrid offspring of horses and donkeys and almost always exhibit hybrid sterility.

Sort the scenarios according to whether the mutations would spread by natural selection, neutral evolution, or both.

Natural selection: A mutation in a protein-coding gene changes the amino acid sequence of a protein. And. A mutation in a pseudogene changes the transcription rate of a protein. Neutral evolution: A mutation in a pseudogene produces no downstream consequences and a mutation in a protein-coding gene does not change the amino acid sequence of a protein. Both: A mutation in a protein-coding gene becomes fixed in a population.

What is the most likely explanation for all extant copies of a gene coalescing?

One gene copy out of the multitude of copies that existed in the past gave rise to all the extant copies.

Identify the key components, inherent assumptions, and drawbacks for the three major species concepts.

Phylogenetic species concept: -defines species by morphological characteristics -defines species as a group that possesses distinguishing characteristics from other groups -does not work well if there is high morphological variation in a species Biological species concept: -only applies to species that reproduce sexually -requires interbreeding individuals General lineage species concept: -defines species as a metapopulation that exchanges alleles and shares an evolutionary lineage -may group morphologically different populations as the same species

Classify statements according to whether they describe polygyny, polyandry, or monogamy.

Polygyny: A male can sire a higher number of offspring than other males. A male has a higher probability of injury during competitive jousts. Polyandry: A female increases genetic variability and quality among her offspring. A female acquires extra resources through nuptial gifts. A female has a higher probability of injury during competitive jousts. Monogamy: A male raises the probability that offspring from a given female are his. A male increases his fitness by helping to raise young. Genetic variation among offspring is low.

How is the neutral theory of evolution used to deduce the timing of evolutionary events and the history of natural selection?

Scientists use a steady rate of mutation accumulation to date events and apply the theory as a null hypothesis for natural selection.

What is the most likely explanation for why mice on both the Atlantic Coast and Gulf Coast of Florida have lighter fur than mainland mice?

Selection pressures on coat color are similar on both coasts.

Identify whether hybridization would likely lead to speciation or homogenization in each scenario.

Several breeding pairs of cactus finch—ground finch hybrids have successfully produced fertile, viable offspring for at least three consecutive generations. These hybrids have been unsuccessful breeding to non‑hybrid cactus finches or ground finches. Are the hybrid finches likely to be speciating or homogenizing? -speciation The Texas bluebonnet, a flower native to Texas, grows wild along roadsides. It is also planted along roadsides in many beautification projects across Texas. Breeding between the planted bluebonnets and wild bluebonnets produces a hybrid that is genetically compatible with both parental varieties. Are the hyrbid bluebonnets likely to be speciating or homogenizing? -homogenization Helianthus anomalus is a hybrid sunflower created by the natural breeding of H. annuus and H. petiolarus. Helianthus anomalus is a fertile, viable hybrid that can only successfully reproduce with other H. anaomalus. Are the hybrid sunflowers likely to be speciating or homogenizing? -speciation

Why did early studies of ape phylogeny that were based on single gene analysis produce confusing results?

Some of the genes used in the studies experienced incomplete lineage sorting.

Classify each graph, image, and scenario as describing stabilizing or directional selection.

Stabilizing selection: unequal peak heights, medium is favored phenotype. "For a gallfly, predation by one predator is greatest on the largest galls, and predation by a different predator is greatest on the smallest galls." Directional selection: equal peak heights, extreme phenotype is selected. "In a population of sockeye salmon, late‑season predation pressure over multiple generations causes a shift to an increasingly earlier migration date."

In which situation is sexual conflict most likely to result in the evolution of a new species?

Strategies used against the opposite sex to increase individual fitness continuously evolve in two geographically separate populations.

In each scenario, how would phenotypic change in a species likely affect antagonistic coevolution between the sexes?

Suppose a pleiotropic mutation occurs in some females of a duck species. The mutation results in fewer coils and pouches in the oviduct and a higher quality eggshell. -Antagonistic coevolution decreases. Suppose the average tail length in males of a showy bird species is increasing over time. The females of the species tend to choose mates with longer tails. -Antagonistic coevolution does not change. Suppose there is an increase in the frequency of an allele in female fruit flies. The allele codes for a protein that neutralizes the toxic chemicals that males deposit in the female reproductive tract during mating. -Antagonistic coevolution increases.

Use the description of each species' life history to identify the factor likeliest to affect female mate choice.

The common whitetail dragonfly, Libellula lydia, is frequent throughout North America. The males have a characteristic white powder that covers a pale blue abdomen, and adult females have a brown abdomen with white hatch marks. Males establish and defend territories over pools of water. Females release fertilized eggs by dipping their abdomens in the water. When the eggs hatch, nymphs live and grow in the water for months or years. Once they reach a minimum size, they crawl onto land to morph into their adult forms. It takes them about two weeks to grow to full size, and they then return to a body of water to mate. Which factor is likeliest to affect female mate choice in the common whitetail dragonfly? -quality of the male's territory The wild turkey, Meleagris gallopavo, forms winter flocks made of family groups of either female hens and young poults or male gobblers. Gobblers have exaggerated characteristics that set them apart from the females, including a waddle, snood, and large tail. Gobblers that have a smaller parasite load have a larger snood and larger skullcap. During the breeding season, gobblers perform an elaborate dance around hens to entice them to mate. Once mated, females build secret nests in dense vegetation in which to lay and hatch their eggs. Which factor is likeliest to affect female mate choice in the wild turkey? -size of a male's snood and skullcap The penduline tit, Remiz pendulinus, is a small passerine bird. Both sexes have similar coloration, including a black mask around the eyes, though males have larger masks than females. Both sexes are sequentially polygamous, meaning that a single parent stays with a nest to incubate and raise the young. The birds are named for the hanging nests they build. Males build nests that differ in size, and they sing to attract females. Larger nests can accommodate a greater number of young. The probability that a male abandons a nest is not related to nest size. Which factor is likeliest to affect female mate choice in the penduline tit? -size of the male's nest

Determine whether each scenario describes an extended phenotype.

The gall is an extended phenotype: True Coat color is an extended phenotype of the hare: False The case is an extended phenotype of the caddisfly: True The cricket's behavior is an extended phenotype of the worm: True

Suppose that scientists are investigating populations of a species of phlox to determine if the they are evolving different adaptations to their local environments. They investigate multiple segments of DNA to identify locations of synonymous (d/S ) and non‑synonymous (d/N ) mutations. For each scenario, determine whether scientists should accept or reject the null hypothesis of neutral evolution.

The light environment for each population differs. The scientists analyze a gene related to stem structure and find that the frequency of non‑synonymous mutations is much less than the frequency of synonymous mutations. -reject null hypothesis of neutral evolution Each population has a different frequency of asters with blue or purple flower petals. Scientists investigate a gene for petal color and find that the frequency of non‑synonymous mutations is nearly the same as the frequency of synonymous mutations. -accept null hypothesis of neutral evolution The populations are in fields with different hydrology. The scientists analyze a gene related to root structure and determine that the frequency of non‑synonymous mutations is much greater than the frequency of synonymous mutations. -reject null hypothesis of neutral evolution This data suggest that which traits are under selection? Root structure and stem structure