BIO 212 Test 1

CAREFULLY How can evolutionary fitness be measured? Select True or False for each statement. T/F Count the number of healthy, fertile offspring produced.

True

Apply Darwin's four postulates to a population of mice living on sand dunes in coastal Florida.

(1) Fur color varies within mouse populations. (2) Fur color is heritable. (3) More mice are produced than can survive, and some produce many surviving offspring while others produce few or none. (4) Mice with certain heritable traits, such as the ability to avoid predators by blending in their environment (camouflage), survive and produce more offspring.

In a population of 2500, how many babies would you expect to have cystic fibrosis, a homozygous recessive condition, if the frequency of the dominant allele is 0.9 and the population is at Hardy-Weinberg equilibrium?

0.1 * 0.1 * 2500 = 25

if one species (2n = 10) crosses with another species (2n = 18), producing an allopolyploid offspring, what is the ploidy of the offspring?

2n = 10 + 18 = 28

Which of the following describes vicariance?

A population is fragmented into isolated subpopulations.

Toucans can eat fruits with large seeds because their large bills can open wide. Most other birds in the same forest can only eat small seeds. Ecologist Mauro Galetti and his colleagues measured the seed sizes of palms in forest fragments with and without toucans. The graphs show two of the forest populations they studied. What is the take-home message of the data?

Average seed size is lower in the forest fragment with toucans absent (about 9.5 mm) than in the forest with toucans present (about 11 mm).

Human populations today are not considered separate species under the biological species, morphospecies, and phylogenetic concepts. Explain what kind of evidence supports this statement.

Biological species concept: Human populations are not considered separate species because all human populations can successfully interbreed. Morphological species concept: Although people of different races and from different populations look superficially different, they are not separate species because they have virtually identical anatomy and physiology. Phylogenetic species concept: Human populations are not separate species because they all arose from a very recent common ancestor and cluster together as one branch in a phylogenetic tree of species. (DNA comparisons have revealed that human races are remarkably similar genetically and do not differ enough to qualify for species status.)

When a statistical test was used to compare the results for white models versus brown models, the P value (see BioSkills 3) was 0.01 for each habitat. Does this result increase or decrease your confidence in your take-home message? Explain.

Biologists consider a P value less than 0.05 to be statistically significant, that is, showing a real difference and not just sampling error. Since 0.01 < 0.05, you can be confident that the mice that were camouflaged were attacked less than those that were not.

Do these data illustrate directional, stabilizing, disruptive, or balancing selection? Justify your answer in terms of fitness.

Directional selection. The average seed size of palms has declined in the absence of toucans, presumably because smaller seeds have higher fitness in the absence of toucans.

Compare how evolution by inheritance of acquired characters and the theory of evolution by natural selection would explain the observation of white mice living primarily on light soil and brown mice living primarily on dark soil.

Evolution by inheritance of acquired characteristics predicts that the mice in the different environments needed to change color, so they did so and then passed their traits on to their offspring. The theory of evolution by natural selection is not goal oriented. It predicts that white and brown mice are descendants of an ancestral population that varied in color. The white mice had higher fitness in the sand dunes environment, where they were more likely to escape the notice of predators. Likewise, the brown mice had higher fitness in the mainland environment.

Neanderthals disappeared about 40,000 years ago when the modern human population increased. This is an example of what outcome(s) of secondary contact (see Table 24.4)? Predict one way this result might have come about.

Extinction of one population. Modern humans may have been stronger competitors (better able to obtain food or other resources), which likely contributed to the Neanderthals' extinction.

According to data presented in this chapter, which of the following are correct? Select True or False for each statement. T/F Species are created independently of each other and do not change over time.

False

According to data presented in this chapter, which of the following are correct? Select True or False for each statement. T/F The traits of populations become more perfect over time.

False

According to data presented in this chapter, which of the following are correct? Select True or False for each statement. T/F When individuals change in response to challenges from the environment, their altered traits are passed on to offspring.

False

CAREFULLY How can evolutionary fitness be measured? Select True or False for each statement. T/F Determine which individuals are strongest.

False

CAREFULLY How can evolutionary fitness be measured? Select True or False for each statement. T/F Determine which phenotype is the most common.

False

CAREFULLY How can evolutionary fitness be measured? Select True or False for each statement. T/F Document how long individuals survive.

False

Select True or False to indicate which of the following groups could be identified using the biological species concept. T/F bacteria living today

False

Select True or False to indicate which of the following groups could be identified using the biological species concept. T/F extinct dinosaurs

False

True or false? Some traits are considered vestigial because they existed long ago.

False

Why does the presence of extinct forms and transitional features in the fossil record support the pattern component of the theory of evolution by natural selection? Select True or False for each statement. T/F It supports the hypothesis that individuals change over time.

False

Why does the presence of extinct forms and transitional features in the fossil record support the pattern component of the theory of evolution by natural selection? Select True or False for each statement. T/F It supports the hypothesis that species evolve to become more complex and better adapted over time.

False

Why does the presence of extinct forms and transitional features in the fossil record support the pattern component of the theory of evolution by natural selection? Select True or False for each statement. T/F It supports the hypothesis that weaker species are eliminated by natural selection.

False

Why is genetic drift aptly named? Select True or False for each statement. T/F It occurs when alleles from one population drift into another.

False

Why is genetic drift aptly named? Select True or False for each statement. T/F It occurs when mutations drift into a genome.

False

True or false? Speciation is a slow process. Justify your answer.

False. Speciation is sometimes a slow process, as in the formation of 8 species of trumpeters over 3 million years. But speciation can occur rapidly, as in the formation of a new species of Tragopogon by allopolyploidy in a single generation. Freeman, Scott. Biological Science (p. A:30). Pearson Education. Kindle Edition.

Suppose you were studying several species of monkeys. In one, males never helped females raise offspring. In another, males provided just as much parental care as females except for actually carrying the fetus during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?

For the species whose males never help raise offspring, the fundamental asymmetry of sex is pronounced, and sexual dimorphism is likely to be high. If males invest a great deal in raising offspring, then the fundamental asymmetry of sex is small and sexual dimorphism is likely to be low.

The data in the graphs are from two of the 22 forest fragments studied by the researchers: 7 with toucans present, 15 with toucans absent. Why do you think the researchers bothered to study so many forest fragments?

Forest fragments may vary in slope, moisture, species composition, and other factors. If the researchers compare just two fragments, they may happen to get a result that is not typical of the other fragments, by chance. By comparing many fragments, the researchers can be more confident that the trend in their samples represents a real trend in the rest of the forest.

Traits that are derived from a common ancestor, like the bones of human arms and bird wings, are said to be ________.

Homologous

Coral reefs are biodiverse ecosystems that provide food, income, coastal protection, and many other services to millions of people. Yet coral reefs are under threat from human impacts such as climate change—many corals cannot tolerate the warming ocean water and have suffered massive "bleaching" events, which can be fatal. Researchers have discovered that some corals have the capacity to acclimatize to warmer water, while other corals do not. The researchers fear that because corals are long-lived colonial animals and thus evolve slowly, they may not be able to adapt to global warming fast enough to avoid extinction. Explain how the difference between acclimatize and adapt is important to the fate of corals.

If an individual coral colony can acclimatize to the warming water, this means it might survive as the ocean continues to warm. Individuals that cannot acclimatize will die. Over time, natural selection will favor corals that have heritable characteristics that enable them to tolerate warm water. That is, coral populations will adapt to warm water (as long as the rate of warming does not surpass the temperature tolerance of all corals, which are not able to disperse rapidly to new habitats).

Large seeds carry more resources than small seeds and tend to have a higher rate of survival, especially after being dispersed by a bird. Predict how the local extinction of toucans will affect the palm population over time.

If larger palm seeds have higher fitness than smaller palm seeds (in the presence of toucans), then the fitness of palms will decrease over time in the absence of toucans because the large seeds will no longer be dispersed and will have a lower chance of survival.

All over the world, natural habitats are being fragmented into tiny islands by suburbs, ranches, farms, and roads. If asked to join a science panel to speak to Congress, could you explain how this fragmentation process could lead to extinction? How it could lead to speciation?

If the isolated populations and habitat fragments are small enough, species are likely to dwindle to extinction due to inbreeding and loss of genetic variation, or due to catastrophes such as a severe storm or a disease outbreak. If the isolated populations survive, they are likely to diverge into new species via allopatric speciation due to these vicariance events, because they are genetically isolated and because the habitats may differ.

In humans, albinism is caused by loss-of-function mutations in genes involved in the synthesis of melanin, the dark pigment in skin. Only people homozygous for a loss-of-function allele (genotype aa) have the albino phenotype. In Americans of northern European ancestry, albino individuals are present at a frequency of about 1 in 10,000 (or 0.0001). Assuming that genotypes are in Hardy-Weinberg equilibrium, what is the predicted frequency of Caucasians in the United States who carry a single allele for albinism?

If we let q stand for the frequency of the loss-offunction allele, we know that q2 = 0.0001; therefore q = 20.0001 = 0.01. By subtraction, the frequencyof normal alleles is 0.99. Under the Hardy-Weinberg principle, the frequency of heterozygotes is 2pq, or 2 * 0.99 * 0.01, which is 0.02 (about 2 people per hundred).

Why don't the biggest and strongest individuals in a population always produce the most offspring?

In some environments, being big and strong lowers fitness.

In what sense is the Hardy-Weinberg principle a null hypothesis?

It defines what genotype and allele frequencies are expected if evolutionary processes and nonrandom mating are not occurring.

Why isn't inbreeding considered an evolutionary process?

It does not change allele frequencies.

What distinguishes a morphospecies?

It has distinctive characteristics, such as size, shape, or coloration.

According to data presented in this chapter, which of the following are correct? Select True or False for each statement. T/F Populations—not individuals—change when natural selection occurs.

True

In the 1700s and 1800s, royalty in Europe often married their close relatives; furthermore, recessive genetic diseases such as hemophilia showed up much more often among royals than in the general population. Explain the likely connection.

Marrying close relatives is a form of inbreeding that would have increased the homozygosity of recessive alleles (inbreeding tends to shift alleles from heterozygotes, where they don't cause disease, to homozygotes, where they do). As a result, the royal families were plagued by genetic diseases.

Some biologists summarize evolution by natural selection with the phrase "mutation proposes, selection disposes." Mutation is a process that creates heritable variation. Explain what the phrase means.

Mutation produces new genetic variations, at random, with no forethought about which variations might prove adaptive in the future. Individuals with mutations that are disadvantageous won't produce many offspring, but individuals with beneficial mutations will produce many offspring. The beneficial mutations will thus increase in frequency through selection.

Determine what is incorrect in the following statement: Red deer mutated their genes so that they could have larger antlers to compete for mates.

Mutations do not occur because an organism wants or needs them. They just happen by accident and can be beneficial, neutral, or deleterious.

A team led by evolutionary biologist Hopi Hoekstra set out to test the hypothesis that predators are an agent of natural selection on mouse color. They made 250 plasticine models of mice that were alike in every way except that half were painted white and half were painted brown. Suggest one advantage and one disadvantage of using model mice instead of real mice in this experiment.

One advantage of models is that all the mice are exactly alike except for color, enabling the control of all variables except the one being studied. Models are also easier to work with than live mice. One disadvantage of using models is that they do not have the same smell and behaviors as real mice.

The researchers placed white and brown mouse models both in abandoned fields on the mainland (dark soil) and on sand dunes on the islands (light soil) and then measured the percentage of models that were attacked by predators. What is the take-home message of the data? Do the data support or reject the hypothesis that mouse color is adaptive?

The data show that mice that do not match the color of the soil are attacked more often than mice that do match. This supports the hypothesis that fur color is an adaptation in mice, because mice that avoid detection by predators are more likely to survive and produce offspring.

Before the application of DNA sequencing to fossils, which species concept was most useful for distinguishing human fossils? What is one disadvantage of this approach?

The morphospecies concept was used to distinguish fossil species. It was very difficult to determine whether morphological differences among fossils represented normal variation within populations (e.g., difference between a male and female) or meaningful differences among species.

Evaluate this statement: Gene flow increases the genetic divergence of populations.

The statement is false; gene flow reduces the divergence of populations.

Three-spine sticklebacks are small fish that originated in the ocean and continue to exist there, but then some took up residence in hundreds of streams and freshwater lakes in the Northern Hemisphere. Predict whether you would expect to find different species in lakes today.

The sticklebacks are geographically isolated in the different lakes. This is a classic setting for allopatric speciation to occur. Whether the fish in the different lakes would be considered different species today depends on how much time has passed since the populations diverged and which species concept is used.

The geneticist James Crow wrote that successful scientific theories have the following characteristics: (1) They explain otherwise puzzling observations; (2) they provide connections between otherwise disparate observations; (3) they make predictions that can be tested; and (4) they are heuristic, meaning that they open up new avenues of theory and experimentation. Crow added two other elements of scientific theories that he considered important on a personal, emotional level: (5) They should be elegant, in the sense of being simple and powerful; and (6) they should have an element of surprise. How well does the theory of evolution by natural selection fulfill these six criteria?

The theory of evolution fits the six criteria as follows. (1) and (2) It provides a common underlying mechanism responsible for puzzling observations such as homology, geographic proximity of similar species, the law of succession in the fossil record, vestigial traits, and extinctions. (3) and (4) It suggests new lines of research to test predictions about the outcome of changing environmental conditions in populations, about the presence of transitional forms in the fossil record, and so on. (5) It is a simple idea that explains the tremendous diversity of living and fossil organisms and why species continue to change today. (6) The realization that all organisms are related by common descent and that none are higher or lower than others was a surprise.

If you were a journalist covering this story, how could you use data from this study to respond to the following social media post? "Evolution is a slow process. Humans do not cause evolution in other organisms."

This statement is false. You could point out that the data show clearly that evolution in palm seed size has occurred over the few decades since humans have caused forest fragmentation and local extinction of toucans. Evolution, a change in allele frequencies in a population, can occur as quickly as in a single generation. In this case, human fragmentation of the forest has already caused measurable evolution in the forest—and this effect is likely to increase over time as the fitness of the palms declines, causing a cascade of effects on other species.

If you sequenced the DNA of all your classmates, you would probably observe that the percentage of Neanderthal genes in their genomes varies from 0-4%. How would you know whether there is a significant difference in percentage between students with blue eyes and students with brown eyes (see BioSkills 3)?

To determine if there is a significant difference between groups, you could separate the data by eye color then run a statistical test such as a T-test (BioSkills 3) to compare the means and variance of the two groups. If P 6 0.05 the difference is said to be significant.

Select True or False to indicate which of the following groups could be identified using the biological species concept. T/F lizard species living today

True

Select True or False to indicate which of the following groups could be identified using the biological species concept. T/F sunflower species living today

True

Why does the presence of extinct forms and transitional features in the fossil record support the pattern component of the theory of evolution by natural selection? Select True or False for each statement. T/F It supports the hypothesis that species change over time.

True

Why is genetic drift aptly named? Select True or False for each statement. T/F It causes allele frequencies to drift up or down randomly.

True

True or false? Gene flow can either increase or decrease the average fitness of a population. Explain.

True. If gene flow into a population introduces a beneficial allele, fitness will go up; but if gene flow introduces a deleterious allele, fitness will go down.

When the ranges of two different species meet, a stable "hybrid zone" occupied by hybrid individuals may form. How is this possible?

Two diverged populations are capable of mating and producing viable and fertile offspring.

Sexual selection favors individuals with traits that increase their ability to obtain mates, such as mating calls in crickets. Using this example, propose a scenario where sexual selection could contribute to divergence in sympatric speciation.

Variation in male calls could occur, such as a lower-pitched call at the cool forest floor and a higher-pitched call in the warm forest canopy. Females in the forest floor could start to prefer males with lower-pitched calls, and females in the canopy could start to prefer males with higher-pitched calls, creating genetic isolation. Over time, genetic divergence could occur between the two populations.

Explain why the overprescription of antibiotics by doctors, or the overuse of everyday soaps containing antibiotics, can be a health risk.

When antibiotics are overused, susceptible bacteria are constantly being killed off, even when an infection is not present. However, any individual bacteria that are resistant to these antibiotics will survive and multiply, reducing the likelihood that antibiotic treatment will be effective in the future.

Svante Pääbo and colleagues were the first to sequence the Neanderthal genome from fossils and compare the sequences to modern humans. According to the data shown here, did the two species interbreed when they overlapped in Europe? Explain. .

Yes. Modern humans and Neanderthals interbred in Europe after modern humans migrated out of Africa. This explains why modern Africans have no Neanderthal genes, but many humans in other parts of the world do carry Neanderthal genes—they are the result of hybridization events between the two species.

Draw a small concept map (BioSkills 12) showing how selection, genetic drift, gene flow, and mutation relate to genetic variation.

Your concept map should have linking verbs that relate the following information: Selection may decrease, maintain, or increase genetic variation. Genetic drift tends to reduce it by causing random loss or fixation of alleles. Gene flow may increase or decrease variation.

What is an evolutionary adaptation?

a trait that improves the fitness of its bearer, compared with individuals without the trait

Toucans disperse seeds of key forest species such as juçara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. If there are no toucans, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why?

decrease (due to decreased gene flow)

Modern humans (Homo sapiens) and archaic humans called Neanderthals (H. neanderthalensis) shared a common ancestor in Africa but diverged in different geographic areas. When modern humans migrated out of Africa and dispersed around the world starting about 100,000 years ago, they overlapped with Neanderthals in Europe. This scenario is best described as

species living in sympatry following allopatric speciation