Mastering Biology Monkey Flowers Question

2017/3/30Chapter 22 ­ Descent With modification HW

Chapter 22 ­ Descent With modification HW

Due: 11:59pm on Friday, January 20, 2017

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Scientific Thinking: What Clues About Biology Might Road Kill Provide?

Have you ever driven under a highway overpass or on a bridge and noticed a colony of cliff swallows like the one shown here?

Although this might seem like an odd place for birds to nest, it turns out it’s not. The edges between the horizontal overpass and vertical walls are actually ideal locations for swallows to build their mud nests. Unfortunately, however, these nesting sites also make cliff swallows vulnerable to being hit by cars and trucks.

In this activity, you will explore some observations that scientists made while studying cliff swallow nesting sites and deaths on Nebraska’s roads. You’ll also analyze the data they collected, which led them to ask many interesting questions about causes, adaptations, and natural selection.

© Charles R. Brown

Part A ­ Developing hypotheses

A group of researchers gathered data on the number of cliff swallow road kills they observed while driving between nest sites in Nebraska. The data cover a period of about 30 years and date back to the time when cliff swallows first started to nest under highway overpasses.

As the graph shows, the number of road kills observed declined sharply over time. The data led the researchers to ask themselves this question: What caused this decline?

Data from C. R. Brown and M. B. Brown. Where has all the road kill gone? Current Biology 23: R233­R234 (2013).

Which of the following are testable hypotheses that could explain the researchers’ data? Select all that apply.

ANSWER:

Traits that help individuals avoid being hit by cars have evolved through natural selection in the cliff swallow population.

An unknown element has been protecting the swallows.

The number of cars driving on these roads has increased over time.

The population size of cliff swallows living near roads has decreased over time.

Scavenger population sizes have increased, and more road­killed swallows get eaten before they can be found.

Correct

Researchers came up with numerous hypotheses that could explain why fewer cliff swallows were being killed on roads. Their hypotheses included the following:

Traits that help individuals avoid being hit by cars have evolved through natural selection in the cliff swallow population.

The population size of cliff swallows living near roads has decreased over time.

Scavenger population sizes have increased, and more road­killed swallows get eaten before they can be found.

The number of cars driving on these roads has decreased over time.

Part B ­ Testing hypotheses

To test their hypotheses, the researchers examined the data they collected during the period of study.

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2017/3/30Chapter 22 ­ Descent With modification HW

Using the information available to them, they assessed whether the population sizes of cliff swallows and potential scavengers living near highways had changed over time.

They determined how traffic patterns on these roads had changed over time.

They also measured the bodies of cliff swallows that had been killed on the roads and compared their features to the features of cliff swallows in the general population.

The table below summarizes the researchers’ findings.

Drag the blue labels onto the table to identify the data that is relevant to each hypothesis. Then use the pink labels to indicate whether each hypothesis is supported or not supported by the data.

ANSWER:

Correct

The researchers’ data suggest that one of the hypotheses may be supported ­­ traits that help individuals avoid being hit by cars may have evolved through natural selection in the cliff swallow population. Specifically, a different wing shape may make some swallows less vulnerable to being killed by cars.

Part C ­ Interpreting data

The researchers decided to take a closer look at the data they had collected on the shape and length of the cliff swallows’ wings.

This graph compares the wing length data collected from cliff swallows that were killed on the roads (blue bars) and from cliff swallows in the general population (maroon bars).

Analyze the data in the graph and use it to complete the sentences below.

Data from C. R. Brown and M. B. Brown. Where has all the road kill gone? Current Biology 23: R233­R234 (2013).

Drag the terms on the left to the appropriate blanks on the right

to complete the sentences. Not all terms will be used.

ANSWER:

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2017/3/30

produced by new mutations

gene flow

Chapter 22 ­ Descent With modification HW

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1. From 1984 to 2012, the wing length of cliff swallows in the general population generally decreased .

2. During the same time period, the wing length of cliff swallows killed on the roads generally increased .

3. In most years where data was collected, the wings of cliff swallows killed on the roads were longer than the wings of swallows found in the population at large.

Shorter wings allow cliff swallows to take off from the ground more vertically, enabling them to better avoid oncoming cars. As a result, cliff swallows in populations near highways with shorter

wings have a survival advantage.

The data suggest that, over time, natural selection resulted in the evolution of shorter wings in the cliff swallow population.

Shorter wings are a(n) adaptation in this population. Alleles for shorter wings were

already present in the general population.

Correct

The data collected by researchers suggest that shorter wing lengths have evolved over time in cliff swallow populations living near highways. Natural selection favors shorter wings, which allow the birds to take off from the ground more vertically and enable them to better avoid oncoming cars. This adaptation likely explains why so many fewer cliff swallows are found as road kill now than 30 years ago, when cliff swallows first started nesting under overpasses.

However, other factors may also have contributed to shorter wing length in cliff swallows. For example, changes in insect prey and severe weather events may also have resulted in selection on wing length. These factors need further exploration.

Evidence for Evolution

Charles Darwin described evolution as “descent with modification,” meaning that species change through time. A great deal of evidence indicates that life has evolved over time and continues to evolve. Natural selection is the primary mechanism by which evolution takes place.

Part A ­ Scientific evidence supporting evolution

Scientific evidence documents the pattern of evolution. The evidence exists in a variety of categories, including direct observation of evolutionary change, the fossil record, homology, and biogeography. Sort the following examples into the correct categories.

Drag each phrase to the appropriate bin.

Hint 1. What are the meanings of the terms relating to evidence for evolution?

Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.

ANSWER:

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1. The term homology refers to a similarity in a characteristic (such as DNA sequences, body parts, or development) that results from common ancestry.

2. A(n) vestigial structure is a remnant feature that has lost most or all of its original function and is similar to functional features in related species.

3. The fossil record provides data about transitional forms of some organisms.

The direct observation of living species as they change provides some of the evidence for evolution.

5. Biogeography refers to the distribution of species on Earth.

A(n) endemic species is an organism that is found in a specific area but does not exist naturally anywhere else in the world.

Hint 2. Skeletal structure of mammalian forelimbs

The forelimbs of mammals, regardless of shape or function, have the same arrangement of bones. The most parsimonious explanation (the one that is least complex and requires the fewest evolutionary changes) is that the different forelimbs represent variations of a structure present in a common ancestor. The image below shows the forelimbs of four mammals: human, cat, whale, and bat.

Similar characteristics in different species that result from having a common ancestor are called homologies.

Hint 3. Transitional forms and extinct species

The fossil record shows that present­day organisms differ from past organisms and that many species have become extinct. In addition, fossils can document evolutionary changes that have occurred in particular groups of organisms through time. For example, the following diagram shows part of the fossil record of horses. Notice that the large present­day horse (Equus), which has a single toe on each foot and teeth adapted for grazing, evolved from a small, many­toed ancestor (Hyracotherium) with teeth adapted for browsing. With the exception of Equus, all of the organisms shown in the diagram are extinct.

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ANSWER:

similarities in

mammalian forelimbs

discovery of shells

of extinct species

discovery of transitional

forms of horses

same genetic code in

fireflies and tobacco plants

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the high concentration of

marsupial species

in Australia

similarity of endemic

island species to

nearby mainland species

Correct

Scientists have directly observed evolution occurring in many instances, including the development of drug resistance in bacteria and other pathogens. The fossil record has provided evidence for extinct species and for transitional forms of organisms, such as the ancestors of present­day horses. Homologies include similarities in structure, development, and DNA sequences in different organisms. Vestigial structures are homologous structures that have a reduced function or no function at all. Examples include the pelvic bones of whales.

The geographic distribution of species, such as the high concentration of marsupial mammals in Australia, can provide evidence about common ancestors. In addition, the endemic species found on many island chains yield information about evolution on those islands.

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Part B ­ Phylogenetic trees and geographic relationships

The island fox, Urocyon littoralis, is endemic to the Channel Islands, which are located off the coast of southern California. Six of the eight Channel Islands support fox populations, and each of these islands is home to a distinct subspecies, as shown in the table below.

The island fox shares a common ancestor with the gray fox, Urocyon cinereoargenteus, which is found on the mainland. Both species have similar coloration and a diploid chromosome number of 66. One structural difference between the two species is the reduced size of the island fox, a feature known as dwarfism. The various island subspecies also differ from each other in size, number of tail vertebrae, and other characteristics.

The phylogenetic tree below shows the evolutionary relationships between the island fox subspecies and the gray fox. Drag the labels to their appropriate locations on the tree.

First, drag the blue labels onto the blue targets to identify the common ancestors at the branch points.

Next, drag one white label onto the white target to identify the homologous characteristic.

Then, drag one pink label onto the pink target to identify the relationship between the two species.

Hint 1. How to read a phylogenetic tree

A phylogenetic tree is a diagram that reflects evolutionary relationships among groups of organisms. Each branch point in the tree represents the common ancestor of the lineages beginning at that point or to the right of it. In the tree below, branch point 1 represents the common ancestor of species A, B, and C, whereas branch point 2 represents the common ancestor of species B and C.

A hatch mark in a phylogenetic tree represents a homologous characteristic shared by all the groups to the right of the mark. In this example, the hatch mark indicates a homologous characteristic shared by species B and C; that characteristic is not found in species A.

In the tree below, species B and C are more closely related than species A and B because they share the more recent common ancestor.

Hint 2. How can you determine the relatedness of species on a phylogenetic tree?

Based on the information in the tree below, rank the given pairs of species from most closely related to least closely related.

Rank the pairs from most closely related to least closely related.

ANSWER:

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most closely relatedleast closely related

Species D and Species E Species C and Species D Species B and Species C Species A and Species B

Hint 3. Can you place homologous characteristics on a phylogenetic tree?

The following table lists characters of five imaginary animal species. A check­mark (√) indicates the presence of a character, and a dash (−) indicates the absence of a character.

Add the characters to the appropriate places on the phylogenetic tree shown below. Drag the labels onto the phylogenetic tree. ANSWER:

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ANSWER:

Correct

One notable difference between gray foxes and island foxes is the small size of island foxes. This character (dwarfism) was exhibited by the common ancestor of all six island fox subspecies. Note that the northern Channel Island fox subspecies are more closely related to each other than to any of the southern subspecies, and that the southern subspecies are more closely related to each other than to the northern subspecies.

Part C ­ Natural selection in monkey flowers

Some monkey flowers (Mimulus guttatus) living near the sites of copper mines can grow in soil containing high concentrations of copper, which is toxic to most plants. Copper tolerance is a heritable trait.

The map below shows the area near an old copper mine, which contaminated the nearby soil with copper. A stream flows past the mine toward the lake at the bottom right of the map.

Use the map to determine which of the statements below are true.

Select the three statements that are true.

Hint 1. Process of natural selection

Natural selection includes the following main ideas:

Individuals within a population vary.

Much of the variation is due to heritable traits.

In any given environment, some heritable traits give individuals a higher probability of surviving and reproducing.

Individuals that have such traits tend to leave more offspring than other individuals.

Therefore, the frequency of favorable traits increases in the population over generations.

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Hint 2. Can you outline the steps in natural selection in another example?

The increased frequency of copper tolerance in monkey flowers can be compared to the increased frequency of drug resistance in bacteria. What are the steps leading to drug resistance in a population of bacteria?

Drag the labels to their appropriate labels on the flowchart.

ANSWER:

ANSWER:

Copper contamination in the soil created copper­tolerant plants.

Copper­tolerant plants are found only in contaminated soils.

The population that existed before mining must have included both copper­tolerant and copper­intolerant plants.

Nearly 100% of monkey flowers growing in copper­contaminated soil are copper tolerant.

Natural selection favors copper tolerance in all soils near the old mine, not only in the contaminated soils.

If you were to test monkey flowers growing on the shore of the lake, you would expect nearly 100% of them to be copper tolerant.

Correct

Copper tolerance in monkey flowers is an example of a direct observation of evolution. Natural selection favors the survival and reproduction of copper­ tolerant plants in copper­contaminated soils. Therefore, the allele for copper tolerance must have been present in some plants when the soil became contaminated. Because copper tolerance provides no benefit to plants in uncontaminated soils, the trait is not as common in plant populations growing outside the contaminated area.

Chapter 22 Question 19

Part A

Parasitic species tend to have simple morphologies. Which of the following statements best explains this observation?

ANSWER:

Parasites have not yet had time to progress, because they are young evolutionarily.

Simple morphologies convey some advantage in most parasites.

Parasites are lower organisms, and this is why they have simple morphologies.

Parasites do not live long enough to inherit acquired characteristics.

Correct

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Chapter 22 Question 12

Part A

Starting from the wild mustard Brassica oleracea, breeders have created the strains known as Brussels sprouts, broccoli, kale, and cabbage. Therefore, which of the following statements is correct?

ANSWER:

Natural selection is rare in wild populations of wild mustard.

In this wild mustard, there is enough heritable variation to permit these different varieties.

In wild mustard, most of the variation is due to differences in soil or other aspects of the environment.

Heritable variation is low in wild mustard–otherwise this wild strain would have different characteristics.

Correct

Misconception Question 106

Part A

What is the meaning of Darwin’s expression “descent with modification”?

ANSWER:

Descent with modification refers to the partial resemblance of offspring to their parents.

Descent with modification refers to natural selection.

Descent with modification refers to evolutionary change over time.

Correct

Darwin used this term to describe change in organisms over time, or evolutionary change.

Activity: Artificial Selection

Click here to complete this activity.

Then answer the questions.

Part A

Which of the following statements about natural selection is true?

Hint 1.

What conditions must be met for natural selection to occur?

ANSWER:

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Natural selection occurs in opposition to evolution.

Natural selection is a process whereby genes are selected randomly for preservation in the next generation.

Natural selection can be used by farmers to generate organisms with desirable traits.

Natural selection favors individuals that reproduce more than others.

Correct

Individuals who are better able to survive and reproduce are more likely to be selected for than individuals who don’t survive or cannot reproduce.

Part B

Which term describes a trait that increases an individual’s ability to survive in a particular environment?

Hint 1.

How do individuals change to accommodate their environment?

ANSWER:

Fitness

Evolution

Heritability

Adaptation

Correct

An adaptation is a trait that increases an individual’s ability to survive in a particular environment.

Part C

Which term describes the ability of a trait to be passed on to offspring?

Hint 1.

How do offspring obtain traits from their parents?

ANSWER:

Heritability

Fitness

Evolution

Adaptation

Correct

Heritability is the ability of a trait to be passed on to offspring.

Part D

Which of the following organisms could be produced by artificial selection?

Hint 1.

Remember that artificial selection only works for heritable traits.

ANSWER:

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A rabbit that is housebroken.

A chimpanzee that communicates through sign language.

A cow that produces a large quantity of milk.

A dog that serves as the “eyes” for a blind individual.

Correct

A cow’s ability to produce milk is a heritable trait that can be manipulated by artificial selection.

Part E

Which pair of chickens should a farmer breed to produce larger chickens?

Hint 1.

Consider which parental animals have the traits desired in the offspring.

ANSWER:

Large hen, small rooster

Large hen, large rooster

Small hen, large rooster

Small hen, small rooster

Correct

Large parents should be bred to produce larger offspring.

Part F

A farmer wishes to develop a strain of high­yield corn that is also resistant to drought. He has the following individuals from the current year’s crop:

Individual A—Yield: 179 bushels/acre; drought resistance: high

Individual B—Yield: 220 bushels/acre; drought resistance: low

Individual C—Yield: 185 bushels/acre; drought resistance: medium

Individual D—Yield: 140 bushels/acre; drought resistance: high

Individual E—Yield: 200 bushels/acre; drought resistance: medium

Which of the following crosses would produce the highest corn yield with the highest resistance to drought?

Hint 1.

Determine the average yield and drought resistance expected from each cross.

ANSWER:

C and E

A and B

B and B

A and E

Correct

This cross would result in an average corn yield of 189.5 bushels/acre and have a medium­high drought resistance, which is the best you can get for both traits.

Chapter 22 Question 14

Part A

2017/3/30Chapter 22 ­ Descent With modification HW

Which of these conditions are always true of populations evolving due to natural selection?

Condition 1: The population must vary in traits that are heritable.

Condition 2: Some heritable traits must increase reproductive success.

Condition 3: Individuals pass on most traits that they acquire during their lifetime.

ANSWER:

Condition 2 only

Conditions 1 and 2

Conditions 2 and 3

Condition 1 only

Correct

Misconception Question 107

Part A

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of Staphylococcus aureus, but within two years, methicillin­resistant strains of S. aureus (MRSA) appeared. How did the resistant strains of S. aureus emerge?

ANSWER:

In response to treatment of Staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. These bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common.

Staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common.

In response to treatment of Staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.

Correct

Evolutionary change comes about as the proportion of individuals in the population displaying a particular trait increases from generation to generation.

Misconception Question 108

Part A

Soapberry bugs use needlelike “beaks” to feed on seeds within the fruits of various plants. Bugs feed most successfully when their beak length matches the size of the fruit on which they are feeding. For 25 years, populations of soapberry bugs in central Florida have been feeding on small goldenrain tree fruits that were introduced to the area, rather than on the larger native balloon vine fruits that serve as food for other soapberry bug populations. Beak lengths of

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soapberry bugs are variable, but the average beak length is shorter in soapberry bug populations that feed on goldenrain tree fruits than in populations that feed on balloon vine fruits, as shown in the graph. How does natural selection act on beak length in soapberry bug populations?

ANSWER:

Natural selection decreases beak length in soapberry bug populations.

Natural selection increases beak length in soapberry bug populations.

The action of natural selection on beak length in soapberry bug populations varies with the environment.

Correct

Traits favored by natural selection may change as the environment in which a population lives changes. Selection and adaptation must always be discussed in the context of a particular environment. Soapberry bugs feed most effectively when their beak length closely matches the size of the seed­ containing fruit. In central Florida, where soapberry bugs feed on small goldenrain tree fruits, natural selection has reduced average beak length in the population of bugs. However, in Louisiana, where soapberry bugs feed on larger fruits, natural selection has increased average beak length in the population of bugs.

Score Summary:

Your score on this assignment is 100%.

You received 9 out of a possible total of 9 points.

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