Chapters 24-26

Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees.

What keeps the two populations separate?

habitat isolation

If biological species are defined in terms of reproductive compatibility, the formation of a new species hinges on ________.

reproductive isolation

Which of the following statements describes mechanical isolation prezygotic barrier?

two snails have shells that spiral in different directions

Many songbirds breed in North America in the spring and summer and then migrate to Central and South America in the fall. They spend the winter in these warmer areas, where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

Their winter habitat has no bearing on their degree of reproductive isolation.

The peppered moth provides a well-known example of natural selection. The light-colored form of the moth was predominant in England before the Industrial Revolution. In the mid-19th century, a dark-colored form appeared. The difference is produced by a dominant allele of one gene. By about 1900, approximately 90% of the moths around industrial areas were dark colored, whereas light-colored moths were still abundant elsewhere. Apparently, birds could readily find the light moths against the soot-darkened background in industrial areas and, therefore, were eating more light moths. Recently, use of cleaner fuels has greatly reduced soot in the landscape, and the dark-colored moths have been disappearing. Should the two forms of moths be considered separate species?

No; they still can interbreed.

Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms?

habitat isolation

Rank the following in order from most general to most specific.

1. gametic isolation
2. reproductive isolating mechanism
3. sperm-egg incompatibility in sea urchins
4. prezygotic isolating mechanism

2, 4, 1, 3

The production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) is an example of _____.

reduced hybrid fertility

Which postzygotic barriers prevent formation of hybrids beyond the first generations?

hybrid breakdown

A river could potentially be a geographic barrier that causes allopatric speciation. Which of these organisms is LEAST likely to overcome such a barrier?

small rodents

How are two different species most likely to evolve from one ancestral species?

allopatrically, after the ancestral species has split into two populations

House finches were found only in western North America until 1939, when a few individuals were released in New York City. These individuals established a breeding population and gradually expanded their range. The western population also expanded its range somewhat eastward, and the two populations have recently come in contact. If the two forms were unable to interbreed when their expanding ranges met, it would be an example of _____.

allopatric speciation

How can reproductive barriers form sympatric populations while their members remain in the same geographic area?

polyploidy

The difference between geographic isolation and habitat differentiation (isolation) is the ________.

relative location of two populations as speciation occurs

In which habitat should one find snapping shrimp most closely related to shrimp that live in habitat A4?

B4

Which of these habitats is likely to harbor the most recently diverged species?

A1

Which habitats should harbor snapping shrimp species with the greatest degree of genetic divergence from each other?

A5 and B5

Which factor is most important for explaining why there are equal numbers of snapping shrimp species on either side of the isthmus?

the relative shortness of time they have been separated

According to the biological species concept, for speciation to occur, ________.

at least one gene, affecting one reproductive barrier, must change

Which conclusion can be drawn from this evolutionary tree?

A single clade (that is, a group of species that share a common ancestor) can include species that formed by gradualism and other species that formed by punctuated equilibrium.

In the accompanying diagram, the original population of a species of fish in a small lake that lacks predators is shown at the top. After separation by a land mass, the figure at the bottom left of the diagram shows the resulting change. Each color represents a different species. Allopatric speciation occurs when gene flow is disrupted through physical isolation of the original population. Although generally less common, sympatric speciation can occur among individuals in a population living in the same area, such as seen in the bottom right of the figure. Which of the following scenarios would most likely cause sympatric speciation to occur?    

A mutation that resulted in darker coloration affecting female mate choice.

Which of the following factors would not contribute to allopatric speciation?

Gene flow between the two populations is extensive.

How does continental drift explain the uniqueness of Australian fauna?

The subsequent separation of the southern continents formed an island of marsupials.

Which tree shows the greatest evolutionary distance between chytrids and ascomycetes?

I

In the phylogenetic trees, numbers represent species, and the same species are shown in both trees. Which two species are represented as sister species in Tree 2 but are not shown as sister species in Tree 1?

3 and 4

If organisms A, B, and C belong to the same class but to different orders and if organisms C, D, and E belong to the same order but to different families, which of the following pairs of organisms would be expected to show the greatest degree of structural homology?

D and E

Which of the following changes would a modern systematist be most likely to make after learning of the results of the rRNA analyses?

break the species G. intestinalis into four separate species, A, B, C, and D

Which of the following trees, if any, depicts the same relationship among species as shown above?

GFED CBA

Refer to the figure. Which of the following forms a monophyletic group?

E, F, and G

Given that phylogenies are based on shared derived characteristics, which of the following traits is useful in generating a phylogeny of species W, X, Y, and Z?

Trait 2

If the figure is an accurate depiction of relatedness, then which of the following should be an accurate statement?

If all species depicted here make up a taxon, this taxon is monophyletic.

Based on the tabular data, and assuming that time advances vertically, which phylogenetic tree is the most likely depiction of the evolutionary relationships among these five species?

EBCDA

Regarding these sequence homology data, the principle of maximum parsimony would be applicable in _____.

inferring evolutionary relatedness from the number of sequence differences

The lakes of northern Minnesota are home to many similar species of damselflies of the genus Enallagma. These species have apparently undergone speciation from ancestral stock since the last glacial retreat about 10 thousand years ago. Sequencing which of the following would probably be most useful in sorting out evolutionary relationships among these closely related species?

mitochondrial DNA

The most important feature that permits a gene to act as a molecular clock is _____.

a reliable average rate of mutation

Which of the following would, if it had acted upon a gene, prevent this gene from acting as a reliable molecular clock?

natural selection

What kind of evidence has recently made it necessary to assign the prokaryotes to either of two different domains, rather than assigning all prokaryotes to the same kingdom?

rRNA genes

Examine the figure. If you were a graduate student trying to develop a thesis project that would resolve polytomies, which of the following groups would you study?

forams, red algae, and amoebas

These data would support which of the following conclusions?

Eukaryotes are more similar to archaea than to bacteria.

If you were the evolutionary biologist in charge of a project to create a phylogenetic tree that better clarified the evolutionary relationships between the species listed in the accompanying figure, what would be a logical first step?

Evaluate evidence to determine the relationships of species D, E, and F.

As the evolutionary biologist in charge of a student project to create a phylogenetic tree that better clarified the evolutionary relationships between the species listed in the accompanying figure, you asked the students to pose a question that would be a logical first step to better understand the evolutionary history of the group. Which student question would be the best starting point?  

 Can we evaluate evidence to determine the relationships of species D, E, and F?    

Which of these are homologous structures?

Ivy leaf and pine needle

This figure shows a phylogenetic tree of birds and their close relatives. Identify the monophyletic taxon.

Birds and dinosaurs and their common ancestor

Select the correct statement about phylogenetic trees.

Phylogenetic trees may expand quickly to maximum width and then narrow over time.

This phylogenetic tree was constructed by comparing sequences for a homologous gene involved in development. Select the correct statement.

The nucleotide sequence of this gene in a mouse is more similar to the sequence in a chicken, and both are less similar to the nucleotide sequence of this gene in a frog.