Two Animals Are Considered Members Of Different Species If They _____.

Chapter 24 Homework

Feathers either play a role, or may have played a role, in _____.courtship
gliding
extended hops
flight
all of these

Correct
All of these are, or may have been, functions of feathers.

Part B
_____ is rapid speciation under conditions in which there is little competition.
Adaptive radiation

Adaptive radiation is rapid speciation under conditions in which there is little competition.

Part C
Mass extinctions create conditions that promote _____.
adaptive radiation
Mass extinctions reduce competition and allow for periods of rapid speciation.
Part D
The appearance of an evolutionary novelty promotes _____.
The appearance of an evolutionary novelty may allow for the exploitation of previously unexploited niches.
Part E
The different finch species found on the Galápagos Islands probably arose as a result of _____.
adaptive radiation
The finches that initially immigrated to the Galápagos Islands experienced little competition, the result of which was the promotion of speciation.
Part A
What is the most important factor that holds a gene pool of a species together and prevents speciation?
gene flow
Gene flow refers to the transfer of alleles among populations. As long as populations are exchanging alleles, speciation is unlikely.
Part A
Two animals are considered members of different species if they _____.
cannot mate and produce viable, fertile offspring
If two individuals cannot interbreed and produce viable, fertile offspring, they are members of different species.
Part A
Macroevolution is _____.
evolution above the species level
Part A
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
Part A
Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. These two frog species separate by _____.
reduced hybrid viability
Part A
What is genetic drift?
A change in allele frequencies caused by random events
Genetic drift is a random change in allele frequencies over time.
Part B
Why are the large finches now living on the Galápagos Islands different from the original source population from a nearby island?
All three answers are correct.
Genetic drift occurred in the two populations.
Natural selection favored individuals that were more fit in the new environment.
The separation of habitats reduced gene flow between the populations.

Physical isolation, natural selection, and genetic drift are all events that lead to speciation

Part C
True or false? The last ice age produced many different species mainly because populations dispersed and colonized new habitats.
False
The last ice age produced many different species mainly because of vicariance events; the glaciers physically separated populations from each other.
Which of the following statements about reinforcement is true?Reinforcement is a type of natural selection.

Reinforcement is a type of natural selection called disruptive selection, which favors extreme phenotypes over intermediate phenotypes.

Part E
A subset of a population of birds leaves its habitat on the mainland and colonizes a nearby island. The birds, after a period of time, become reproductively isolated. The island sinks and the population of birds that lived on the island returns to its original habitat. Which of the following statements about these bird populations is true?
The populations will not be able to interbreed because they are different species.

Different species cannot interbreed.

Part F
A population of birds colonizes an area in which the insects upon which they feed live inside trees. Which of the following events accounts for an observed increase in average beak size in the bird population over time?
Increased fitness of large-beaked birds, leading to natural selection

Birds with larger beaks are better able to survive in the new environment.

Part G
True or false? A flood that separates a population of frogs onto opposite sides of a lake is an example of a vicariance event that may result in allopatric speciation.
True

Allopatric speciation may occur when populations are separated geographically; this type of speciation can begin with a vicariance event, in which a geographic barrier such as water isolates a population, or a dispersal event, in which a subset of a population migrates to a different habitat.

Part A
Of the 59 matings in the experimental groups, how many were between like-adapted flies (flies adapted to the same medium)?
42
Part B
Which of the following statements is best supported by the data on matings in the experimental groups?
not different species, but a reproductive barrier is forming between the populations.
Part C
Which of the following statements is supported by the data from the control group matings?
Flies were about as likely to mate with flies from different starch-adapted populations as with flies from their own starch-adapted population.
Part D
A similar control experiment was performed with flies adapted to maltose, and similar results were obtained. What were these control experiments testing?
These control experiments tested whether flies were more likely to choose mates from their own population than from another population adapted to the same medium.
Part A
According to the _____ model, evolution occurs in spurts; species evolve relatively rapidly then remain unchanged for long periods.
punctuated equilibrium

This is the definition of punctuated equilibrium.

Part A
Other than predation by introduced Nile perch, the most likely explanation for the recent decline in cichlid species diversity in Lake Victoria is _____.
fusion
Speciation _____.can involve changes to a single gene
Part A
According to most paleoanthropologists, which of the following is true?
When modern humans arose, archaic humans disappeared in Africa.
Part B
If your pituitary gland isn’t functioning properly, which of the following will be affected?
reproduction and growth
Part C
You are a paleoanthropologist studying Neanderthals. Where should you look for their fossils?
Europe
What do paleoanthropologists generally believe about genetic findings?Genetic findings need corresponding fossil evidence to be true.
Part E
How do genomes of species change?
By mutations in DNA.
Part A
Which of the following factors would not contribute to allopatric speciation?
Gene flow between the two populations is extensive.
How long does it take new species to form on Earth?The time required varies considerably.
Read examples of both rapid and slow speciation events.
Part A
Adaptive radiations on archipelagos (island chains) represent some of the best-understood speciation events. Why is an ancestral species more likely to give rise to multiple descendent species on an archipelago than on an equal-sized area of mainland?
Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland.

Regions that are highly subdivided by geographic barriers such as archipelagos typically have more species than do regions with fewer barriers. The barriers lead to reproductive isolation between populations, initiating allopatric speciation.

Part A
Which of the following is the first step in allopatric speciation?
geographic isolation

Allopatric speciation occurs when a population of organisms is geographically separated long enough for significant changes to occur. After a period of time, the populations may no longer be able to interbreed.

Part A
Use the following information to answer the question(s) below.

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
Part A
Use the following information to answer the question(s) below.

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.

The two populations are _____.

different subspecies, under the morphological species concept
Part A
Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?
a behavioral reproductive isolating mechanism
Part A
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
Part A
Use the following information to answer the question(s) below.

About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other’s closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.)

Refer to the paragraph about the formation of the Isthmus of Panama. If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?

greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water
Part A
Use the following description to answer the question(s) below.

In the ocean, on either side of the Isthmus of Panama, are thirty species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are fifteen species on the Pacific side and fifteen different species on the Atlantic side. The Isthmus of Panama started rising about ten million years ago. The oceans were completely separated by the isthmus about three million years ago.

In the following figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

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
Does geographic distance between salamander populations increase their reproductive isolation?
To answer this question, researchers studied populations of the dusky salamander (Desmognathus ochrophaeus) living on different mountain ranges in the southern Appalachian Mountains.
The researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. Four mating combinations were tested for each pair of populations (A and B)—two within the same population (female A with male A and female B with male B) and two between populations (female A with male B and female B with male A).
The proportion of successful matings for each mating combination was measured. For example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. Then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). The reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (AA + BB) minus the sum of the proportion of successful matings of each type between populations (AB + BA).
The table (Figure 1) provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.
Part A – Understanding experimental design
What hypothesis did the researchers test in this study?
Reproductive isolation increases with geographic distance between dusky salamander populations.
Part B
Identify the independent variable in this study.
the geographic distance between dusky salamander populations
Part C
Identify the dependent variable in this study.
the reproductive isolation values for pairs of dusky salamander populations
Part D
Why did the researchers set up four possible matings for each pair of populations: female A + male A; female B + male B; female A + male B; female B + male A?
to compare the proportion of successful matings within populations to the proportion of successful matings between populations
Part E – Calculating reproductive isolation values
Calculate the value of the reproductive isolation index if all of the matings within a population were successful but none of the matings between populations were successful.
2.0

The reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (AA + BB) minus the sum of the proportion of successful matings of each type between populations (AB + BA). In this case, (1 + 1) – (0 + 0) = 2.

Calculate the value of the reproductive isolation index if salamanders were equally successful in mating with members of their own population and members of another population.The reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (AA + BB) minus the sum of the proportion of successful matings of each type between populations (AB + BA). In this case, (AA + BB) = (AB + BA), so (AA + BB) – (AB + BA) = 0.
Part G – Interpreting a scatter plot
Review the scatter plot (Figure 2) of reproductive isolation value versus geographic distance for 27 pairs of dusky salamander populations. (Select Figure 2 from the drop-down menu above the data table.)
How do reproductive isolation values change with geographic distance among pairs of dusky salamander populations?
Reproductive isolation values increase with geographic distance.
Part H
What does the scatter plot suggest about the process of allopatric speciation?
Reproductive isolation is more likely to occur as populations become separated by greater distances.

Such experiments provide information about the early stages of allopatric speciation.

Evaluating hypotheses
Which hypothesis suggests a possible cause of the relationship shown in the scatter plot?
Geographically separated populations of dusky salamanders gradually diverge, and the divergence increases with geographic distance.
Part A
According to the concept of punctuated equilibrium, _____.
a new species accumulates most of its unique features as it comes into existence
Part C
You are a paleoanthropologist studying Neanderthals. Where should you look for their fossils?