Deck 13: The Origin of Species

Question 1

A geographic barrier that only partially isolates two populations, so that gene flow is reduced but not eliminated, may lead to

A) allopatric speciation.
B) sympatric speciation.
C) parapatric speciation.
D) none of the above

Answer 1

C

Question 2

Which of the following is a barrier to gene flow that occurs before mating occurs?

A) hybrid inviability
B) gametic isolation
C) ecological inviability
D) mechanical isolation

Answer 2

D

Question 3

Which of the following is true regarding "magic traits"?

A) In the early stages of speciation, species should differ only in regions of the genome containing genes for magic traits.
B) In the early stages of speciation, there should be fairly uniform divergence across each species' genome.
C) In the later stages of speciation, species should differ only in regions of the genome containing genes for magic traits.
D) At any stage in speciation, species should differ only in regions of the genome containing genes for magic traits.

Answer 3

A

Question 4

Why is it unusual for one species of caterpillar to feed on a wide range of plants?

A) Caterpillars are usually well adapted to the defensive chemicals of certain plant species.
B) Caterpillars are not able to travel far enough to consume multiple species of plants.
C) Different plants offer different nutritional resources.
D) It is not unusual; most caterpillar species feed on many different plant species.

Question 5

Which species concept(s) would be most useful for a conservation biologist?

A) phylogenetic species concept
B) biological species concept
C) general lineage species concept
D) a and c
E) a, b, and c

Question 6

The ________ species concept cannot be used to define bacteria and archaea because organisms in these domains reproduce ________.

A) biological; asexually
B) general lineage; asexually
C) biological; sexually
D) phylogenetic; sexually

Question 7

Extrinsic postzygotic isolation is most likely when

A) parental populations are adapted to similar environments.
B) parental populations are adapted to divergent environments.
C) genetic drift is strong.
D) gene flow between parental populations is high.

Question 8

A pair of insect species inhabits the same community, but one lives on goldenrod plants and the other on autumn daisies and rarely leave their preferred type of plant. This is an example of ________ isolation, which is a ________ barrier to gene flow

A) gametic; prezygotic
B) gametic; postzygotic
C) habitat; prezygotic
D) habitat; postzygotic
E) behavioral; prezygotic

Question 9

How do researchers make an initial determination about which microbes are different species using the phylogenetic species concept?

A) by examining the potential for microbial species to swap genetic information
B) by comparing the gene pool of different metapopulations within a lineage
C) by using a gene shared across the entire tree of life to compare lineages
D) by comparing observable traits such as morphology or staining characteristics

Question 10

Many butterflies in the genus Heliconius are mimetic, which means that they closely mimic the wing patterning and color of highly poisonous species even though they themselves are not poisonous. This is a benefit because many predators (such as birds) learn to avoid poisonous species by identifying their wing patterns and colors. Some closely related Heliconius species mimic different poisonous species. Although they can successfully hybridize and produce viable/fertile offspring that have high fitness in the laboratory, the hybrids are intermediate in wing patterning and color and are not good mimics. Consequently, they have low fitness in nature. This is an example of

A) intrinsic postzygotic isolation.
B) extrinsic postzygotic isolation.
C) habitat isolation.
D) prezygotic isolation.

Question 11

Which of the following would provide evidence for reinforcement?

A) Pre-mating isolation between two species is higher in areas where they are sympatric than in areas where they are allopatric; postzygotic isolation is strong in all crosses.
B) Postzygotic isolation between two species is higher in areas where they are sympatric than in areas where they are allopatric; pre-mating isolation is the same in allopatric and sympatric populations.
C) Pre-mating isolation between two species is higher in sympatry than in allopatry; there is no postzygotic isolation in any cross.
D) a and c

Question 12

A river that divides a population of terrestrial salamanders could lead to

A) allopatric speciation.
B) sympatric speciation.
C) parapatric speciation.
D) none of the above

Question 13

Early classifications of the polar bear were based on

A) reproductive isolation from brown bears.
B) evolutionary history.
C) appearance and behavior.
D) metapopulations that exchange alleles.

Question 14

Which species concept would assign isolated giraffe populations with little gene flow to separate species based on differences in mitochondrial DNA between the populations

A) the biological species concept.
B) the general lineage species concept.
C) the phylogenetic species concept.
D) all of the above

Question 15

Under the biological species concept,

A) a species represents a group of interbreeding (or potentially interbreeding) populations that are reproductively isolated from other such groups.
B) different species do not exchange genes.
C) a and b
D) neither a nor b

Question 16

Which of the following is not true regarding the accumulation of genetic differences in allopatric populations?

A) Drift and selection cause allele frequencies to change differently in isolated populations.
B) Mutations at certain loci may lead to incompatibilities between populations.
C) Certain mutations may change the behavioral preference of mating individuals.
D) Genetic differences are irrelevant once the populations are no longer separated.

Question 17

How did the formation of the Isthmus of Panama influence the speciation of shrimp?

A) The isthmus presented a geographic barrier to gene flow, reproductively isolating the shrimp.
B) The isthmus allowed the shrimp to evolve in allopatry.
C) The isthmus united two reproductively isolated populations of shrimp.
D) a and b
E) a and c

Question 18

Which of the following is not an example of horizontal gene transfer?

A) the transmission of genetic material from one bacterium to another via a bacteriophage virus
B) the exchange of plasmid DNA via sex pili between two different bacteriophages
C) the transmission of genetic material from parent to daughter bacterial cells
D) the incorporation of exogenous genetic material by a bacterium from the surrounding environment

Question 19

Which of the following conditions is/are thought to be necessary for sympatric speciation to occur?

A) disruptive selection
B) stabilizing selection
C) a and b
D) neither a nor b

Question 20

An allele is experiencing positive selection when

A) it decreases in frequency in a population due to selection.
B) it increases in frequency in a population due to selection.
C) its average excess in fitness of is greater than zero.
D) a and c
E) b and c

Question 21

You are studying speciation in crickets. You find that males and females from different populations will mate, but few eggs get fertilized. This is an example of what type of reproductive isolating barrier?

A) pre-mating
B) post-mating, prezygotic
C) intrinsic postzygotic
D) extrinsic postzygotic

Question 22

What evidence did Janzen and colleagues find while studying the neotropical skipper butterfly, Astraptes fulgerator, that led them to test whether it was a cryptic species. What are the implications of their findings?

Question 23

The stable ecotype model is useful because

A) it applies ecological speciation to microbial species.
B) ecological and genetic clusters of microbes correspond to each other.
C) there are no other possible ways to define a microbial species.
D) a and b
E) b and c

Question 24

What do hybridization studies on Drosophila melanogaster tell us about how long it takes reproductive barriers to lead to new fly species?

A) It takes a long time for these flies to become isolated enough to be considered a new species.
B) Postzygotic isolation often evolves faster than prezygotic isolation in flies.
C) It takes a short time for these flies to become isolated enough to be considered a new species.
D) a and b
E) b and c

Question 25

About what percentage of genes are essential for all strains of Escherichia coli?

A) 3%
B) 50%
C) 97%
D) 100%

Question 26

Shapiro's variation on the stable ecotype model is most analogous to which species concept?

A) phylogenetic species concept
B) biological species concept
C) general lineage species concept
D) none of the above

Question 27

Which species concept(s) focus(es) focuses primarily on the reproductive isolation of populations?

A) phylogenetic species concept
B) biological species concept
C) general lineage species concept
D) a and b
E) a and c

Question 28

Evidence that sexual selection may play an important role in speciation of Hawaiian swordtail crickets includes the fact that

A) genetic variation in male song and female preference created a reproductive barrier.
B) crickets only diverged ecologically when colonizing new islands.
C) genetic variation in male song was not accompanied by variation in female preference.
D) genetic variation in female preference did not influence gene flow between populations.

Question 29

In the monkeyflowers studied by Bradshaw and Schemske, reproductive isolation results from

A) gametic incompatibility between pollen and ovule.
B) sterility of hybrid offspring.
C) color preferences of hummingbirds and bees.
D) asynchrony in time in which plants reach reproductive maturity.

Question 30

Which species concept(s) focus(es) on the evolutionary history of populations?

A) phylogenetic species concept
B) biological species concept
C) general lineage species concept
D) a and b
E) a and c

Question 31

Which statement regarding the parasitoid wasps that infect the cryptic skipper species of Costa Rican butterflies is true?

A) The wasps lay eggs in adult skipper hosts.
B) The wasps are not a cryptic species as well, although they are species specific to cryptic skippers.
C) The wasps are cryptic species as well, with DNA barcoding revealing a possible 313 species.
D) none of the above; there are no parasitoid wasps of skipper caterpillars

Question 32

What does the phylogeny of swordtail cricket species in Hawaii reveal about speciation?

A) The more derived crickets are found on the oldest islands.
B) Early lineages from the older islands independently colonized the younger islands.
C) Cricket species frequently move between older and younger islands to interbreed.
D) Early lineages from younger islands independently colonized the older islands.

Question 33

You are studying a potential case of incipient sympatric speciation involving two morphs of a cichlid fish in a crater lake that feed at different depths and differ in morphology. If true, which of the following statements would make sympatric speciation more likely (or at least possible)? i. The two morphs specialize on different food types; matings between the morphs produce offspring that are intermediate and can efficiently utilize both food types.
Ii) The two morphs feed on different food types, and there is strong disruptive selection operating such that individuals that are intermediate are very strongly selected against (basically none survive).
Iii) Mating occurs in the area of the lake where each morph feeds. Also, females choose males based on jaw morphology, preferring males that have the same jaw morphology as the female.
Iv) The two morphs feed at different depths, but both morphs come to a rocky area near the shore to mate. Females prefer to mate with males of the other morph.

A) i, ii, iii, iv
B) i, iv
C) ii, iii
D) ii, iii, iv
E) i

Question 34

What reproductive isolating mechanism has led to speciation of palms on Lord Howe Island?

A) habitat isolation
B) temporal isolation
C) pollinator isolation
D) gametic isolation

Question 35

Species A has chromosome number 2n = 18, and species B has chromosome number 2n = 20. The two plants hybridize and produce viable offspring through allopolyploidy. What is the chromosome number of the viable offspring?

A) 2n = 18
B) 2n = 20
C) 2n = 38
D) 4n = 38

Question 36

Put the following stages of allopatric speciation in a terrestrial beetle population in the correct order. i. Mutation, drift, and selection act separately on the two subpopulations, and they become increasingly divergent.
Ii) A river dries up, and the population has continuous geographic range with reproductive barriers that reduce gene flow between certain individuals.
Iii) A river physically divides the population into two subpopulations.
Iv) The population has continuous geographic range with some genetic variation.

A) iv, ii, i, iii
B) iv, iii, i, ii
C) ii, iii, i, iv
D) ii, iii, iv, i

Question 37

What is a molecular clock?

A) a method used to determine time based on base pair substitutions
B) a method to deduce divergence time between lineages in a phylogeny
C) a method that can be calibrated with other markers of time, like fossils with known ages
D) all of the above

Question 38

Which of the following is/are required to designate populations as separate species under the phylogenetic species concept?

A) Each population forms a monophyletic group.
B) Members all have the unique characteristics that define the species.
C) There is strong reproductive isolation between the populations.
D) a and b
E) a, b, and c

Question 39

Describe how ecological adaptation through changes in beak size leads to reproductive isolation between different species of Darwin's finches.

Question 40

The phylogenetic species concept may not be useful for microbial species because

A) microbes are not neatly divided by species barriers.
B) it is only useful if organisms reliably pass down genes to offspring.
C) the genomes of microbes are mixed together by horizontal gene transfer, resulting in a mosaic-like genome.
D) all of the above

Question 41

Describe how some biologists have proposed to use adaptation as a criterion for identifying bacterial species. What is a potential drawback of this approach?

Question 42

Discuss the definition of a bacterial species. You should include at least two species concepts that best characterize bacteria, explain what is important to take into account when defining bacteria, and explain the difficulties of the definition.

Question 43

You are studying 20 lake populations of the three-spined stickleback. In each lake, there are two distinct morphs that specialize on feeding in different areas of the lake. The benthic morph feeds around the shoreline, while the limnetic morph feeds in the open water. The environments and food sources in these environments are quite different. You hypothesize that these morphs are diverging into two different species in accordance with the ecological speciation model. Please describe an experiment that would allow you to test this hypothesis. Be sure to include what results would support and refute the ecological speciation hypothesis.

Question 44

Please provide a real or hypothetical example of (a) pre-mating, (b) post-mating, prezygotic, (c) intrinsic postzygotic, and (d) extrinsic postzygotic reproductive isolating barriers.

Question 45

Describe a situation where biologists using the phylogenetic species concept and those using the biological species concept would reach different conclusions on whether two populations represent different species.

Question 46

The biological, phylogenetic, and general lineage species concepts each have their strengths and weaknesses. Compare and contrast all three and evaluate them for their relative usefulness. Based on your answer, describe the recent speciation of polar bears and whether you think it is useful to call them a species separate from brown bears.

Question 47

Is the fact that many plant species are capable of self-fertilization is important in understanding why polyploid speciation is more common in plants than in animals? Explain why or why not.

Question 48

Allopatric speciation is probably the most common way that new species form. Please describe a hypothetical scenario in which an initial ancestral population could split to form a new species through allopatric speciation. A fully correct answer will incorporate the following terms: gene flow, divergence, natural selection (including sexual selection), genetic drift, reproductive isolation, and reinforcement.