BSC 2010 Ch. 17

How is an allopolyploid plant formed?
Two plants of different species interbreed to form a plant of a new species
How would you expect the rate of speciation of an allopatric case to compare to the rate of speciation of a sympatric case involving formation of allopolyploid offspring?
The allopatric case would occur at a much slower rate than the sympatric case involving allopolyploid offspring.
What is polyploidy?
The condition of having more than the normal number of chromosomes
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How do allopatric and sympatric speciation differ?
Allopatric speciation involves a physical separation of groups as they form new species; sympatric speciation does not
Ernst Mayr’s biological species concept
does not apply to organisms that reproduce asexually
Which statement about the morphological species concept is true?
Linneaus used one
Which species concept most emphasizes the evolutionary history of species?
The lineage species concept
In the Dobzhansky-Muller model, an ancestral population (aabb) splits into two lineages. Different mutations produce different new alleles in each population (Aabb in one population, aaBb in the other). All of the following genotypes would be viable except
AaBb
The Dobzhansky-Muller model
emphasizes gene interaction
All of the following statements about speciation are true except
evolution always occurs in speciation
Which of the following is least likely to lead to allopatric isolation?
A small lake dividing a population of butterflies
Geographic isolation
may decrease the probability, over time, that members of two separated populations can mate
Which sequence of events is most likely in allopatric isolation?
Geographic barrier, genetic divergence, reproductive isolation
Darwin’s finches on the Galapagos Islands have diverged primarily via _____ speciation, and exhibit diverse morphologies owing to differences in _____
allopatric; their diets
A butterfly is separating into two different groups- one that lays eggs in the understory of bushes and the other that lays eggs in the tops of bushes. This butterfly species is most likely experiencing
sympatric speciation
Which statement about polyploidy in plants is true?
Allopolyploids are hybrid plants that result from the mating of two closely related species
The distinction between prezygotic and postzygotic isolation is whether
The isolation occurs before or after fertilization
Two geographically separated populations of butterflies begin to diverge in the time of day they are active. One group is active earlier in the day, and the other is active later. If this separation were to continue, it would most likely contribute to _____ isolation.
temporal
Prezygotic isolating mechanisms can arise from all of the following except
low fertility of hybrids
Refer to the figure below, which shows the frequencies of mating calls in two frogs in areas where they are in sympatry and areas where they are in allopatry. The mating calls are ______ diverged in regions of sympatry. Based on this result, one might predict that there has been selection to _______ prezygotic isolation in regions of sympatry, a phenomenon known as _______.
more; increase; reinforcement
Suppose that the natural ranges of horses and donkeys were to overlap. Which of the following statements best describes what would likely happen to the populations over time?
Because their hybrid offspring are not reproductively fit, reinforcement could strengthen prezygotic barriers
Two populations that were once isolated come into contact. Which of the following statements about what might happen after contact is false?
If hybrids are unfit, reinforcement of prezygotic barriers would be disfavored
Which is least likely to evolve via direct natural selection?
Hybrid infertility
Persistent hybrid zones, like those found in Bombina frogs in Europe, stay narrow due to
low hybrid adult viability

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