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Evolution Exam #4-Chapter 16

Terms in this set (43)

Early classification systems from Aristotle to Linneaus would have been most like what we now call_____.
A) the morphospecies concept
B) the phylogenetic species concept
C) the biological species concept
D) the ecological species concept
A
The species concept that relies most heavily on the criterion that species are evolutionarily independent units that are isolated by gene flow is____.
A) the morphospecies concept
B) the phylogenetic species concept
C) the biological species concept
D) This criterion is common to all of these concepts.
D
Organisms such as prokaryotes (bacteria and archaea) - along with some eukaryotes - reproduce asexually. In the case of bacteria and archaea in particular, which exchange DNA but do not reproduce utilizing conventional sexual reproduction, the BEST way in which to define species is with ___.
A) the morphospecies concept
B) the phylogenetic species concept
C) the biological species concept
D) an ecological species concept
D
There are two closely related populations of squirrels living in the Grand Canyon area - one lives on the north rim, the other lives on the south rim. Speciation in these squirrels BEST fits which model?
A) dispersive allopatric speciation
B) dispersive sympatric speciation
C) vicariant allopatric speciation
D) vicariant sympatric speciation
C
Your textbook authors make the claim that "sympatric species with matching chromosome numbers are rare." Why is this?
A) because allopatric speciation is far more common
B) because sympatric speciation has only been hypothesized but not documented
C) because coexisting populations need a boundary to gene flow before divergence can occur, and differences in chromosome numbers provide this
D) because macroevolution is just a theory
C
Isolating mechanisms leading to speciation have been documented by ________.
A) geographic isolation
B) polyploidy
C) temporal isolation
D) a mutation in a single gene
E) All of the above
E
It now seems clear that the strongest factor in speciation events is ________.
A) genetic drift
B) sexual selection
C) natural selection
D) the bottleneck effect
C
Research on speciation of Hawaiian crickets, shown in the accompanying figure, has led researchers to conclude that ________.
A) these cricket species have diverged by a mechanism known as assortative mating
B) females of different species have strong preferences for the singing pulse rate of the males of their own species
C) female preference for male singing pulse rate is genetically linked to the combination of genes regulating the singing pulse rate of males
D) All of the above are accurate.
D
Factors such as behavioral, temporal, or ecological isolation mechanisms that prevent two closely related sympatric populations from interbreeding can be grouped together and classified as ________.
A) prezygotic isolating mechanisms
B) postzygotic isolating mechanisms
C) polyploidy hybrid speciation
D) adaptive radiation
A
Hybridization between populations upon secondary contact may result in ________.
A) reinforcement of the two original species by way of pre- or post-zygotic isolating mechanisms
B) the creation of one or more new species as hybrids between the two parental species
C) the creation of a hybrid lineage that has higher fitness than either of the parental species
D) All of the above are possible.
E) None of the above are possible.
D
The accompanying figure most closely represents speciation by ________.
(Selection favors hybrids in novel habitat not occupied by parental species)
A) natural selection
B) reinforcement
C) hybridization
D) polyploidy
C
From an ecological perspective, the dispersal of fruit flies (Drosophila) on the Hawaiian islands, which has resulted in speciation, is BEST termed ________.
A) vicariance
B) reinforcement
C) hybridization
D) adaptive radiation
Vicariance
The classical hypothesis of speciation is comprised of a three-step process. What are the three steps?
1. Isolation of populations
2. Divergence in traits
3. Reproductive isolation.
The model of speciation that hinges on a physical barrier preventing gene flow is ________ speciation.
Allopatric
Speciation events that occur when the geographic ranges of the populations involved overlap are termed ________.
Sympatric
Species divergence due to mating behavior and sexual selection, as has been documented in the Hawaiian crickets, is termed ________. [two words]
Assortative mating
The species concept based on careful analysis of the anatomical details of the specimen in
question is ________.
A) the morphospecies concept
B) the phylogenetic species concept
C) the biological species concept
D) the ecological species concept
A
The species concept based on analysis of character states that indicate the smallest
monophyletic group is ________.
A) the morphospecies concept
B) the phylogenetic species concept
C) the biological species concept
D) the ecological species concept
B
The species concept defined as a group of organisms that are capable of interbreeding to
produce fertile offspring is ________.
A) the morphospecies concept
B) the phylogenetic species concept
C) the biological species concept
D) the ecological species concept
C
Groups of organisms that cannot be distinguished morphologically but have no gene flow
between them, and are indeed evolutionary independent units, are known as ________ species.
Cryptic
Geographic isolation of populations can generally come about in two ways. What are they?
1. Dispersal
2. Vicariance
Relative to chromosome numbers, hybridization can produce speciation in two ways. What are they?
1. Polypoloidy Hybrid Speciation
2. Homoploid Hybrid Speciation
Selection that reduces the frequency of hybridization and/or the fitness of hybrids between
populations following secondary contact is termed ________.
Reinforcement
Morphospecies
Criterion: Quantifiable phenotypic differences

Advantage: Widely Applicable
•Fossils, asexual species, allopatric species, can take advantage of museum specimens

Disadvantages: May not accurately reflect evolution history
•Cryptic species: phenotypically indistinguishable, evolutionarily distinct
•Locally adapted populations: phenotypical distinct but no evolutionarily independent
•Can be highly subjective
Reproductive Isolation Mechanism
(Hybridization barriers) are a collection of mechanisms, behaviors & physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced are sterile
Evolutionary Significant Unit
Species is the smalles
Secondary Contact
•The third step in speciation is the reestablishment
of contact between sister
populations after they have diverged
Reinforcement
Secondary contact may lead to selection for increased reproductive isolation
Hybridization
Secondary contact may lead to hybridization & the fusion of divergent, sister populations
Hybrid Zones
The fitness of hybrids affects the width of hybrid zone and its fate
Allopatric Speciation
Physical isolation as a barrier to gene flow
Two Types of Allopatric Speciation
1. Dispersal: Colonization of new habitat (island)

2. Vicariance: Existing range is split by new barrier (Mountain range, habitat loss)
Vicariance
Existing range is split by new barrier (Mountain range, habitat loss)
Prezygotic isolation mechanisms:
•Habitat
•Behavioral
•Temporal
•Mechanical
•Gametic
Postzygotic isolation mechanisms:
•Hybrid viability
•Hybrid fertility
•Hybrid Breakdown
Adaptive Radiation
A process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches
Phylogenetic Species Concept
Criterion: Monophyly, time is a factor

Species are defined as monophyletic groups: evolutionary lineages that contain all known descendants of a single common ancestor

Species are united by shared derived characters (morphological & or molecular)

Advantages: Widely applicable & evolutionarily explicit
•Can be applied to fossils, asexual species, allopatric species
•Can be used to test alternative evolutionary hypothesis

Disadvantages:
•Different characters can give different answers: molecular and morphological data often disagree; different genes and different parts of the genome evolve at different rates
•May not work for young species: independent evolution by not enough time for monophyly
•Can inflate the number of species
Biological Species Concept
Criterion: reproductive isolation

Species are populations or groups of populations, within and among which individuals potentially interbreed and outside of which they do not breed

Advantages: evolutionarily and (potentially!) ecologically meaningful
• No interbreeding = no gene flow
• Less subjective than other species concepts: species that have the opportunity to exchange alleles but do not are self-defining

Disadvantages:
• Not applicable to asexual species or extinct species
• Hard to apply to many sexually reproducing extant species
Speciation 3 Step Process (Mechanism of Isolation)
1. Initial isolation: causes reduction or elimination of gene flow

2. Divergence in traits due to mutation, drift, natural selection, sexual selection (any or all)

3. Reproductive isolation
Traditional View
Initial isolation & divergence in traits happens in geographic isolation (allopatry)

Reproductive isolation happens upon secondary contact
Mechanism of Speciation
1. Reduction of gene flow: isolation

2. Start of evolutionary independence: Divergence in traits

3. Speciation per se: final reproductive isolation
Physical Isolation as a barrier to gene flow
Allopatric Speciation
What is Species?
•Evolution consists of changes in allele frequencies within populations (mutation, selection, migration, drift)

•A species is comprised of populations that can exchange alleles (gene flow/migration)

•Species are evolutionarily independent units that no longer exchange alleles

•Thus, the essence of speciation (formation of new species) is the lack of gene flow
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