BIO 315 EXAM 4 QUESTIONS AND
ANSWERS
Though Species Concepts differ somewhat in their assumptions they generally agree on
the following three main points: - Correct Answers -1. Species consist of groups of
interbreeding individuals
that share a common ancestry.
2. Species are a fundamental unit of evolution.
3. Species are evolutionarily independent units.
- Different species follow different evolutionary trajectories through time.
The Morphospecies Concept - Correct Answers -Species defined on the basis of
measurable
morphological differences.
problems with morphospecies concept - Correct Answers -• Differences used to classify
species can be arbitrary and may vary among scientists.
• As in extant organisms, morphology can be affected by the environment as well as
genetics (recall that VP = VG + VE).
what did Experiments by Clausen, Keck, and Hiesey (1948)
• Genetically identical cuttings of the same individual
Achillea plant grown at different altitudes prove? - Correct Answers -Quantitative Traits
are Influenced by
the Environment as well as Genotype
The Phylogenetic Species Concept - Correct Answers -Species are defined as the
smallest diagnosable monophyletic group, This species concept stresses the
importance of common ancestry between populations.
problems with Phylogenetic species concept - Correct Answers -• Good, well detailed
phylogenies are not well established for most organismal groups.
• Species-specific, diagnostic traits can be interpreted differently by different scientists.
- For example, is a single third position silent substitution at the DNA level a sufficient
diagnostic difference to define a species. How about 1% differentiation or 10%?
How do we establish non-arbitrary criteria in such cases?
The Biological Species Concept - Correct Answers -Popularized by the famous
evolutionary biologist, Ernst Mayr.
⇒ Populations of species that do not hybridize, or fail to produce fertile offspring
when they do, are then reproductively isolated and considered to be good species.
,This species concept stresses the importance of reproductive isolation between
populations.
problems with biological species concept - Correct Answers -• Reproductive isolation
can't be tested on fossil species.
• This concept doesn't apply to asexual species.
• This concept has difficulties with hybridizing species, e.g., many plants that exist
as ecologically and morphologically distinct species throughout their ranges but
may hybridize where they are sympatric (co-occur).
Cryptic Species in Marine Plankton:
The morphospecies are defined on how their cells overlap, but the differences are
subtle
and there was some question as to whether they are really separate species.
Amato et al. addressed this question using multiple species concepts,
• To apply the morphospecies concept they used light and transmission microscopy.
• To apply the phylogenetic concept they constructed a phylogeny from DNA
sequences.
• To apply the biological concept they conducted breeding experiments. - Correct
Answers -• Under the three separate
species concepts, the two
historical morphospecies
turn out to contain eight
different species in total!
• That is, regardless of the
concept used, the result
was the same.
• Such studies often reveal
that species diversity is
greater than previously
thought.
Speciation is a three-step process: - Correct Answers -1. The isolation of populations
via a barrier to gene flow
between populations.
• The barrier may be geographical, ecological,
biological, or a combination.
2. Genetic and ecological divergence.
• May arise as a function of natural selection as well
as genetic drift and mutation.
3. Reproductive isolation.
• Populations fail to hybridize in nature, or fail to
produce fertile offspring when they do hybridize.
allopatric speciation - Correct Answers -Speciation as a result of spatial
isolation
, Speciation may be successful... - Correct Answers -• If the groups had diverged enough
in allopatry they might not recognize
one another as members of the same species and, as a result, when later
coming into contact they would not interbreed (prezygotic reproductive
isolation) or, if they mate, fail to produce viable or reproductively
successful offspring (postzygotic reproductive isolation).
• In this case, the populations would have speciated and when the two
diverged populations come back into contact (into sympatry), they will
coexist without merging back together into a single species.
under what conditions will this mode of speciation fail? - Correct Answers -• If the two
populations come back into contact (into sympatry) before
they have diverged sufficiently in allopatry they may not be completely
reproductively isolated.
• In this case they might recognize each other as conspecifics, interbreed,
and their offspring develop well enough to foster gene flow between the
populations.
• The two populations would then merge back into a single continuous
population and speciation would have failed to occur.
Geographic isolation can
come about by two
mechanisms: - Correct Answers -1. Dispersal across a physical
barrier followed by
colonization of new habitat.
2. Vicariance, in which an
existing species range is
split by the appearance of a
new physical barrier to
gene flow (migration).
adaptive radiation - Correct Answers -The differentiation
of a single species
into many
descendent species
Geographic Isolation through Vicariance - Correct Answers -Vicariance events split a
species' distribution into two or more isolated ranges and
discourage or prevent gene flow between them. Such barriers may lead to speciation.
Evidence of Geographic Isolation through Vicariance - Correct Answers -Diversification
in Central American snapping
shrimp
Knowlton et al. Central American snapping
ANSWERS
Though Species Concepts differ somewhat in their assumptions they generally agree on
the following three main points: - Correct Answers -1. Species consist of groups of
interbreeding individuals
that share a common ancestry.
2. Species are a fundamental unit of evolution.
3. Species are evolutionarily independent units.
- Different species follow different evolutionary trajectories through time.
The Morphospecies Concept - Correct Answers -Species defined on the basis of
measurable
morphological differences.
problems with morphospecies concept - Correct Answers -• Differences used to classify
species can be arbitrary and may vary among scientists.
• As in extant organisms, morphology can be affected by the environment as well as
genetics (recall that VP = VG + VE).
what did Experiments by Clausen, Keck, and Hiesey (1948)
• Genetically identical cuttings of the same individual
Achillea plant grown at different altitudes prove? - Correct Answers -Quantitative Traits
are Influenced by
the Environment as well as Genotype
The Phylogenetic Species Concept - Correct Answers -Species are defined as the
smallest diagnosable monophyletic group, This species concept stresses the
importance of common ancestry between populations.
problems with Phylogenetic species concept - Correct Answers -• Good, well detailed
phylogenies are not well established for most organismal groups.
• Species-specific, diagnostic traits can be interpreted differently by different scientists.
- For example, is a single third position silent substitution at the DNA level a sufficient
diagnostic difference to define a species. How about 1% differentiation or 10%?
How do we establish non-arbitrary criteria in such cases?
The Biological Species Concept - Correct Answers -Popularized by the famous
evolutionary biologist, Ernst Mayr.
⇒ Populations of species that do not hybridize, or fail to produce fertile offspring
when they do, are then reproductively isolated and considered to be good species.
,This species concept stresses the importance of reproductive isolation between
populations.
problems with biological species concept - Correct Answers -• Reproductive isolation
can't be tested on fossil species.
• This concept doesn't apply to asexual species.
• This concept has difficulties with hybridizing species, e.g., many plants that exist
as ecologically and morphologically distinct species throughout their ranges but
may hybridize where they are sympatric (co-occur).
Cryptic Species in Marine Plankton:
The morphospecies are defined on how their cells overlap, but the differences are
subtle
and there was some question as to whether they are really separate species.
Amato et al. addressed this question using multiple species concepts,
• To apply the morphospecies concept they used light and transmission microscopy.
• To apply the phylogenetic concept they constructed a phylogeny from DNA
sequences.
• To apply the biological concept they conducted breeding experiments. - Correct
Answers -• Under the three separate
species concepts, the two
historical morphospecies
turn out to contain eight
different species in total!
• That is, regardless of the
concept used, the result
was the same.
• Such studies often reveal
that species diversity is
greater than previously
thought.
Speciation is a three-step process: - Correct Answers -1. The isolation of populations
via a barrier to gene flow
between populations.
• The barrier may be geographical, ecological,
biological, or a combination.
2. Genetic and ecological divergence.
• May arise as a function of natural selection as well
as genetic drift and mutation.
3. Reproductive isolation.
• Populations fail to hybridize in nature, or fail to
produce fertile offspring when they do hybridize.
allopatric speciation - Correct Answers -Speciation as a result of spatial
isolation
, Speciation may be successful... - Correct Answers -• If the groups had diverged enough
in allopatry they might not recognize
one another as members of the same species and, as a result, when later
coming into contact they would not interbreed (prezygotic reproductive
isolation) or, if they mate, fail to produce viable or reproductively
successful offspring (postzygotic reproductive isolation).
• In this case, the populations would have speciated and when the two
diverged populations come back into contact (into sympatry), they will
coexist without merging back together into a single species.
under what conditions will this mode of speciation fail? - Correct Answers -• If the two
populations come back into contact (into sympatry) before
they have diverged sufficiently in allopatry they may not be completely
reproductively isolated.
• In this case they might recognize each other as conspecifics, interbreed,
and their offspring develop well enough to foster gene flow between the
populations.
• The two populations would then merge back into a single continuous
population and speciation would have failed to occur.
Geographic isolation can
come about by two
mechanisms: - Correct Answers -1. Dispersal across a physical
barrier followed by
colonization of new habitat.
2. Vicariance, in which an
existing species range is
split by the appearance of a
new physical barrier to
gene flow (migration).
adaptive radiation - Correct Answers -The differentiation
of a single species
into many
descendent species
Geographic Isolation through Vicariance - Correct Answers -Vicariance events split a
species' distribution into two or more isolated ranges and
discourage or prevent gene flow between them. Such barriers may lead to speciation.
Evidence of Geographic Isolation through Vicariance - Correct Answers -Diversification
in Central American snapping
shrimp
Knowlton et al. Central American snapping
