EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
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Biological Species Concept - CORRECT ANSWERS (Mayr)
Delimits species based on populations capable of interbreeding.
-gene flow defines the 'evolutionary fate'.
-morphology only may delineate species (are all things with wings birds?).
...But what about extinct species?
---What if matings are rare (mountains, highway, etc.)?
...What if hybrid species are not sterile but merely have reduced viability or fertility?
...Asexual organisms?
Phylogenetic Species Concept - CORRECT ANSWERS Delimits species by resolving the
smallest monophyletic clade with members uniquely sharing the derived traits.
-inherent taxonomic hierarchy.
-distinct evolutionary histories imply lack of gene flow.
...selection of traits for phylogenetic inference is important.
...contemporary species delimitations may change if unanticipated gene flow occurs.
Modes of Speciation: Allopatric Speciation - CORRECT ANSWERS Reproductive
incompatibility occurs in physically separated populations.
-genetic drift, accumulation of mutations and natural selection cause populations to diverse as
different alleles are fixed within them.
Prohibition of gene flow interferes with a common evolutionary fate, resulting in a new species.
,EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Two Models:
Dumbbell Model--Geographic barrier creates isolation.
Peripheral Isolate Model--Dispersal creates isolation.
trans-isthmus interactions were more aggressive and resulted in lower fitness.
-black spruce (BS) spread more broadly than red spruce (RS).
-mtDNA haplotypes in RS were a subset of those found in BS.
-RS has lower genetic diversity.
Modes of Speciation: Parapatric Speciation - CORRECT ANSWERS A gradient or cline
causes adjacent populations to experience different selective conditions.
-but the populations can still mate, generating hybrids.
Hybrids may lack traits that facilitate success in any part of the cline, causing them to be
outcompeted by nonhybrids.
Bounded hybrid superiority suggests that hybrids occupying the HZ harbor unique traits
exclusive of the progenitors that make them well-suited to environmental conditions not found
in either extreme of the cline.
Modes of Speciation: Sympatric Speciation - CORRECT ANSWERS Speciation in the
absence of physical or spatial barriers.
,EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Two genetically related cichlids arose in a small, young lake with no obvious barriers between
these species to prevent gene flow.
Diet appeared to drive the divergence as each species was well-adapted to their habitats and
preferred within-species mating, driving fixation of divergent alleles.
Apple (A) and hawthrone (H) trees exist sympatrically and apple maggot (AM) fly 'races' (A-AM
and H-AM) emerged ~140 years.
Sympatric speciation of apple maggot flies appears to be influenced by the different fruiting
times (3-4 wk/AM life span) of the host plants.
Reduced gene flow between sympatric AM on different host trees.
Niche Partitioning--selection drives speciation facilitating differential patterns of resource
usage.
Niche Conservatism--the degree to which species retain their ancestral ecological traits,
suggesting a genetic component to their behavior.
Facilitating Sympatric Speciation: Character Displacement - CORRECT ANSWERS Traits
emerge that reduce competition where co-occurring species exist.
Ecological character displacement: trait evolution stemming from selection to lessen resource
competition between species and therefore acts on traits associated with resource use (e.g.,
morphological structures such as beaks and jaws).
, EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Reproductive character displacement: divergent mating signals and morphological barriers to
successful mating events.
-minimize costly reproductive interactions
-hybrids with reduced fitness
Reproductive Isolation Mechanisms - CORRECT ANSWERS Prezygotic isolating
mechanisms prevent mating or successful fertilization between different, closely-related
species.
-behavioral (mating calls).
-temporal (divergent mating times).
-habitat (spatially isolated).
-physiological (incompatible mating physiology).
Postzygotic isolating mechanisms affect zygote/embryo survival.
-zygote doesn't survive
-sterile hybrids
-backcrosses or F2 hybrids are sterile
Haldane's dominance rule:
If hybrids have reduced fitness, then hybrids will be under strong negative selection in
heterogametic sexes.
XX XY X*X* X*Y
XX*--X-linked recessive/deleterious traits are masked by complementary chromosome.
X*Y--X-linked recessive/deleterious traits are not masked.
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Biological Species Concept - CORRECT ANSWERS (Mayr)
Delimits species based on populations capable of interbreeding.
-gene flow defines the 'evolutionary fate'.
-morphology only may delineate species (are all things with wings birds?).
...But what about extinct species?
---What if matings are rare (mountains, highway, etc.)?
...What if hybrid species are not sterile but merely have reduced viability or fertility?
...Asexual organisms?
Phylogenetic Species Concept - CORRECT ANSWERS Delimits species by resolving the
smallest monophyletic clade with members uniquely sharing the derived traits.
-inherent taxonomic hierarchy.
-distinct evolutionary histories imply lack of gene flow.
...selection of traits for phylogenetic inference is important.
...contemporary species delimitations may change if unanticipated gene flow occurs.
Modes of Speciation: Allopatric Speciation - CORRECT ANSWERS Reproductive
incompatibility occurs in physically separated populations.
-genetic drift, accumulation of mutations and natural selection cause populations to diverse as
different alleles are fixed within them.
Prohibition of gene flow interferes with a common evolutionary fate, resulting in a new species.
,EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Two Models:
Dumbbell Model--Geographic barrier creates isolation.
Peripheral Isolate Model--Dispersal creates isolation.
trans-isthmus interactions were more aggressive and resulted in lower fitness.
-black spruce (BS) spread more broadly than red spruce (RS).
-mtDNA haplotypes in RS were a subset of those found in BS.
-RS has lower genetic diversity.
Modes of Speciation: Parapatric Speciation - CORRECT ANSWERS A gradient or cline
causes adjacent populations to experience different selective conditions.
-but the populations can still mate, generating hybrids.
Hybrids may lack traits that facilitate success in any part of the cline, causing them to be
outcompeted by nonhybrids.
Bounded hybrid superiority suggests that hybrids occupying the HZ harbor unique traits
exclusive of the progenitors that make them well-suited to environmental conditions not found
in either extreme of the cline.
Modes of Speciation: Sympatric Speciation - CORRECT ANSWERS Speciation in the
absence of physical or spatial barriers.
,EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Two genetically related cichlids arose in a small, young lake with no obvious barriers between
these species to prevent gene flow.
Diet appeared to drive the divergence as each species was well-adapted to their habitats and
preferred within-species mating, driving fixation of divergent alleles.
Apple (A) and hawthrone (H) trees exist sympatrically and apple maggot (AM) fly 'races' (A-AM
and H-AM) emerged ~140 years.
Sympatric speciation of apple maggot flies appears to be influenced by the different fruiting
times (3-4 wk/AM life span) of the host plants.
Reduced gene flow between sympatric AM on different host trees.
Niche Partitioning--selection drives speciation facilitating differential patterns of resource
usage.
Niche Conservatism--the degree to which species retain their ancestral ecological traits,
suggesting a genetic component to their behavior.
Facilitating Sympatric Speciation: Character Displacement - CORRECT ANSWERS Traits
emerge that reduce competition where co-occurring species exist.
Ecological character displacement: trait evolution stemming from selection to lessen resource
competition between species and therefore acts on traits associated with resource use (e.g.,
morphological structures such as beaks and jaws).
, EEOB 3310 EXAM #2 QUESTIONS AND ANSWERS LATEST
DOWNLOADED 2025/2026 A COMPLETE SOLUTION ALL
ANSWERS CORRECT VERIFIED BEST GRADED TO SCORE A+ FOR
SUCCESS
Reproductive character displacement: divergent mating signals and morphological barriers to
successful mating events.
-minimize costly reproductive interactions
-hybrids with reduced fitness
Reproductive Isolation Mechanisms - CORRECT ANSWERS Prezygotic isolating
mechanisms prevent mating or successful fertilization between different, closely-related
species.
-behavioral (mating calls).
-temporal (divergent mating times).
-habitat (spatially isolated).
-physiological (incompatible mating physiology).
Postzygotic isolating mechanisms affect zygote/embryo survival.
-zygote doesn't survive
-sterile hybrids
-backcrosses or F2 hybrids are sterile
Haldane's dominance rule:
If hybrids have reduced fitness, then hybrids will be under strong negative selection in
heterogametic sexes.
XX XY X*X* X*Y
XX*--X-linked recessive/deleterious traits are masked by complementary chromosome.
X*Y--X-linked recessive/deleterious traits are not masked.
