IB 150 Exam 3 Questions With Complete Solutions
In terms of population genetics, what do we call this event when
a few individuals colonize a new geographical area?
founder effect
what is a likely consequence of such an event on the genetic
composition of the island population compared to the mainland
population?
allele frequencies likely already differ between the island and
mainland population due to the founder effect from the get go
Explain in your own words why allele frequencies in the new
island population will now change independently from those of
the mainland population?
Suggest a hypothesis for why natural selection might favor traits
that keep 2 individuals from populations that had been
reproductively isolated for a long time from mating (pre zygotic
isolation) even if hybrid offspring technically would still be
possible if mating were to take place.
due to environmental differences..... over time the environment
might have not been as favorable for the current individuals as
compared to the ancestors
what happens when two populations meet again?
gene flow equalizes frequencies again
,divergence caused pre-zygotic and/or post-zygotic reproductive
barriers
sympatric speciation results from disruptive selection of
individuals that are better suited to 2 different niches present in
the same environment.
Bc intermediate phenotypes have lower fitness in either niche,
hybrids between the phenotypic extremes are selected against
Why do individuals that have a tendency to assortativly mate
with individuals of like phenotype have higher fitness than
individuals that do not?
bc individuals that do not will likely have offspring of
intermediate phenotypes that htemselves will have reduced
fitness compared to their 2 parents
How would you suggest going about figuring out how closely
related 2 species are-how recently they diverged and become
different species?
using cladistics- shared traits represent the evolutionary history
and ancestral history.
=the more shared traits= the more common ancestors they share
What is a trait or a character?
a feature of an organisms that can be used to describe and
classify it
which of the following descriptions refers to which type of
trait/character?
,shared derived trait:
shared ancestral trait:
shared derived trait : a trait that evolved in the most recent
common ancestor of all members of this clade, no species
outside this clade possesses it , so it defines the clade currently
being considered
shared ancestral trait: a trait shared by members of a particular
clade and related species beyond the clade currently considered
analogous character:
a character that evolved independently via convergent evolution
into two unrelated lineages that make them appear more closely
related than they actually are
homologous character:
a character that is shared by a group of organisms bc its evolved
in the most recent common ancestor of that grouping of
organisms and signifies true relatedness bw them
Why are DNA sequences (or amino acid sequences encoded in
genes) such powerful characters for use in cladistics?
bc each nucleotide in the sequence is a separate character,
yielding millions of characters
, the sheer quantity of identifiable characters using genetic data
make it a very powerful source of characters to use for cladistics
Differentiate between different sources of diversity among
individuals in a population
Heritable variation:
Evolution: change in heritable traits
--->Evolution only applies to heritable traits- specifically to
changes in allele frequency of different alleles of a given gene
associated with such a heritable trait over time or between
generations
Variation due to genetics
Different alleles for one gene
Environmentally induced variation due to phenotypic plasticity
-->Variation due to different environments = develop in certain
way
-->Developmental plasticity- the same genotype can give rise to
different phenotypes, depending on environmental cues that alter
developmental gene regulation
identify variation that is of evolutionary significance
only when it is variation in heritable traits
define biological evolution with respect to allele frequencies
microevolution= the changes in the freq (and abundance) of
different alleles of a gene in a pop over time
In terms of population genetics, what do we call this event when
a few individuals colonize a new geographical area?
founder effect
what is a likely consequence of such an event on the genetic
composition of the island population compared to the mainland
population?
allele frequencies likely already differ between the island and
mainland population due to the founder effect from the get go
Explain in your own words why allele frequencies in the new
island population will now change independently from those of
the mainland population?
Suggest a hypothesis for why natural selection might favor traits
that keep 2 individuals from populations that had been
reproductively isolated for a long time from mating (pre zygotic
isolation) even if hybrid offspring technically would still be
possible if mating were to take place.
due to environmental differences..... over time the environment
might have not been as favorable for the current individuals as
compared to the ancestors
what happens when two populations meet again?
gene flow equalizes frequencies again
,divergence caused pre-zygotic and/or post-zygotic reproductive
barriers
sympatric speciation results from disruptive selection of
individuals that are better suited to 2 different niches present in
the same environment.
Bc intermediate phenotypes have lower fitness in either niche,
hybrids between the phenotypic extremes are selected against
Why do individuals that have a tendency to assortativly mate
with individuals of like phenotype have higher fitness than
individuals that do not?
bc individuals that do not will likely have offspring of
intermediate phenotypes that htemselves will have reduced
fitness compared to their 2 parents
How would you suggest going about figuring out how closely
related 2 species are-how recently they diverged and become
different species?
using cladistics- shared traits represent the evolutionary history
and ancestral history.
=the more shared traits= the more common ancestors they share
What is a trait or a character?
a feature of an organisms that can be used to describe and
classify it
which of the following descriptions refers to which type of
trait/character?
,shared derived trait:
shared ancestral trait:
shared derived trait : a trait that evolved in the most recent
common ancestor of all members of this clade, no species
outside this clade possesses it , so it defines the clade currently
being considered
shared ancestral trait: a trait shared by members of a particular
clade and related species beyond the clade currently considered
analogous character:
a character that evolved independently via convergent evolution
into two unrelated lineages that make them appear more closely
related than they actually are
homologous character:
a character that is shared by a group of organisms bc its evolved
in the most recent common ancestor of that grouping of
organisms and signifies true relatedness bw them
Why are DNA sequences (or amino acid sequences encoded in
genes) such powerful characters for use in cladistics?
bc each nucleotide in the sequence is a separate character,
yielding millions of characters
, the sheer quantity of identifiable characters using genetic data
make it a very powerful source of characters to use for cladistics
Differentiate between different sources of diversity among
individuals in a population
Heritable variation:
Evolution: change in heritable traits
--->Evolution only applies to heritable traits- specifically to
changes in allele frequency of different alleles of a given gene
associated with such a heritable trait over time or between
generations
Variation due to genetics
Different alleles for one gene
Environmentally induced variation due to phenotypic plasticity
-->Variation due to different environments = develop in certain
way
-->Developmental plasticity- the same genotype can give rise to
different phenotypes, depending on environmental cues that alter
developmental gene regulation
identify variation that is of evolutionary significance
only when it is variation in heritable traits
define biological evolution with respect to allele frequencies
microevolution= the changes in the freq (and abundance) of
different alleles of a gene in a pop over time
