BIOL 201 Midterm: Exam 1 Review
Biology Exam Review
Section 1
Microevolution is a fact, macroevolution is a theory
!
Theory of special creation: life created by divine force; each species created separately
!
Homology: similarities in anatomical form despite differences in function
!
Law of Succession: species found in a particular area look like those in the area
previously
!
Section 2/3
Lamarckian evolution is the inheritance of acquired characteristics. It says individuals
change in response to changes in environment, more complex forms descend from
simpler ones; changes can be passed on to offspring.
Species evolve independently and in parallel
○
!
Darwin’s theory said species are descended from one another to form a branching tree
of life.
Through descent w modification and natural selection
Evolution happens to populations, natural selection happens to individuals
§
Natural Selection can only occur with variation, inheritance, and differential
reproductive success
§
○
!
Types of Change
Transformational: ensemble changes because each party changes
○
Variational: ensemble changes because something sorts among variants in
original ensemble
○
Ex: crushing vs sifting
Crushing would be transformational which is Lamarckian
§
Sifting would be Variational which is Darwinian
§
○
!
Common Misconceptions
Populations change traits because some are more successful than others
○
Changes in a population occur through selection of certain traits
○
The environment can indirectly cause change
○
Mutations are random
○
Offspring can inherit both pos and neg traits
○
Acquired characteristics are heritable
○
!
Section 4
Phylogeny: a model of the branching relationships of a population as they give rise to
descendant populations
Show varying observable traits
○
Branches represent populations evolving over time
○
Nodes represent points in time when populations diverge
○
The Most Recent Common Ancestor (MRCA) is the most recent node
○
A phylogeny is kind of a nested hierarchy of clades - a clade is a collection of
branches, internal nodes, and tips that include an MRCA and all of its
descendants - a monophyly
○
Paraphyletic groups don't contain all the descendants of the most recent
common ancestor
○
!
The Principle of Parsimony
The most parsimonious model is the one that requires the fewest # of evolutionary
changes in the traits under consideration
○
Ex:
Chimp Human
CATGCA CTTGGA
Answer: parsimony would lead us to infer that the sequence was CxTGyA
where x could be A or T and y could be C or G
Given an outgroup, you can use it to plug in what x and y would be
to reduce ambiguity
"
○
!
Homology vs Analogy
Homology is shared derived character
Similar structure, different function
§
○
Analogy is convergent evolution - evolves independently
Different structure, similar function
§
○
!
To figure out if something was passed from one person to another, you can look at the
phylogenetic tree and see if they had a MRCA.
!
Section 5
In the what used to be deemed true concept of blending inheritance, the most extreme
phenotypes, black/white, were progressively lost from the population until eventually, all
phenotypes were intermediate, gray.
!
Mendel’s 2 Laws are the Law of Segregation and the Law of Independent Assortment.
Law of Segregation: 2 alleles separate during gamete formation and end up in dif
gametes
○
Law of independent assortment: each pair of alleles separate independently of
others during gamete formation
○
!
Probability Review
Multiplication of 2 probabilities because independent (AND)
○
Addition of 2 probabilities bc mutually exclusive (OR)
○
!
Population Genetics describes the transmission of alleles in a population from 1 gen to
the next
!
Hardy-Weinberg Equilibrium (HWE) predicts the population genotype frequencies from
the allele frequencies
Assumptions:
No mutation
§
No migration
§
No selection
§
Random mating
§
Infinite population size
§
○
p = f(A) and q = f(a)
○
p + q = 1
○
f(AA) = p^2 and f(aa) = q^2
○
f(Aa) = 2pq
○
p^2 + 2pq + q^2 = 1
○
In a graph, AA would increase, aa would decrease, and Aa would increase and
then decrease
○
!
There are 4 types of equilibria:
Stable
○
Unstable
○
Neutral
○
Mixed
○
!
In an equilibrium:
it is reached in 1 gen of random mating
○
genotype frequencies will immediately return to same values if perturbed, allele
frequencies will not
○
!
Section 6
Fitness depends on survival and fecundity - fecundity is the ability to produce offspring
Fitness = Prob(survival to reproduction) x fecundity
○
!
s = selection coefficient and describes the fitness reduction of the one phenotype
relative to another
s = 1 - (reduced fit #)
○
!
After 1 generation, the genotype frequencies become p^2, 2pq, and q^2(1-s) - because
the recessive homozygous allele is the one with the decreased fitness.
The associated ALLELE frequency after one gen of selection with this would be
○
!
Section 7
The larger the value of s, the faster fixation occurs.
!
Evolution is fast only when selection is strong and variation is high
!
If there is no variation for selection, if either p or q is 0, then the allele that is 0 will not
move (on the graph)
!
Polymorphisms can never go to frequencies of 0 or 1 in an infinite population - they only
approach those limits asymptotically
!
True fixation happens in finite populations
!
In incomplete dominance, A1 reaches fixation most rapidly, when A1 is dominant over
A2, its initial increase is the most rapid but the pace slows back down once its in the
common population. When A1 is recessive it takes much longer to inc frequency
!
Rate of change is influenced by the degree of dominance
A recessive allele inc in frequency:
more slowly when rare
§
more quickly when common
§
○
A dominant allele inc
more quickly when rare
§
more slowly when common
§
○
!
Over-dominance is when there is heterozygote advantage
Genotype frequencies are p^2(1-s), 2pq, and q^2(1-t)
○
!
Selection that favors a particular allele will eventually remove genetic variation
!
Section 8
Random mutation results in high variance while the theory of acquired inherited
resistance results in low variance
!
Forward Backward Mutation
without selection
○
!
Mutation-Selection Balance (with selection)
Mutation–selection balance is an equilibrium in the number of deleterious alleles
in a population that occurs when the rate at which deleterious alleles are created
by mutation equals the rate at which deleterious alleles are eliminated
by selection.
!
!
A deleterious allele with a selective disadvantage would be present at a higher frequency
when it is recessive because it will be able to hide in the heterozygotes whereas if it was
dominant, it would be identifiable and an easy target because it would show clearly in
homozygote dominant and heterozygote form.
!
Section 9
Vertical transmission (mother to daughter) is lower virulence and lower phage titer
!
Horizontal transmission (to uninfected unrelated hosts) is higher virulence, higher phage
titer
!
The reason there is an arms race w bacteria is because they are able to so quickly
develop antibiotic resistance.
!
Exam%1%Review
#$%&'()*+, -./&%)&*, 0+,1203
0452,67
Biology Exam Review
Section 1
Microevolution is a fact, macroevolution is a theory
!
Theory of special creation: life created by divine force; each species created separately
!
Homology: similarities in anatomical form despite differences in function
!
Law of Succession: species found in a particular area look like those in the area
previously
!
Section 2/3
Lamarckian evolution is the inheritance of acquired characteristics. It says individuals
change in response to changes in environment, more complex forms descend from
simpler ones; changes can be passed on to offspring.
Species evolve independently and in parallel
○
!
Darwin’s theory said species are descended from one another to form a branching tree
of life.
Through descent w modification and natural selection
Evolution happens to populations, natural selection happens to individuals
§
Natural Selection can only occur with variation, inheritance, and differential
reproductive success
§
○
!
Types of Change
Transformational: ensemble changes because each party changes
○
Variational: ensemble changes because something sorts among variants in
original ensemble
○
Ex: crushing vs sifting
Crushing would be transformational which is Lamarckian
§
Sifting would be Variational which is Darwinian
§
○
!
Common Misconceptions
Populations change traits because some are more successful than others
○
Changes in a population occur through selection of certain traits
○
The environment can indirectly cause change
○
Mutations are random
○
Offspring can inherit both pos and neg traits
○
Acquired characteristics are heritable
○
!
Section 4
Phylogeny: a model of the branching relationships of a population as they give rise to
descendant populations
Show varying observable traits
○
Branches represent populations evolving over time
○
Nodes represent points in time when populations diverge
○
The Most Recent Common Ancestor (MRCA) is the most recent node
○
A phylogeny is kind of a nested hierarchy of clades - a clade is a collection of
branches, internal nodes, and tips that include an MRCA and all of its
descendants - a monophyly
○
Paraphyletic groups don't contain all the descendants of the most recent
common ancestor
○
!
The Principle of Parsimony
The most parsimonious model is the one that requires the fewest # of evolutionary
changes in the traits under consideration
○
Ex:
Chimp Human
CATGCA CTTGGA
Answer: parsimony would lead us to infer that the sequence was CxTGyA
where x could be A or T and y could be C or G
Given an outgroup, you can use it to plug in what x and y would be
to reduce ambiguity
"
○
!
Homology vs Analogy
Homology is shared derived character
Similar structure, different function
§
○
Analogy is convergent evolution - evolves independently
Different structure, similar function
§
○
!
To figure out if something was passed from one person to another, you can look at the
phylogenetic tree and see if they had a MRCA.
!
Section 5
In the what used to be deemed true concept of blending inheritance, the most extreme
phenotypes, black/white, were progressively lost from the population until eventually, all
phenotypes were intermediate, gray.
!
Mendel’s 2 Laws are the Law of Segregation and the Law of Independent Assortment.
Law of Segregation: 2 alleles separate during gamete formation and end up in dif
gametes
○
Law of independent assortment: each pair of alleles separate independently of
others during gamete formation
○
!
Probability Review
Multiplication of 2 probabilities because independent (AND)
○
Addition of 2 probabilities bc mutually exclusive (OR)
○
!
Population Genetics describes the transmission of alleles in a population from 1 gen to
the next
!
Hardy-Weinberg Equilibrium (HWE) predicts the population genotype frequencies from
the allele frequencies
Assumptions:
No mutation
§
No migration
§
No selection
§
Random mating
§
Infinite population size
§
○
p = f(A) and q = f(a)
○
p + q = 1
○
f(AA) = p^2 and f(aa) = q^2
○
f(Aa) = 2pq
○
p^2 + 2pq + q^2 = 1
○
In a graph, AA would increase, aa would decrease, and Aa would increase and
then decrease
○
!
There are 4 types of equilibria:
Stable
○
Unstable
○
Neutral
○
Mixed
○
!
In an equilibrium:
it is reached in 1 gen of random mating
○
genotype frequencies will immediately return to same values if perturbed, allele
frequencies will not
○
!
Section 6
Fitness depends on survival and fecundity - fecundity is the ability to produce offspring
Fitness = Prob(survival to reproduction) x fecundity
○
!
s = selection coefficient and describes the fitness reduction of the one phenotype
relative to another
s = 1 - (reduced fit #)
○
!
After 1 generation, the genotype frequencies become p^2, 2pq, and q^2(1-s) - because
the recessive homozygous allele is the one with the decreased fitness.
The associated ALLELE frequency after one gen of selection with this would be
○
!
Section 7
The larger the value of s, the faster fixation occurs.
!
Evolution is fast only when selection is strong and variation is high
!
If there is no variation for selection, if either p or q is 0, then the allele that is 0 will not
move (on the graph)
!
Polymorphisms can never go to frequencies of 0 or 1 in an infinite population - they only
approach those limits asymptotically
!
True fixation happens in finite populations
!
In incomplete dominance, A1 reaches fixation most rapidly, when A1 is dominant over
A2, its initial increase is the most rapid but the pace slows back down once its in the
common population. When A1 is recessive it takes much longer to inc frequency
!
Rate of change is influenced by the degree of dominance
A recessive allele inc in frequency:
more slowly when rare
§
more quickly when common
§
○
A dominant allele inc
more quickly when rare
§
more slowly when common
§
○
!
Over-dominance is when there is heterozygote advantage
Genotype frequencies are p^2(1-s), 2pq, and q^2(1-t)
○
!
Selection that favors a particular allele will eventually remove genetic variation
!
Section 8
Random mutation results in high variance while the theory of acquired inherited
resistance results in low variance
!
Forward Backward Mutation
without selection
○
!
Mutation-Selection Balance (with selection)
Mutation–selection balance is an equilibrium in the number of deleterious alleles
in a population that occurs when the rate at which deleterious alleles are created
by mutation equals the rate at which deleterious alleles are eliminated
by selection.
!
!
A deleterious allele with a selective disadvantage would be present at a higher frequency
when it is recessive because it will be able to hide in the heterozygotes whereas if it was
dominant, it would be identifiable and an easy target because it would show clearly in
homozygote dominant and heterozygote form.
!
Section 9
Vertical transmission (mother to daughter) is lower virulence and lower phage titer
!
Horizontal transmission (to uninfected unrelated hosts) is higher virulence, higher phage
titer
!
The reason there is an arms race w bacteria is because they are able to so quickly
develop antibiotic resistance.
!
Exam%1%Review
#$%&'()*+, -./&%)&*, 0+,1203 0452,67
Document Summary
Microevolution is a fact, macroevolution is a theory. Theory of special creation: life created by divine force; each species created separately. Homology: similarities in anatomical form despite differences in function. Law of succession: species found in a particular area look like those in the area previously. Lamarckian evolution is the inheritance of acquired characteristics. It says individuals change in response to changes in environment, more complex forms descend from simpler ones; changes can be passed on to offspring. Darwin"s theory said species are descended from one another to form a branching tree of life. Evolution happens to populations, natural selection happens to individuals. Natural selection can only occur with variation, inheritance, and differential reproductive success. Variational: ensemble changes because something sorts among variants in original ensemble. Populations change traits because some are more successful than others. Changes in a population occur through selection of certain traits. Offspring can inherit both pos and neg traits.
