Bio 206 Final Exam | Questions & Answers (100 %Score) Latest Updated 2024/2025
Comprehensive Questions A+ Graded Answers | With Expert Solutions
Homoplasy - A similar (analogous) structure or molecular sequence that has evolved
independently in two species.
Problems with Homoplasy - It can create an unpredictable gain or loss of a specific trait
over time and during the evolution of new species
Slowly evolving genes - Useful for distantly related species
Rapidly evolving species - useful for closely related species
Most useful traits - Shared derived traits
convergent evolution - repeated evolution of a trait
Homology - Similarity in characteristics resulting from a shared ancestry.
Synapomorphies - shared derived characteristics that evolved in a common ancestor of
the group and were inherited by all of its descendants
Evolution - change in allele frequencies through time
Population genetics - - tracks the fate, across generations, of alleles in populations
- concerned with whether a particular allele or genotype will become more or less
common over time, and WHY
single locus polymorphism - genes that control a single trait
additive ("incomplete dominance") - allele yields twice the phenotypic effect when 2
copies are present (phenotype is in-between)
5 Hardy Weinberg Assumptions - 1. No selection
2. No mutation
3. No migration
4. No chance events
5. There is random mating
Primary uses of HWE - - compute genotype frequencies from generation to generation
- null model in tests for evolution (compares observed to expected)
- forensic analysis
Common mistake of HWE - - Population is in HWE because it sums to 1, this is just to
check your math
,* To determine HWE you need to COMPARE observed to expected *
Genetic Drift - - A change in the allele frequency of a population as a result of chance
events rather than natural selection
- Alleles are "sampled" to form progeny
Finite Population - - Chance events
- Randomly pair egg and sperm to make zygotes. If population is finite in size, WILL
NOT GET allele frequencies in their exact proportions
Genetic Bottleneck - Non-representative set of alleles for subsequent populations, even
after the population size rebounds
Founder Effect - - Type of genetic bottleneck resulting from a small number of
individuals colonizing a new, isolated habitat
- Not representative of source population
Properties of genetic drift - - DIRECTION of change in allele frequency can NOT be
PREDICTED
- One allele will eventually be fixed, the other eliminated: genetic drift tends to REMOVE
VARIATION
- Probability that a particular allele will eventually be fixed (or lost) is proportional to its
frequency in the population
What does drift do to genetic diversity? (One word) - Reduces
3 main features of genetic drift - - loss of genetic variation results WITHIN populations
(1 allele will eventually be lost or fixed)
- Genetic divergence results BETWEEN populations (populations become more
different by chance)
- Drift CAUSES evolution, but NOT adaptive evolution
Fitness - expected reproductive success of an individual with a particular phenotype (or
genotype)
3 components of fitness - - survival to reproductive age
- mating success
- fecundity
Absolute fitness equation - (probability of survival) * (average number of offspring)
Relative Fitness - Fitness of a genotype standardized by comparison to other genotypes
Change is fastest when the selection is _____________ (ie; larger differences in
relative fitness) and allele frequencies are ___________ - strong; similar
, Additive (relationships among alleles at a locus) - allele yields twice the phenotypic
effect when two copies present
Dominance - dominant allele masks presence of recessive in heterozygote
Directional Selection - 1 of the 2 alleles has higher fitness than the other one
Selection coefficient (s) - Fitness disadvantage to (or strength of selection against) a
genotype
s=1-w
Dominance Coefficient (h) - Proportion of s applied to the heterozygous genotype
hs = 1 - w
h = hs/s
Heterozygote advantage (overdominance) - - heterozygote has greater fitness than
either homozygote
- results in stable equilibrium polymorphism
Heterozygote Disadvantage (Underdominance) - - when a heterozygote has a lower
fitness than either homozygote
- results to unstable equilibrium polymorphism
Negative Frequency Dependent Selection - - An allele becomes LESS fit as it becomes
more common
- Multiple alleles will be maintained in a stable polymorphism (both alleles are
maintained), promotes genetic diversity
- Fitness is GREATEST when the phenotype is RARE
Ex; pathogen, mating, resource use, predation
Positive Frequency-dependent Selection - - An allele becomes MORE FIT as it
becomes MORE COMMON
- leads to unstable polymorphism (maintaining both alleles is unstable)
Consider the "A" locus with 2 alleles (A, a). Which one of the following sets of relative
fitness (w) will consistently lead to the highest equilibrium frequency of the "a" allele?
A. WAA = 1.00, WAa= 0.90, Waa = 0.80
B. WAA = 1.00, WAa= 0.87, Waa = 1.00
C. WAA = 0.01, WAa= 1.00, Waa = 0.10
D. WAA = 0.90, WAa= 1.00, Waa = 0.90 - C. WAA = 0.01, WAa= 1.00, Waa = 0.10
- You want to identify in which case are the "a" doing better than "A"
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