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17.1 Genes and Variation
2. Mendel’s work helped support evolution.
3. Variation is how natural selection
happens.
3. Variation comes from mutations.
2. Genotype: combination of alleles (Aa)
2. Phenotype: Genotype + Environment
3. Epigenetics – Environments role
2. Population: group of individuals from a
same species.
3. Gene Pool: all genes and alleles in a
population
3. Allele frequency: # of times an allele
occurs in a gene pool compared to total #
of alleles in the pool for the same gene.
(shown as a %)
4. Change in allele frequency =
evolution
Black (B) = 20 (40%)
BB = 16%
Brown (b) = 30 (60%)
Bb = 48%
bb = 36%
2.
Populations evolve,
not individuals
2. Mutations
3. Change in genetic material
3. Most neutral
2. Sexual Reproduction (Genetic Recombination)
3. Independent Assortment
3. Crossing Over
2. Lateral Gene Transfer
3. Can occur between same or different
species of single-celled organisms.
3. “pick up genes”
2. single-gene trait = controlled by only one gene
3. only 1-2 phenotypes
2. polygenic traits = traits controlled by 2 or more
genes
Evolution as Genetic Change in
Populations
2. Fitness: passing on alleles.
2. Single-gene allele frequencies change,
phenotype changes.
black color = absorb more light, heat up faster on
colder days, move faster.
Why would red be less common?
2. Polygenic traits produce shift in fitness.
3. Directional selection
4. Individuals on end of curve
more fit than those in
middle or
other end
3. Stabilizing Selection
4. Individuals near center of
curve
more fit.
4. Bell curve narrows.
3. Disruptive Selection
4. Individuals on outer end of curve are most
fit.
4. Two distinct phenotypes may form.
2. Series of chance occurrences can cause
an allele to become more or less common
in a population.
3. Faster if population is small
3. Genetic Drift: random change in
allele frequency.
2. Disasters may kill many individuals.
3. Rapid change in allele frequency.
3. Bottleneck Effect: change in allele
frequency after reduction in
population.
2. Few inhabitants move to a new habitat.
3. Different alleles than main
population.
3. Founders Effect: Allele frequency
change because of migration of small
subgroup.
Polydactyly – more common in American Amish
2. Genetic Equilibrium: allele
frequencies do not change in a population.
3. No evolution
Can sexually reproducing organisms be in
genetic equilibrium?
Yes. Meiosis and fertilization shuffles.
Does not change frequency.
2. Allele frequencies should remain
constant unless a factor causes it to
change.
Frequency of AA + Frequency of Aa + Frequency of aa = 100
2. Five factors that disrupt genetic
equilibrium:
3. Nonrandom mating
3. Small Population
3. Immigration or Emigration
3. Mutations
3. Natural Selection
*If one or more of these is happening,
evolution is happening*
The Process of Speciation
Turn to page 494 and define these terms.
1. Species
2. Speciation
3. Reproductive Isolation
4. Behavioral isolation
5. Geographic Isolation
6. Temporal isolation
Each group must describe one of the
events that occurred for the speciation of
Darwin’s species. Class will then go around
to fill in the rest of the notes.
2. Founders Arrive
3.
3.
2. Geographic Isolation
3.
3.
2. Changes in Gene Pool
3.
3.
2. Behavioral Isolation
3.
3.
2. Competition and Continued Evolution
3.
3.