The Process of
Evolution
How it Works and How we
See It
Topic Outline
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Evolution in a Genetic Context
- Microevolution
Hardy-Weinberg
Causes of Microevolution
Natural Selection
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Types of Selection
Maintenance of Variations
Speciation
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Modes of Speciation
Background Vocabulary
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Gene
Allele
Phenotype vs Genotype
Homozygous
Heterozygous
Gene pool
Microevolution
Polygenic (Quantitative) vs Monogenic Traits
The Hardy-Weinberg Model
2
p
+ 2pq +
And
p+q=1
2
q
What Does it Mean?
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p=Frequency of Dominant allele
q=Frequency of recessive allele
p2=frequency of Homozygous dominant
individuals
q2=frequency of homozygous recessive
indviduals
2pq=frequency of heterozygotes
So What?
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The Hardy-Weinberg principle states an
equilibrium of allele frequencies in a gene
pool of a sexually reproducing population,
p2 + 2pq + q2, won’t change as long as
certain conditions are met. What are these
conditions?
Example: Industrial Melanism
Causes of Microevolution
 Genetic
Mutations
 Gene Flow
 Nonrandom Mating
 Genetic Drift
 Natural Selection
MUTATIONS
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Gene mutations -- -- the only source of
new alleles
Chromosomal mutations -- -- alterations in
the number, composition, or the
arrangement of gene’s on a chromosome
Chromosomal mutations
Deletion
Translocation
Duplication
Inversion
Gene Flow
Physical Movement of Alleles
Nonrandom Mating
Assortative mating
Sexual selection
Genetic Drift
 Bottleneck
 Founder
Effect
Effect
Bottleneck Effect
Founder Effect
Founder Effect 2
Natural Selection
Types of Selection
 Directional
Selection
 Stabilizing
Selection
 Disruptive
Selection
Directional Selection
Stabilizing Selection
Disruptive Selection
Maintenance of Variations
Are there any advantages to variation in a
population?
Sickle Cell Distribution
Speciation
 Species
Definition
Morphological
Biological
Reproductive Isolation
Phylogenetic
Species
A
group of interbreeding
populations that share a gene
pool and are reproductively
isolated from other species.
 Subpopulations can exchange
genes. Different species can’t.
Reproductive Isolating Mechanisms
Prezygotic Isolating Mechanisms
Postzygotic Isolating Mechanisms
Modes of Speciation
 Allopatric
Speciation-spatial
separation
 Sympatric
Speciation- no
spatial separation
SYMPATRIC SPECIATION --EX
SPECIES A: 2N=14,
N = 7
DUPLICATION
SPECIES A’: 2N=28
N = 14
SPECIES A X SPECIES B 2N=21
N=?
Adaptive Radiation
Review
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Evolution in a Genetic Context
- Microevolution
Hardy-Weinberg
Causes of Microevolution
Natural Selection



Types of Selection
Maintenance of Variations
Speciation

Modes of Speciation