Download Evolution of Populations

Chapter 23
The Evolution of Populations
Chapter 23
The Evolution of Populations
Modern evolutionary theory is a
synthesis of Darwinian selection and
Mendelian inheritance.
Evolution happens to populations
.
A population is defined by its gene
pool.
Chapter 23
The Evolution of Populations
The Hardy-Weinberg Theorem
The frequencies of alleles in the
population will remain constant if
Mendelian segregation is the only
process that affects the gene pool.
Chapter 23
The Evolution of Populations
The Hardy-Weinberg Equation
2
p
+ 2pq +
2
q
=1
Chapter 23
The Evolution of Populations
The Hardy-Weinberg Equation
p q
p pp pq
q pq qq
Chapter 23
The Evolution of Populations
2
p
+ 2pq +
2
q
p q
p pp pq
q pq qq
=1
Chapter 23
The Evolution of Populations
2
p
+ 2pq +
2
q
p q
p pp pq
q pq qq
=1
Chapter 23
The Evolution of Populations
2
p
+ 2pq +
2
q
p q
p pp pq
q pq qq
=1
Chapter 23
The Evolution of Populations
2
p
+ 2pq +
2
q
p q
p pp pq
q pq qq
=1
Chapter 23
The Evolution of Populations
2
p
+ 2pq +
2
q
p q
p pp pq
q pq qq
=1
Chapter 23
The Evolution of Populations
Hardy-Weinberg Equilibrium
•Very large population
•Totally isolated
•No mutations
•Random mating
•Equal reproductive success
Chapter 23
The Evolution of Populations
Microevolution
•Very large population
•Totally isolated
•No mutations
•Random mating
•Equal reproductive success
Chapter 23
The Evolution of Populations
Microevolution
•Genetic drift
•Totally isolated
•No mutations
•Random mating
•Equal reproductive success
Chapter 23
The Evolution of Populations
Microevolution
•Genetic drift
•Migration
•No mutations
•Random mating
•Equal reproductive success
Chapter 23
The Evolution of Populations
Microevolution
•Genetic drift
•Migration
•Mutations
•Random mating
•Equal reproductive success
Chapter 23
The Evolution of Populations
Microevolution
•Genetic drift
•Migration
•Mutation
•Natural selection and
sexual selection
Chapter 23
The Evolution of Populations
Microevolution
Generation-to-generation
change in allele frequencies.
Chapter 23
The Evolution of Populations
Genetic variation
Chapter 23
The Evolution of Populations
Genetic variation
Within populations and
between populations.
Chapter 23
The Evolution of Populations
Genetic variation
Produced by:
•Mutations
•Sexual recombination
Chapter 23
The Evolution of Populations
Genetic variation
Preserved by:
•Diploidy
•Balanced polymorphism
–Heterozygote advantage
–Frequency-dependent selection
Chapter 23
The Evolution of Populations
Fitness
Chapter 23
The Evolution of Populations
Fitness
The relative contribution an
individual makes to the next
generation’s gene pool.
Chapter 23
The Evolution of Populations
Fitness
Selection favors genotypes by
acting on phenotypes.
Chapter 23
The Evolution of Populations
Kinds of selection
•Directional
•Stabilizing
•Diversifying
Chapter 23
The Evolution of Populations
Disadvantages of
sexual reproduction:
•Only half the population can
give birth.
•Only half the offspring can
give birth.
Chapter 23
The Evolution of Populations
Advantages of
sexual reproduction:
•Genetic variation provides
resistance to disease.
•This is enough to overcome
the disadvantages.
Chapter 23
The Evolution of Populations
Sexual selection leads to
sexual dimorphism.
•Intrasexual selection:
competition between members of
same sex.
•Intersexual selection:
Choosiness for mates.
Chapter 23
The Evolution of Populations
Evolution has its limits.
1. Evolution builds on existing
structures.
2. Adaptations are compromises.
3. Chance is a powerful force.
4. Existing alleles can be favored,
but new ones cannot be made on
demand.