EVOLUTION
DAY
REVIEW
DARWIN’S FOUR CRITERIA FOR
NATURAL SELECTION TO OCCUR
Overproduction of offspring leads to more offspring than
environment can support
Variation in those offspring
Variations are inherited
Offspring that are better adapted to environment leave subsequently
more offspring
Darwin also saw that when
humans choose organisms
with specific characteristics
as breeding stock, they are
performing the role of the
environment
– This is called artificial
selection
Adopt me!!
Figure 13.4A
The evolution of insecticide resistance is an example of natural
selection in action
Insecticide
application
Chromosome with gene
conferring resistance
to insecticide
Additional
applications of the
same insecticide will
be less effective, and
the frequency of
resistant insects in
the population
will grow
Survivor
Figure 13.5B
13.6 POPULATIONS ARE THE UNITS
OF EVOLUTION
A species is a group of populations whose
individuals can interbreed and produce
fertile offspring
A population is a group of interbreeding
individuals living in same place and same
time.
• Populations evolve, not individuals!!!
Figure 13.6
13.7 MICROEVOLUTION IS CHANGE
IN A POPULATION’S GENE POOL
OVER TIME
A gene pool is the total collection of genes in a population at any one
time
Microevolution is a change in the relative frequencies of alleles in a
gene pool
13.8 THE GENE POOL OF A
NONEVOLVING POPULATION
REMAINS CONSTANT OVER THE
GENERATIONS
Hardy-Weinberg equilibrium states that the
shuffling of genes during sexual
reproduction does not alter the proportions
of different alleles in a gene pool
• In other words, when the population is in
Hardy Weinberg equilibrium, the population
in NOT EVOLVING!!!!
• We often can use HW to estimate allele
frequencies in human populations!
Figure 13.8A
13.10 FIVE CONDITIONS ARE
REQUIRED FOR HARDYWEINBERG EQUILIBRIUM
The population is very large (no genetic drift)
The population is isolated (no emmigration or immigration)
Mutations do not alter the gene pool (no mutations)
Mating is random(no selective mating)
All individuals are equal in reproductive success (no natural
selection)
FIVE FINGERS OF EVOLUTION
(CAUSES OF MICROEVOLUTION)
• Small population size and Genetic Drift
• Non-random mating
•
Mutations
• Gene flow (migration)
• Natural selection
13.18 GENES PUT INTO FUTURE
GENERATIONS DEFINE
EVOLUTIONARY FITNESS
An individual’s fitness is the contribution it makes to the gene pool of
the next generation relative to the contribution made by other
individuals
Production of fertile offspring is the only score that counts in natural
selection
13.19 THERE ARE THREE GENERAL
Frequency of
individuals
OUTCOMES OF NATURAL SELECTION
Original
population
Phenotypes (fur color)
Original
population
Evolved
population
Stabilizing selection
Directional selection
Diversifying selection
Figure 13.19
The biological species concept defines a species as
– a population or group of populations whose
members can interbreed and produce fertile
offspring
The biological species concept is not to asexual organisms
• Most organisms are classified based on
observable phenotypes
– The morphological species concept
• The genealogical species concept defines a
species as a cluster of organisms representing a
specific evolutionary lineage
• The ecological species concept defines a species
by its ecological role
Hybrid sterility is one type of postzygotic barrier
– A horse and a
donkey may
produce a hybrid
offspring, a mule
– Mules are sterile
Figure 14.2C
MECHANISMS OF SPECIATION
14.3 GEOGRAPHIC ISOLATION CAN
LEAD TO SPECIATION
When a population is cut off from its parent stock, species evolution
may occur
• An isolated population may become genetically unique as its gene
pool is changed by natural selection, genetic drift, or mutation
• This is called allopatric speciation
Figure 14.3
Adaptive radiation on an island chain
1
A
Species A
from mainland
2
B
B
3
B
C
B
4
C
C D
C
C
D
5
Figure 14.4B
ADAPTIVE RADIATION
OF DINOSAURS