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 Also have out your natural selection reading
assignment from the weekend
 Gene flow
 Gene pool
 Genetic drift
Species
 a group of individual organisms that are
capable of interbreeding to produce fertile
offspring in nature.
Population
 A group of organisms of one species that
interbreed and live in the same place at the
same time
Common Ancestor
 An organism which is the shared ancestor of two
(or more) different descendant groups of
organisms.
•You will be able to describe Darwin’s theory of
natural selection as well as give examples that
support the theory.
•You will be able to describe the conditions
required for natural selection.
Misconceptions
 Humans did not evolve from apes, gorillas or
chimps. We are all modern species that have followed
different evolutionary paths, though humans share a
common ancestor with some primates, such as the
African ape
•Evolution: changes
that transform life
over an immense
time.
•Darwin published ,
The Origins of
Species making two
main points for the
mechanisms of
evolution…
1. Descent with
modification
2. Natural selection
Descent with Modification
 Species living today descended from ancestral species
 Species spread into various habitats over millions of
years
 Species accumulated different modifications, or
adaptations, to diverse ways of life as genes are passed on
 Results in diversity of species
Natural Selection
 Process by which individuals
with inherited characteristics
well-suited for their
environment leave more
offspring on average than do
other individuals
 Survival and reproduction of
the fittest
Theory of Natural Selection Flow
Chart
Population of
Organisms
Overproduction
Variation
Struggle for
existence
Differences in
reproductive success
Evolution of
adaptations
What have you learned?
 What are the two main points that Darwin made in is
book to ague the mechanisms of evolution?
 Descent with modification and natural selection
 What is natural selection?
 Process by which individuals with inherited
characteristics well-suited for their environment leave
more offspring on average than do other individuals
 Describe some conditions that could lead to a
struggle for existence among individuals in a
population.
 Over population, limited resources, changes occurring
in the environment
Evidence of Evolution
 The fossil record= shows patterns of evolution over
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millions of years
Comparative Anatomy
Comparative Embryology (Not on foldable)
Comparative Biochemistry: amino acid tables
Geographic Distribution: similar organisms separated
by land
Comparative Anatomy
 Homologous structures= anatomically similar
structures inherited from a common ancestor
Comparative Anatomy
 Analogous
structures=
Structures of
different species
having similar or
corresponding
function but not
from the same
evolutionary origin
Comparative anatomy
 Vestigial structures= Vestigial structures are body
parts that seemingly have no purpose or function.
Perhaps they once did, but somewhere along the way
they lost their functions and are now basically useless
Comparative Embryology
 Similar phases of development
Geographic distribution
Theory of Natural Selection Flow
Chart
Population of
Organisms
Overproduction
Variation
Struggle for
existence
Differences in
reproductive success
Evolution of
adaptations
You will be able to discuss mechanisms of
evolution other than natural selection
such as genetic drift and gene flow.
Gene Pool
Consists of all the
alleles in all the
individuals that
make up a
population.
The process of
meiosis (specifically
crossing over) and
fertilization shuffle
alleles in the gene
pool giving us
genetic diversity
Genetic Drift
 A change in the population due to chance
 All populations are subject to some genetic drift;
however, the smaller the population the greater the
impact.
 Bottleneck effect- disasters can reduce the size
of a population. By chance some alleles are
represented more than others while others are
completely eliminated
 Founder effect- when a few individuals colonize
an isolated habitat. There is low genetic makeup
Bottleneck effect
Founder Effect
Demonstration for Genetic Drift
 Hypothesis:
 What would the populations look like generations
from now if there were no environmental changes
and the gene pool remained the same?
 Analysis:
 What are some deadly “chance” events?
 How did the removal of some of the marbles
(change in the gene pool) affect each population?
 How did the impact of genetic drift contrast
between the small population and the larger
population?
Gene Flow
 The exchange of genes with another population
 Occurs when fertile individuals or their gametes
migrate between populations
 Tends to reduce genetic differences between
populations
What have you learned?
 What is a gene pool?
 All of the alleles in all of the organisms that make up a
population
 What are the two main forces of evolutionary change
in gene pools other than natural selection?
 Genetic drift and gene flow
 How can genetic drift cause a substantial change in
allele frequencies in small populations?
 It can reduce genetic variations