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Warm up
1. Modern technology could be used to clone animals (like you
favorite dog). Cloned animals would resemble the original pets
because:
2. How is the process of gene therapy used to treat cystic
fibrosis?
3. Describe the procedure represented in the diagram
below using these terms?




Restriction enzyme
Recombinant DNA
Plasmid
Vector
Who committed
the crime and
why?
Explain the
process
What is similar
about these two
processes?
Mechanisms of Evolution
How did all life on Earth come
from a few cells?
Speciation
Mechanisms of Evolution
 Individuals DO NOT
evolve, populations do.
 The population is the
smallest unit of evolution
because acquired traits
in an individual cannot
be passed on (inherited
by offspring).
Mechanisms of Evolution
 However, different
traits already
present in a
population can be
“selected”, changing
the population
Mechanisms of Evolution
 Evolution occurs
when the gene pool
(all of the genes of a
population)
changes.
 A change in
genotype may lead
to a change in
phenotype.
 Evolution acts on
the phenotype.
Mechanisms of Evolution
 Mutations are random
changes in DNA and
may lead to a new
phenotype.
 Mutations provide the
raw material for
evolution - diversity.
 For example, a
mutation causing white
fur in Arctic foxes may
lead to better
camouflage in winter.
Fill It In …
Mutations -->
______________ in __________ -->
change in ______________
Mechanisms of Evolution
 The environment also plays
a key role in evolution.
 Environmental changes are
natures “selection forces”
that act upon the phenotype
ranges caused by genes.
 There are three basic patters
by which natural selection
occurs:
Patterns of natural selection:
 Stabilizing
selection favors the
“average”
phenotype in a
population.
Patterns of natural selection:
 Directional
selection favors the
ONE of the extreme
ends of the “typical”
distribution
Patterns of natural selection:
 Disruptive
selection favors the
BOTH of the
extreme ends of the
“typical” distribution
Fill It In …
Three types of Natural Selection:
1.
2.
3.
Speciation
 Speciation is the
development of a
new species.
 A species is defined
as a group of
organisms that can
produce fertile
offspring.
Speciation
 Species- a group of individuals that
breed and produce fertile offspring
 What a about a Liger? A Mule?
Speciation
 Speciation occurs when a population is separated,
usually due to a geographical barrier, and natural
selection changes the population so much the two
groups could no longer interbreed.
 Therefore, geographic isolation leads to
reproductive isolation.
What is Speciation
 Speciation: is a lineage- splitting even
that produces one or more new species
 formation of new species
Speciation
Causes of Speciation
 As new species evolve, populations become
reproductively isolated from each other
 Reproductive isolation- occurrence in which the
members of two populations cannot interbreed and
produce fertile offspring
 Populations have
separate gene pools
Causes of Speciation
 Behavioral Isolation- occurs when two
populations are capable of interbreeding but
have differences in courtship rituals or other
reproductive strategies that involve behavior
 Bird songs
 Temporal Isolation- two or more species
reproduce at different times
 Orchid pollen release
Fill It In …
Geographic isolation is related to
speciation because …
Genetic Drift
 By Chance- Certain
individuals might leave
more offspring (alleles
that others)
 Over Time- an allele
can become more
and more common
 founder effect- a
situation in which
allele frequencies
change as a result of
the migration of a
small subgroup of a
population
Rate of Evolution
 Timeframes of
evolution differ
based on the
environment and the
population.
 The fossil record
provides evidence
for two rates of
speciation:
Rate of Evolution
 Gradualism
describes speciation
that occurs over a
long period of time
due to the
accumulation of
small changes.
Rate of Evolution
 Punctuated
equilibrium
describes speciation
that occurs in rapid
bursts that may be
separated by 1000’s
of years of stability.
 The primary
stimulus is
environmental
change
Rate of Evolution
Fill It In …
Venn Diagram: (Gradualism vs.
Punctuated Equilibrium)

Causes
of
Speciation
Selective Pressure:
 Directional Selection
 Stabilizing Selection
 Disruptive Selection
Adaptive Radiation
 Individuals will diversify rapidly to fit a
NICHE in the environment
 Usually due to change in the environment
 New Resources= new niches to fill
Characterized by
caring for young in
pouches.
Evolved/ Branched
from common
ancestor about 160
million years ago
Check Yourself!
1.
2.
3.
4.
5.
6.
Why can’t individuals evolve?
What provides the raw material for evolution?
What are the three types of natural selection?
What is speciation?
What conditions lead to reproductive isolation?
Name the two time frames for speciation.
Check Yourself!
1. Why can’t individuals evolve?
AQUIRED TRAITS IN AN INDIVIDUAL
CANNOT BE PASSED ON TO OFFSPRING
Check Yourself!
2. What provides the raw material for evolution?
MUTATIONS
Check Yourself!
3. What are the three types of natural selection?
STABILIZING SELECTION
DIRECTIONAL SELECTION
DISRUPTIVE SELECTION
Check Yourself!
4. What is speciation?
THE DEVELOPMENT OF A NEW SPECIES
Check Yourself!
5. What conditions lead to reproductive isolation?
GEOGRAPHIC ISOLATION
Check Yourself!
6. Name the two time frames for speciation.
GRADUALISM
PUNCTUATED EQUILIBRIUM