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Unlocking the Mystery:
Evolution
Evolution provides a unifying theory
for the diversity of life and
similarities between the species.
Table of Contents
What is evolution?
• Definition
How does evolution occur?
• Mechanisms
• Evidence
• Patterns
–
–
–
–
Fossils
Anatomy
Embryology
Biochemical
• Phylogeny
What is evolution?
Descent with
Modification
From a
Common Ancestor
So, what exactly
is modified?
A CHANGE OVER TIME?
Is this evolution?
What must change?
A CHANGE IN INHERITED TRAITS
So Evolution is…
A change in genetics
NOT
physical
appearance!
For Example…
Is this evolution?
• Oh, no 2 generation drought
Is this evolution?
• Food source diminishing
• Several generations later…
• New generation beetles
weigh less
• Why?
• 90% green beetles
• 70% brown
• Why?
To Elaborate…
• 1st scenario
– Next generation not genetically different
– Weight depends on amount of food
• 2nd scenario
– Next generation genetically different
– Color depends on genetics
Which is the best definition of
evolution?
A. A change in a species over time
B. A change in physical appearance of a species
C. A change in an organism’s genetics
D. A change in a population’s genetics
Remember
Evolution is…
A change in genetics
How do we know
it happens?
So where’s the evidence
• Life has existed for billions of years
• Life has changed
• Where is all the evidence?
Evidence from:
• Fossils
• Embryology
• Anatomy
• Biochemical
Fossil Evidence
• Shows transitional forms
Anatomy:
Homologous Structures
Similar structures show common ancestry
View more examples or Fish out of Water
Anatomy:
Analogous Structures
Different ancestry but similar structure and function
View more examples
Anatomy: Vestigial structures
Remnants of ancestral structures that are no longer
used
Here are some more examples
We are
modified versions
of our
ancestors
We inherited their
characteristics
Which structure(s) is best represented
in the image?
A. Analogous
B. Embryonic
C. Homologous
D. Vestigial
Which structure(s) provides the
weakest evidence for common
ancestry?
A. Analogous
C. Homologous
B. Embryonic
D. Vestigial
The human appendix is best identified
as which of these structures?
A. Analogous
C. Homologous
B. Embryonic
D. Vestigial
Embryology
• Similarities in
development
• Same genes produce
different structures
Biochemical
• DNA links all life to a common ancestor
• Compare DNA (or protein) sequences to find
relatedness
– More similar = more related
– More differences = less related
Mapping Ancestry:
Phylogenies
How do we read this?
New Species
2 species from 1
Last common ancestor
Keeps Going and Going…
1.Evolution produces a pattern of relationships A B C D among lineages that is tree-like, not ladder-like.
Keep in mind…
• Evolution produces a pattern of relationships
A B C D among lineages that is tree-like, not
ladder-like.
Keep in mind…
• Just because we tend to read phylogenies
from left to right, there is no correlation with
level of “ advancement.”
Keep in mind…
Keep in mind…
• Humans experienced
same history
• Humans did not evolve
from chimpanzees
– We have a common
ancestor
– We are related to not
evolved from!!!
Birds are Dinosaurs
Phylogenies are visuals of the
relatedness of species
How does
it happen?
Could this work?
How about this?
Descent with Modification
• Inherit traits from parents
• Provides genetic variation in a population
• Some variations survive and reproduce
• Change in gene frequency within a population
over time!!
Giraffe Necks
• General increase in long neck gene over time!
One idea:
Inheritance of Acquired Characteristics
Inheritance of Acquired Characteristics
• Giraffe keeps stretching
neck
• It gets longer
• Passed on to new
generation
• What if we cut off a
mouse tail?
Comparing Ideas
Genetic
Variation
is a MUST!
Sources of variation
Mutation
– A change in DNA sequence
Sources of Variation
Gene Flow
– Genes move from one population to another
– Aka migration
Sources of Variation
1. Sexual reproduction
– Creates new gene combinations
– Genetic shuffling
Recap: Sources
• Mutation
– DNA is altered
• Gene Flow or migration
– Introduction of new source of genes
• Sexual Reproduction
– New combinations
Genetic Drift
• “Lucky” individuals survive and reproduce
• No selection- just random events
Natural Selection
• Genetic variation in population
• Variation is inherited
• More fit variations survive
• Reproduce
What is
?
Survival of the fittest
• Fit =
ability for genotype
to survive and reproduce
• Depends on environment!!!
Adaptations
• Common feature that provides improved
function
• Anatomical
• Behavioral
• Biochemical or physiological
– Better protein
Coevolution
• Two species affect each other’s evolution
• Why does this moth have such a long tongue?
Coevolution
• It gets its food from here!
Patterns of Evolution
How fast does it occur?
Gradualism
Gradualism
• Transitional forms in
fossil record
• Evidence of gradual
change
Punctuated Equilibrium
• Big changes, short time
• Few to no transitions
Punctuated Equilibrium
Little evolution occurring
Punctuated Equilibrium
Oh no, the water is gong down!!!
Reproductive isolation
Punctuated Equilibrium
Strong selection & rapid change
Punctuated Equilibrium
Long time, no see…
Punctuated Equilibrium
I win!
Punctuated Equilibrium
No record of change is preserved!
Does No Transitions Mean Fast
Evolution?
3 Explanations for same data!
Diversity
• Why do some lineages lead to millions when
others only lead to a few?
Opportunity Knocks
• Environment presents opportunities
• Lineage takes advantage
Adaptive Radiation
• One species gives rise to many?
• But how?
Adaptive Radiation
• Organisms exploit a new niche or resource
• Specialization
1.
Species A migrates from the
mainland to the first island.
2.
Isolated from the mainland,
species A evolves to species B.
Species B migrates to the
second island.
3.
4.
5.
6.
Species B evolves in species C.
Species C recolonizes the first
islands, but is now unable to
reproduce with species B.
Species C migrates to the third
island.
7.
8.
Species C evolves into species D.
Species D migrates to the first
and second island.
9.
Species D evolves to species E.
1.
Species A migrates from the
mainland to the first island.
2.
Isolated from the mainland,
species A evolves to species B.
Species B migrates to the
second island.
3.
4.
5.
6.
Species B evolves in species C.
Species C recolonizes the first
islands, but is now unable to
reproduce with species B.
Species C migrates to the third
island.
7.
8.
Species C evolves into species D.
Species D migrates to the first
and second island.
9.
Species D evolves to species E.
1.
Species A migrates from the
mainland to the first island.
2.
Isolated from the mainland,
species A evolves to species B.
Species B migrates to the
second island.
3.
4.
5.
6.
Species B evolves in species C.
Species C recolonizes the first
islands, but is now unable to
reproduce with species B.
Species C migrates to the third
island.
7.
8.
Species C evolves into species D.
Species D migrates to the first
and second island.
9.
Species D evolves to species E.
1.
Species A migrates from the
mainland to the first island.
2.
Isolated from the mainland,
species A evolves to species B.
Species B migrates to the
second island.
3.
4.
5.
6.
Species B evolves in species C.
Species C recolonizes the first
islands, but is now unable to
reproduce with species B.
Species C migrates to the third
island.
7.
8.
Species C evolves into species D.
Species D migrates to the first
and second island.
9.
Species D evolves to species E.
1.
Species A migrates from the
mainland to the first island.
2.
Isolated from the mainland,
species A evolves to species B.
Species B migrates to the
second island.
3.
4.
5.
6.
Species B evolves in species C.
Species C recolonizes the first
islands, but is now unable to
reproduce with species B.
Species C migrates to the third
island.
7.
8.
Species C evolves into species D.
Species D migrates to the first
and second island.
9.
Species D evolves to species E.
The Galapagos Islands
The Finches
Specialization
Types of Selection
Directional
• One extreme is
selected for
– SURVIVE AND
REPRODUCE
• Produces a change in
genetics
Stabilizing
• Average is selected for
– SURVIVE AND
REPRODUCE
• Produces a change in
genetics
Disruptive
• Both extremes
selected for
– SURVIVE AND
REPRODUCE
• Produces a change in
genetics
There is no end product!