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Evolution
Change over time
What is evolution?
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Evolution is change over time
The theory of evolution states that evolution
is the process by which modern organisms
have descended from previous organisms
What is a theory?



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A common misconception is that a theory is
simply a statement of ones ideas.
In a scientific sense this is not true
A theory is a well supported testable
explanation of phenomena that have occurred
in the natural world
Some common theories include
 Gravity, the big bang and evolution
Who was this Darwin guy?


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Charles came from a family of
doctors
He dropped out of med school
Eventually he signed on to the
HMS
Beagle as the ships biologist

Charles
Darwin,
1859
Most educated people in Europe
and the Americas during the 19th
century had their first full
exposure to the concept of
evolution through the writings of
Charles Darwin . Clearly, he did
not invent the idea. That
happened long before he was
born. However, he carried out
the necessary research to
conclusively document that
evolution has occurred and then
made the idea acceptable for
scientists and the general
public. This was not easy since
the idea of evolution had been
strongly associated with radical
scientific and political views
coming out of post-revolutionary
France. These ideas were widely
considered to be a threat to the
established social and political

Charles Darwin, 1859
http://anthro.palomar.edu/evolve/evolve_2.ht
What does this have to do
with anything?

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Darwin’s ship sailed to the Galapagos islands
where Darwin made many observations and
collections
While the ship was at sea, and between bouts
of sea sickness, Darwin studied these
specimens.

The voyage of the Beagle
Great
Britain
Europe
North
America
Pacific
Ocean
Atlantic
Ocean
Africa
Galápagos
Islands
Equator
South
America
Australia
Cape of
Good Hope
Tasmania
Cape Horn
Tierra del Fuego
http://www.rit.edu/~rhrsbi/GalapagosPages/D
arwinFinch.html
New
Zealand
Figure 13.1B
Darwin’s Observations


Darwin was intrigued by how well adapted plants
and animals were to their environment
Darwin also collected fossils during his voyage
 He noticed that some fossils very closely
resembled modern organisms and some did not
 Why?
organisms produce more offspring than
the environment can support
 organisms vary in many characteristics
 these variations can be inherited

Differences Among
Organisms

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The differences that Darwin observed within
organisms was identified as adaptations
Adaptations- characteristics that helps and
organism survive and reproduce in its
environment
Ex-color of moths, hummingbirds long beak
or the red color of poisonous berries.

The Galápagos Islands have species found in no
other part of the world, though similar ones
exist on the west coast of South
America. Darwin was struck by the fact that
the birds were slightly different from one
island to another. He realized that the key to
why this difference existed was connected
with the fact that the various species live in
different kinds of environments.
http://anthro.palomar.edu/evolve/evolve_2.htm

Darwin identified 13 species
of finches in the Galápagos
Islands. This was puzzling
since he knew of only one
species of this bird on the
mainland of South America,
nearly 600 miles to the east,
where they had all presumably
originated. He observed that
the Galápagos species
differed from each other in
beak size and shape. He also
noted that the beak varieties
were associated with diets
based on different foods. He
concluded that when the
original South American
finches reached the islands,
they dispersed to different
environments where they had
to adapt to different
conditions. Over many
generations, they changed
anatomically in ways that
allowed them to get enough
food and survive to reproduce.
The Origin of Species


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This was the title of
Darwin’s book in which
he outlined the theory
of…
Evolution by Natural
Selection
Darwin based much of
this theory on work that
had been done by
English farmers
What is a species?


A group of similar organisms that can breed
and produce fertile offspring
Examples
 People
 Dogs

Not all animals that breed are the same species
A horse and a
donkey may
produce a hybrid
offspring, a mule
 Mules are sterile

Figure 14.2C
Prove it to me

The fossil record
 Fossils are the remains of once living
organisms
 Aquatic fossils
(shells, fish, etc.) are found in areas that
are now deserts
 Many different species were present on
this planet in the past
 This shows the earth is constantly changing
So how old is this place?
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The oldest rocks on this planet are around 3.5
billion years old
The oldest rocks on the moon are around 4.5
billion years old
The oldest meteorites found on the planet
are around 4.5 billion years old
These ages are determined by gauging the
decay of uranium which has a 1/2 life around
4.5 billion years
B) Comparing Organisms-
1) Homologous Structuresstructures that have a common origin
but not necessarily a common function.
Ex. Arm, wing vs. fin.
-This common
bone
combination was
passed from
one species to
the next.
2) Vestigial structures- structures in
the body that have no current function
for the organism. (But in the past it
did)
Ex. Appendix in humans,
pelvis in whales.
-Left over structure not needed today to be
3) Embryo
similarities- human
embryos and
embryos of other
very different
animals are very
similar early on in
development.
Evidence of Evolution

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Vestigial organs
 Organs that serve no purpose
Homologous structures
Biochemical evidence
 The similarity of DNA structure and genes
found in all life
Experiments
 In a laboratory setting it is possible to
cause a population of organisms to evolve
Vestigial Organs

Organs that are no longer useful to the organism
 Your appendix
 Eyes on the naked mole rat
 These organs were present and used in the past
and have since become useless
 Natural selection has favored the eyeless moles
4. Biochemical Evidence
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By comparing the DNA and RNA of organisms
scientists can quantify how alike or different
two organisms are
There is a high level of similarity among all
organisms
All life on this planet is over 90% the same
when viewed at the DNA level
Evolution in the lab
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It is possible to make a population of
organisms evolve in a particular manner
Take for example a population of insects
 If the population is sprayed with a certain
pesticide and some survive, the surviving
insect will go on to reproduce
 Over time if this resistance to pesticide is
selected for then the gene will become part
of the population
Artificial Selection
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Farmers breed plants and livestock to gain
desired characteristics.
In artificial selection, nature provided the
variation among the different organisms, and
humans selected those variations that they
found useful.
A good example of this is the different
breeds of dogs
Natural Selection
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Over reproduction of offspring
There’s a struggle for existence
There is competeion for food, living space, & mates
There is variation within the population
Those members that are best suited
(“fittest”) will survive, reproduce and pass
their traits on to the next generation.
Natural Selection cont.

Survival of the Fittest
 What does it mean to be fit?
 Darwin described this as an animals ability to
survive and reproduce in its environment.
 Fitness is the result of adaptations
 An adaptation is any inherited trait that
increases an organisms chance of survival
 These adaptations can be physical or
behavioral
How do species form?
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Separation
Reproductive barriers
Genetic mutation
Adaptive radiation
Separation
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When two populations become separated by a
geologic barrier
The populations on either side can change
independently
When the two populations are brought back
together they may now be different species
Ground squirrels and the
Grand Canyon
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Two different species of ground squirrels can be
found on either side of the grand canyon
The two species look similar but cannot interbreed
Gene Flow (Thick Arrow – High)
(Thin Arrow – Low)
Gene Flow (Thick Arrow – High)
(Thin Arrow – Low)
Gene Flow (Thick Arrow – High)
(Thin Arrow – Low)
Gene Flow (Thick Arrow – High)
(Thin Arrow – Low)
Gene Flow (Thick Arrow – High)
(Thin Arrow – Low)
Would gene flow, across this
Canyon, in hawks be influenced
in the same manner as it is
in squirrels?
No. WHY?
Reproductive Barriers
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Physical incompatibility
 EX. Dogs- Are a Chihuahua and a Great
Dane the same species?
Different mating habits
 Ex. Different mating grounds, times, rituals
Mutation
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Common in plants
Can result in new genes or polyploidy
organisms
Polyploidy can result from a mistake in cell
reproduction
Mitosis Error
Prophase Cell
Mitosis Error
Prophase Cell
Metaphase
Mitosis Error
Prophase
Metaphase
Anaphase
Normal
Mitosis Error
Prophase
Metaphase
Anaphase
Mitosis
Error
Mitosis Error
Prophase
Metaphase
Anaphase
Mitosis
Error
2n= 8
chromosomes
2n= 8
chromosomes
Original cell:
2n = 4
Adaptive Radiation
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The emergence of many new species when a
common ancestor is introduced into new and
diverse environments
Example- Darwin's Finches
Island
Forms
Mainland
ancestor
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Adaptive radiation on an island chain
1
A
Species A
from mainland
2
B
Species A
Evolves into
Species B
B
B
3
B
C
4
C
C
C
C D
D
D
5
Figure 14.4B
How predation can lead to
evolution
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Coevoloution- A series of reciprocal
adaptations in two species
 A change in one species results in selection
in another
 Example Cheetah and Gazelle
 Both can run over 60 mph
Convergent Evolution
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When two organisms develop similar traits
due to similar environments but are not
closely related
Bats and Birds
 Both have developed wings for flight