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Transcript
Chapter 15 –
The Theory of Evolution
What is EVOLUTION?
A textbook definition of evolution…
“…evolution can be precisely defined as
any change in the frequency of alleles
within a gene pool from one generation
to the next."
- Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth Publishers, p.974
What is EVOLUTION?
Put a simpler way…

The change in a species over time.
I. What evidence is there for
Evolution?
A. Fossil records
B. Transitional species
C. Geological time and dating
D. Anatomical trends
E. Embryology
F. Biochemical/Molecular data
A. Fossil Record

What is a Fossil?
Preserved remains, imprints, or traces of an
organism that has survived.
i) Types of fossils


Mold: sediment hardens
around an organism
preserving the outside
shape.
Cast: sediments enter a
mold and harden.
Fossils (cont.)


Petrifaction: atoms in
living tissues are
replaced by minerals.
Imprint: footprints,
tracks, or tunnels made
by an organism.
B. Transitional Fossils

Fossils that show a relationship or
evolutionary link between two different
species of a family of organisms.
Archaeopteryx
Archaeopteryx
1) Reptile features:

Trunk region vertebrae are free.
In birds the trunk vertebrae are always fused together.

Neck attaches to skull from the rear.
As in dinosaurs not from below as in birds.
Archaeopteryx
2) Bird features:

Feathers.

Opposable hallux (big toe).

Pubis (hip bones) are elongated and
directed backward.
Protospinax
Protospinax
1) Ray features:

Flattened body.

Primitive teeth.

Spent large amounts of time on the sea
and ocean floors.
Protospinax
2) Shark Features:

5 foot long body.

Had a detached upper jaw.
Other transitional fossils
1)
2)
3)
4)
5)
6)
7)
Acanthostega
Canobius
Ichthyostega
Karaurus
Panaderichthys
Trematops
Vieraella
And Many More…
C. Geologic time dating

The Earth is 4.5 Billion Years Old!
If the Earth’s history was just one year long then…

Each day would be about 12 million years!

First bacteria = about the middle of March.

Dinosaurs don’t show up until late November.

Humans haven’t even been around a ½ day.
How do we know the earth is
that old?
By using the technique of radioactive
dating of different isotopes!
(Example: Carbon dating)
Other radioactive isotopes
Isotopes
Dating
Key Fission
Sample
Product
LutetiumHafnium-176
176
UraniumLead-206
238
UraniumLead-207
235
RubidiumStrontium-87
87
PotassiumArgon-40
40
Carbon-14
Nitrogen-14
Half-life
(years)
Effective Dating
Range
(years)
37 billion
early Earth
4.51
10 million to origin of
billion
Earth
0.704
10 million to origin of
billion
Earth
48.8
10 million to origin of
billion
Earth
1.25
100,000 to origin of
billion
Earth
5730 ± 40
0-100,000
D. Anatomical Trends
1. Homologous structures: structures with
the same general form and originating from
the same region of the embryo.
2. Vestigial structures: a structure that has
been greatly reduced with no apparent
function. (thought to at one time have a
purpose)
1. Homologous structures
2. Vestigial structures
Examples:
a. Whales have a
pelvis yet no feet.
b. Cave salamanders
have eyes although
they are blind.
c. Humans have a
tailbone but no tail.
E. Embryological development


Embryos of certain
species develop almost
identically especially in
early stages.
The embryos of all
vertebrates (animals
with backbones) have
gill slits and a tails,
which indicates that all
vertebrates may have
common ancestry.
F. Biochemical/Molecular
1) DNA and RNA are made of the
same nucleotides in ALL
organisms.
2) ATP is the energy molecule of
all life systems.
Biochemical/Molecular
3) The metabolism of different organisms is
based on the same complex biochemical
compounds.
4) Certain blood proteins are found in almost
every organisms.
5) The protein (cytochrome c) is essential for all
organisms that perform aerobic respiration.
II. Developing the
“Theory of Evolution”

The Theory of Evolution
is a carefully reasoned and
tested hypothesis about how
evolutionary change occurs.
Theories of Evolution
A. Jean Baptiste de Lamarck (1809)
His theory was eventually disproved but it
was the first attempt to support evolution.
B. Charles Darwin & Alfred Wallace (1858)
Came up with an almost identical theory on
evolution although each worked separately.
(Basis for our current theory of evolution.)
A. Theory of Acquired Characteristics
(Lamarck)
Also known as “Theory of Use and Disuse”
 Organisms acquired traits during their lifetime
and then passed those traits to their
offspring.
Example:
If giraffes stretched their necks to reach leaves
higher on the trees, then their offspring would
have longer necks.
Lamarck vs. Darwin
Darwin said:
 Giraffes with long necks
survived and those with
short necks died because
they had to compete for
food that was higher up
in trees.
Consequently, they then
passed on the stretched
 Consequently, the long
(acquired) long-necks
neck genes were passed
to their offspring.
on and over time the
average giraffe had a
longer neck.
Lamarck said:
 Giraffes STRETCHED
their short necks to
reach food.

B. Charles Darwin


Charles Darwin was born
on February 12, 1809 in
Shrewsbury, England.
Contrary to popular belief,
Darwin was not the first
person to describe the
concept of evolution, but
he was the one who gave it
its popularity.
Charles Darwin



Darwin set sail on the H.M.S. Beagle (1831-1836)
to survey the south seas (mainly South America
and the Galapagos Islands) to collect plants and
animals.
On the Galapagos Islands, Darwin observed
species that lived no where else in the world.
These observations led Darwin to write a book in
1859 called “The Origin of the Species by Means
of Natural Selection”.
Galapagos Islands
Galapagos Islands:
Darwin’s Finches
Darwin’s Finches
1. All of the finches came from the same 2
parent finches.
2. The birds reproduced and some of their
offspring flew to different islands.
3. Each population adapted to their unique
environment.
4. Finches prefer not to fly long distances.
Thus, reproductive isolation occurred.
5. Birds that lived on the same island evolved
in their own unique ways leading to
formation of new species of finch.
Darwin’s Finches
There are 13 different species of
finches on the Galapagos Islands all
evolved from a single ancestor.
Each species of finch live on a different
island and they have adapted to that
particular environment.
Consequently, each species has developed
their own set of behavioral and physical
differences.
Example:
The Galapagos finches
can vary greatly. Some
eat small seeds while
others prefer large seeds,
and some eat ticks all
because of differences in
their beaks.
III. Natural Selection
Darwin knew nothing of genes,
but what he did have were
many observations and a little
foresight that provided the
driving force for evolution.
Darwin’s Field Observations
1. Organisms produce more offspring than can
survive which creates competition.
Darwin’s Field Observations
2. Not all members of a species are exactly alike.
Darwin’s Field Observations
3. The members with the most favorable
traits to their environment will survive
(survivial of the fittest).
4. Survivors with the favorable traits will
pass them on to their offspring.
Darwin’s Field Observations
5. In time, the most favorable traits may
become adaptations for the survival of
that species.
6. If the new species is different enough
from its ancestors we say a new species
is created
Modern Theory of Evolution

Same as what Charles Darwin and
Alfred Wallace described, AND adding
the new information that:
“Mutations are a way of producing
changes in members of a species.”
Modern Theory of Evolution
“Population isolation leads to the formation of new
species because they become so different from
one another that they cannot interbreed.”
Modern Theory of Evolution
“Mass and minor extinctions lead to the
replacement of that species by other species
that are better suited to the environment.”
General rules about Evolution
“When facing a constantly changing
environment a species must get M.A.D.”
(Migrate, Adapt, or Die)
IV. Types of Evolution

Evolution is not unidirectional. Some
species grow less alike, some grow
more alike, and some change in
response to changes in others. These
are the “Patterns in Evolution”.
A. Divergent Evolution

The process where two or more related
species become more and more dissimilar.
Example:
1. The color of the Red Fox helps it blend in
with the trees in its environment while sandy
color of the Kit Fox helps it blend into the
desert.
B. Convergent Evolution

Species from different evolutionary branches
may come to resemble one another if they
live in very similar environments.
Example:
1. The Ostrich (Africa) and Emu (Australia) look
alike due to the similar environments in which
they live.
C. Coevolution

Evolutionary change, in which one species act
as a selective force on a second species,
inducing adaptations that in turn act as a
selective force on the first species.
Example:
1. Humming Birds have a beak relative to the
length of the plants with flowers that have
longer or shorter tubes.
Any Questions?


“It is the mark of an educated mind to
be able to entertain a thought without
accepting it.”
–
Aristotle
“It is not the strongest of the species
that survives, nor the most intelligent,
but the most responsive to change.” –
Darwin