EVOLUTION
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Evolution
• In the broadest sense, it simply means
“CHANGE”
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Evolution
• Change in what?
 More specifically, biological evolution is a
“change in the genetic composition of a
population of organisms from one
generation to the next”.
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Evolution
• “Nothing in biology makes sense,
except in the light of evolution”
………Theodosius Dobzhansky
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• Some things in biology seem a bit bizarre
until examined in the light of evolution, ---then it makes sense.
• Let’s examine a few instances and later
we’ll see how the activity might be
explained……….
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A pride of lions
Lion with dead cub
This
male lion
has just
killed a
lion cub
Why?
Ant/Fungus
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Peacocks and Peahens
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QUESTIONS ABOUT LIFE
Where to living things come from?
Why are there so many different kinds of
organisms on earth? Why do so many of
them resemble others?
How have these organisms become so good
at finding food, mates, fighting disease
and predators, producing offspring?
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Special Creation
• Has also been called:
• “Creation Science” or
“Intelligent Design Theory”
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SPECIAL CREATION
(“Intelligent Design Theory”)
1. All species (as well as this earth they
inhabit) were created recently (about
6000 yrs ago).
2. Species were created independently of
one another.
3. Species do not change through time.
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What about the age of the earth?
Catastrophism Past geological
upheaveals, like
Noah’s Flood, are
sufficient to
explain existing
geological
features. The
earth is roughly
6000 years old.
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Geological evidence
Gradualists – like James Hutton and
Sir Charles Lyell (founder of Geology,
pictured at the left) argued instead that
….slow, cumulative action of everyday
processes like sedimentation and erosion
were sufficient to explain geological
features. These processes came to be
known as uniformitarianism.
1797 - 1875
Their Conclusion:
The earth was not created
recently, it is very, very, very old!
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How old is the earth and has it
really changed ?
Hutton and his followers put together the
geologic time table using relative dating.
The actual dates were later determined
using radiometric dating. The earth is
approximately 4.5 billion years old!!
We now believe the earth has been
changing ever since it was formed
through processes such as continental
drift.
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If the earth itself has changed, have
living organisms changed?
Evidence:
 Direct observation:
There have been many
studies, such as those
by Peter and Rosemary
Grant who’ve studied
Darwin’s finches now
for more than 30 years,
and have witnessed
further evolution here.
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If the earth itself has changed, have
living organisms changed?
Evidence:
 Direct observation
 Vestigial structures:
- human appendix, or
tailbone (coccyx)
- lungs and pelvis in
whales
- eye sockets in blind
fish (Mexican tetra)
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If the earth itself has changed, have
living organisms changed?
Evidence:
 Direct Observation
 Vestigial Structures
 Fossil Record:
- extinction
It is estimated that 99% of all species that have ever
existed on this earth are now extinct.
The most probable likely happenstance for the
human race is extinction.
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If the earth itself has changed, have
living organisms changed?
Evidence:
 Direct Observation
 Vestigial Structures
 Fossil Record
- extinction
- succession some of these are
transitional forms
(e.g., Archaeopteryx
a reptile with wings)
If the earth itself has changed, have
living organisms changed?
Evidence:
 Direct Observation
 Vestigial Structures
 Fossil Record
- extinction
- succession
 Homologies:
-structural -
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If the earth itself has changed, have
living organisms changed?
Evidence:
 Direct Observation
 Vestigial Structures
 Fossil Record
- extinction
- succession
 Homologies
- structural
- molecular[see next slide]
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• Living things have, and
continue to, change!
• This is EVOLUTION.
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--Materialism-• A doctrine that states that observations are
to be explained in relation to the action of
observable processes….NOT spiritual
forces.
- Galileo Galilei was one of the first to
employ this doctrine.
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What about Darwin?
Darwin published “On The
Origin of Species by Means
of Natural Selection” in 1859.
 …… outlining the fact that
evolution was occurring.
 ….. proposing “Natural
Selection” as the
mechanism of evolution.
Charles R. Darwin
circa 1832
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“Evolution by Natural Selection”
• This is Darwin’s theory!
• Evolution has occurred by “descent
with modification”. All living
organisms have descended from a
common ancestor.
• Darwins’s theory has 4 postulates:
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Evolution by Natural Selection
1. Individuals within
populations vary.
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Evolution by Natural Selection
2. The variation
among individuals
is, at least in part,
…..inherited
(passed
on from parent to
offspring).
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Evolution by Natural Selection
3. In every generation, some individuals are
more successful at surviving and
reproducing than others.
Reproductive Potential
____________________________________________
Elephant
19 million in 750 years
Starfish
1079 in 16 years
Housefly
191x1018 in 5 months
Staph. aureus
cells would cover the
earth 7 ft deep in 48 hours
Evolution by Natural Selection
4. Survival and reproduction are NOT
random; individuals with variations that
are better at surviving and reproducing
are selected.
These individuals, in
turn, pass those inherited variations on
to their offspring and so on.
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Darwin Claimed Fitness was
• The ability of an individual to survive and
reproduce in its environment.
• Darwin emphasized ‘differential
reproduction’.
• He did not use the phrase, “survival of the
fittest”, which should probably be restated
as, “survival of the fit enough”.
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What is fit enough?
• Old Serengeti proverb………..
Every morning in Africa a gazelle wakes up. It
knows it must run faster than the fastest lion or it
will be killed. Every morning a lion wakes up. It
knows that it must outrun the slowest gazelle or
it will starve to death. It doesn’t matter whether
you are a lion or a gazelle, when the Sun comes
up, you’d better be running.
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What is differential reproduction?
Bird
Mates
twice
Has
Six
eggs
One
Lives
Bird
Mates
4 times
Has
Four
Eggs
None
Live
Bird
Mates
Once
Has
Two
Eggs
Two
Live
Differential Reproduction
Grow
to
adult
Mate and
Produce
6 eggs
All
Survive
to adult
Grow
to
adults
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How does differential
reproduction result in evolution?
• It causes changes in the genetic
composition of a population from one
generation to the next.
• How does it do that?
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Suppose we have a small
population (40) or rabbits in a field
and one (1) fox.
Let’s assume these rabbits have different colored coats as
shown below:
Color:
Number:
Gene type:
Black
12
(BB)
Brown
24
(Bb)
White
4
(bb)
How many “B” genes are there? 12x2+24 = 48 (60%)
How many “b” genes are there?
4x2+24 = 32 (40%)
The fox kills all white rabbits and
25% of the brown and black rabbits
• Remaining are:
Color:
Number:
Gene Type:
Black
9
BB
Brown
18
Bb
White
0
bb
How many “B” genes are left? 9x2+18 = 36 (66%)
How many “b” genes are left? 0x2+18 = 18 (33%)
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Gene Frequencies Change
• The frequency of the “B” gene changed
from 60% to 66%.
• The frequency of the “b” gene changed
from 40% to 33%.
• Here we see a “change in the genetic
composition of a population (of rabbits)
from one generation to the next”.
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The Process of Natural Selection is
NOT goal directed.
• The process of Natural Selection merely
ensures that individuals become better
adapted to their environment.
• Those that are better adapted live longer,
producing more offspring than others. These
offspring, because they are carrying the genes
that improved their parents fitness, also live
longer and have more offspring.
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What is the goal of individuals?
• While Natural Selection isn’t goal-directed,
all living organisms behave as if they have
an individual goal……
• TO GET AS MANY OF THEIR GENES AS
POSSIBLE INTO INDIVIDUALS IN THE
NEXT GENERATION…
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How to win the evolutionary race?
• Have as many offspring as
possible that have offspring!
• in other words…..
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“The one with the most grandkids
WINS!!”
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