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Theory of Evolution
Chapter 15
Theory
 Science
= Hypotheses that
pass testing. Highest honor in
science.
 Common
Usage = An idea, not
necessarily supported with
facts or tests.
How did living things
achieve so much variety?
Answer:
Changes in DNA
(mutations!)
Gradualism vs.
Punctuated Equilibrium


Gradualism- small mutations that occur
frequently.
Punctuated Equilibrium- many mutations that
occur all at once
Jean Baptiste Lemarck

Use and disuse.

A giraffe’s neck is long after many generations of
giraffe’s stretching their necks.

Can you see what is wrong with this????
Endler
•
Experimented with Guppies.
•
Without predators…
•
•
increase in male guppies with large and
brightly colored tails, because they are
favored by females.
With predators…
•
decrease in male guppies with large and
brightly colored tails, because the
flashier fish are eaten by predators.
Charles Darwin

Rode in HMS Beagle along coastal
South America.

Noticed variety in tropical life.

Survival of the fittest.

All life is linked from a common
ancestor.
Did you know…
Darwin never used the word
‘evolution.’
Darwin’s Voyage
Galapagos Islands
Galapagos Islands--A laboratory for evolutionary biology
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Darwin’s Theory of
Natural Selection



There is variation within a population.
Some variations are good (helpful).
Not all young produced in a generation
can survive!



This leads to a struggle for existence.
Survival of the fittest.
Those that survive and reproduce are those
with the best variations for that specific
environment.
Species

Group of similar organisms.

Can interbreed successfully in nature.
 Offspring are healthy
 Offspring are fertile (can reproduce)
These organisms are not
new species…Why?

Mule

Liger
Answer…
They are sterile! (Cannot produce children.)
Speciation
 Evolution
of several species from 1
ancestor species.
 Can
be from isolation.
 Geographic isolation
 Reproductive isolation
Geographic Isolation

Organisms are separated by a barrier.
 Islands that have broken apart.
 Earthquake produces a large crack.
Reproductive Isolation

Organisms that used to
breed don’t any longer.

Many Reasons…
 They now make
sterile offspring.
 They now mate in
different seasons.
Mutations are successful if
they help the organism
survive and produce
fertile offspring!
Evidence for Evolution




Fossils
DNA similarities
Homologous Structures
Similar embryo
development
Fossil Evidence



The age of fossils can be determined by radioactive
decay OR by dating rocks around them.
Fossils of simpler organisms are found in older rocks.
Fossils of more complex organisms are found in newer
rocks.
Fossil
Evidence
How fossils are “made”…
Fossil
Evidence
Dating Fossils
Fossil
Evidence
14Carbon
Dating
1. Amount is constant (100% 14C) while alive.
2. Organism dies.
3. 14C amount declines (due to radioactive
decay) when organism dies.
Fossil
Evidence
DNA Similarities

The more similar the DNA, the more
closely related organisms are.
 Your DNA is closer to your sister’s than
your cousin’s.
 Your DNA is closer to a pig than a duck.
DNA
Evidence
Similarities in DNA show how closely
related organisms are to each other.
DNA
Evidence
 Comparing
chromosomes
of humans
and
chimpanzee
DNA
Evidence
Chromosomes:
Human
Chimpanzee
Gorilla
Orangutan
DNA
Evidence
Hominoid Cladogram:


Lengths and positions of arrow lines reflect the:
 # of chromosome changes
 relative timing
 likely relationship
‘A’ refers to the Ancestral origin.
DNA
Evidence
Humans did NOT
evolve from apes!
We had a similar ancestor and BOTH of us
evolved from that ancestor.
 It’s no wonder that we have many of the
same DNA sequences!

DNA
Evidence
Homologous Structures
 Similar
bone structures.
Homologous Evidence
Similar Embryo Development


Embryos in all animals go
through similar stages.
Humans even produce
pharyngeal slits that are
not seen later.
Embryo Evidence
Other Stuff…
Analogous Structures
 Similar
function evolves separately!
2 Versions of the
Hominoid Family Tree
3 feet, 8 inches tall!
Lucy



Discovered in 1974.
3.2 million year old
bones.
Almost half of her
bones were found!
Ethiopia
(in Africa)
Evolution Observed:
Peppered Moths
Light moths
Dark moths
Less pollution
More pollution
Opposition to the Theory of Evolution
•
Evolutionary theory, more than any
other scientific theory, is regularly
challenged.
•
Much of the objection comes from a
mistaken view of what a scientific
theory represents.
– Some of the evidence for evolution is
historical in nature, and cannot be
demonstrated experimentally.
– Consistency in the evidence derived from
many sources, using many methods, from
within biology (e.g., embryology,
biochemistry) and from other disciplines
(geology, nuclear chemistry), for more than a
hundred years has convinced most scientists
that the core principles of evolution
accurately describe the story of life on Earth.
The End
Observation #5

Much of this variation is heritable.
Survival is not random, but depends in part on
the hereditary constitution of the surviving
individuals. Those individuals whose inherited
characteristics fit them best to their
environment are likely to leave more offspring
than less fit individuals.
 This unequal ability to survive and reproduce
will lead to a gradual change in a population
