Transcript ch16.3 & 16.4 Darwin`s Case & Evidence

Darwin’s Theory of Evolution
Chapter 16-3
Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006
A.Darwin Presents His Case
• In 1859,
On the Origin of Species
presented evidence
and proposed a
mechanism for evolution
that he called
NATURAL SELECTION
http://www.loc.gov/exhibits/world/images/s125.jpg
B. HIS CONCLUSIONS
1. GENETIC VARIATION (differences)
is found naturally in all populations
http://www3.nationalgeographic.com/animals/images/primary/zebra-herd.jpg
2. Any inherited characteristic
that increases an organism’s
chance of survival =
ADAPTATION
http://www.wildlife-traps.com/skunks.html
http://www.atomtigerzoo.com/photos/images/20060421233733_duckfeet.jpg
http://www.3kitty.org/travelrama/Photos/123-21-4x6.jpg
GALAPAGOS FINCHES
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The _____
beaks of Galapagos finches have
adapted
______ to eating a variety
_____ of foods
_____.
3. STRUGGLE FOR EXISTENCE
means members of each species
must compete for food, space, and
other resources.
http://www.wasatchcomputers.net/gallery/elk_fight.jpg
4. SURVIVAL OF THE FITTEST
organisms which are better adapted
to the environment will survive and
reproduce, passing on their genes.
http://www.poster.net/bedard/bed202.jpg
http://www.cartoonstock.com/newscartoons/cartoonists/cga/lowres/cgan170l.jpg
5. Ability of an individual to
survive and reproduce in its
specific environment
fitness
= ___________
C. DARWIN’S THEORY
Over time, NATURAL SELECTION
results in variation in inherited
characteristics of a population.
These changes increase a
species’ fitness in its
environment.
How Does Evolution Really Work?
DESCENT WITH MODIFICATION
- suggests that each species has
descended, with changes,
from other species over time.
- this idea suggests that all living
species are related to each other
and share a common ancestor.
D. Evidence of Evolution
HOMOLOGOUS Structures
1._____________________
Similar features that originated in a shared
common ancestor
Image from:
http://www.angelfire.com/ab7/evolution12/evolutionclues.html
Ex: limbs of vertebrates, look very
different, but are made from the
same bones because
they are made from
the same
clump of
embryonic
cells.
EMBRYOS OF
DIFFERENT

VERTEBRATES
Image from:
http://www.angelfire.com/ab7/evolution12/evolutionclues.html
2. VESTIGIAL Structures
Some homologous structures
are vestigial & have no useful function
even though they are still present.
Ex: like hipbones in whales
http://www.txtwriter.com/backgrounders/Evolution/EVpage12.html
Ex: In humans, the cecum
is shrunken and unused. In ancestors
used to digest plants.
It is our appendix.
http://www.medicalgeo.com/images/appendix.gif
3. ANALAGOUS Structures
serve identical functions
and look somewhat
alike
ex: wings of bird &
insect
Differ greatly in anatomy
Can infer wings evolved
independently & share
a very remote
ancestor
http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif
PBS EVOLUTION VIDEO CLIPS
Isn’t Evolution Just a Theory?
QuickTime
Who was Charles Darwin?
QuickTime
How Do we Know Evolution Happens?
QuickTime
How Does Evolution Really Work?
QuickTime |
Why Does Evolution Matter Now?
QuickTime
Why is Evolution Controversial Anyway?
QuickTime
4. Molecular Biology -Similarities
in DNA
sequences
provide
evidence of
common
descent
-Universal
genetic code
Image from: BIOLOGY AP EDITION by Campbell and Reece; Prentice Hall Publishing©2005
Human- 46 chromosomes
Chimpanzee- 48 chromosomes
-Similar karyotypes suggest an
evolutionary relationship.
• Homologous Proteins
– share structural & chemical (amino
acid) similarities between species