Theory of Evolution

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WHAT IS EVOLUTION?
Evolution is the gradual change in a species over
time.
A species is a group of similar organisms that can
mate with each other and produce fertile offspring.
Theory of Evolution: What is
the difference between a theory,
hypothesis, and a law?
CHARLES DARWIN – 1809-1882
• English naturalist
• Developed the theory of evolution by
natural selection
• Observed many species and fossils
• Traveled around the world on the ship
Beagle – Famous in the Galapagos Islands
• Why did some species survive while
others became extinct?
Charles Darwin – Galapagos Islands
What did Darwin observe on
the Galapagos Islands that led
him to propose his theory of
evolution?
EVIDENCE OF EVOLUTION
• Adaptations: A trait that helps an organism
survive and reproduce.
– Mimicry
– Camouflage
– Beak shape/size
.
Adaptations…Camouflage
what do you see?
WHAT IS NATURAL SELECTION?
Natural Selection is the process by which
individuals that are better adapted to their
environment are more likely to survive and
reproduce that other members of the same species.
Factors that affect the process of natural selection:
~ Overproduction
~ Competition
~ Variations: Any difference between individuals
of the same species.
.
Natural Selection
 Over a long period of time, natural
selection can lead to evolution. Helpful
variations gradually accumulate in a
species, while unfavorable ones
disappear.
Explain why variations are needed for
natural selection to occur.
How Do New Species Form?
• A new species can form when a group of
individuals remains separated from the rest
of its species long enough to evolve
different traits.
• Speciation
- Geographic Isolation
- Reproductive Isolation ----------------
Geographic
Isolation
Continued…
Continental Drift –
Motion of continents about
Earth's surface on plates of
crust floating on the hot
mantle.
OTHER EVIDENCE OF EVOLUTION
• FOSSILS
• EARLY DEVELOPMENT
(Embryos)
• ANATOMY (Body Structure)
– HOMOLOGOUS STRUCTURES
• SIMILARITIES IN DNA
Homologous
Structures –
similar
structures
that related
species have
inherited
from a
common
ancestor.
FOSSIL RECORD
Fossil – The preserved remains or traces of
an organism that lived in the past.
How Do Fossils Form?
Most fossils form when organisms that die
become buried in sediments (particles of
soil and rock). Others can be preserved in
ice, tar pits, or sap.
FOSSIL RECORD
The fossil record refers to the millions of fossils
scientists have collected.
What Do Fossils Reveal about extinct species?
~ How it looked
~ How it behaved
~ How it evolved (related species)
Group of jellyfish fossils has been uncovered
in Wisconsin, US
How Fast Does Evolution Occur?
• Gradualism
•
Punctuated Equilibria
~ The theory that evolution ~ The theory that species evolve
occurs slowly but steadily. during short periods of rapid change
Combining The Evidence
• Branching Tree – A diagram that shows
how scientists think different groups
organisms are related.
Geologic
Time Scale
Earth’s history is
organized into 4 eras:
• Precambrian
• Paleozoic
• Mesozoic
• Cenozoic
Some Questions to Ponder…
• Human evolution so far…
• 10,000 years from now…
– Where will humans live?
– How will our environment
change?
– What will the world look like?
– How Will The Forces of
Evolution Work On Our
Species?
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