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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 IslandsWhat 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
.
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.
.
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.
Natural Selection
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 ----------------
Continental Drift – Motion of continents about Earth's surface on plates of crust floating on the hot mantle.
Geographic Isolation
Continued…
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 RECORDFossil – 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 RECORDThe 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~ The theory that evolution
occurs slowly but steadily.
• Punctuated Equilibria~ The theory that species evolve 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