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Evolution Unit . Pages 296 – 335 Tuesday, June 10, 2014 Monkemeier Part 1: The Idea of Evolution. Early in the 18 th century . . . Scientists believed that All species were permanent and unchanging! The Earth was only thousands – and not billions of years old!.
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Evolution Unit Pages 296 – 335 Tuesday, June 10, 2014 Monkemeier Part 1: The Idea of Evolution
Early in the 18th century . . . • Scientists believed that • All species were permanent and unchanging! • The Earth was only thousands – and not billions of years old!
Then . . . Scientists started to present evidence • Scientists started to present fossil evidence that species on Earth have changed over time!
Then Scientists began to present evidence • That the Earth is MUCH older than what they thought!
By the 1800’s • Scientists started studying rock layers known as strata. • Superposition Principle: lower stata were formed first and therefore are the oldest.
Fossils • By the 1800’s scientists found that different rock layers (strata) hold fossils of different kinds of organisms. • Georges Cuvier (1769 -1832) spent years studying and reconstructing the appearance of unique organisms from fossil bones.
Cuvier’s Conclusions! • Some organisms in the past differed greatly from any living species and that some organisms had become extinct. • The deeper rock layers hold fossils that are increasingly different from living species. • Cuvier came up with his idea of CATASTROPHISM.
Catastrophism • The idea that sudden geologic catastrophes caused the extinction of large groups of organisms at certain points in the past. • Cuvier’s idea of catastrophism helped scientists to accept the idea that geologic change and extinction had occurred.
Charles Lyell (Geologist) • Believed that geologic processes that have changed the shape of Earth’s surface in the past continue to work in the same ways. • Uniformitarianism: the idea that the forces that change the Earth’s surface in the past are still continue to work and change Earth’s surface in the same ways in the present.
So . . . Earlier Beliefs were Wrong . . . • Geologists give evidence that supports that Earth is older than only thousands of years. • Geologists give evidence that supports that the Earth continues to change under the same forces that existed in the past. • Scientists give evidence that species have changed over time by studying fossils. • Scientists give evidence that species that had existed on Earth became extinct.
Evolution • The development of new types of organisms from preexisting types of organisms over time. • Modern scientists also define evolution as a heritable change in the characteristics within a population from one generation to the next.
The Mechanism of Evolution • Scientists started to agree that organisms have changed over time - have evolved. • Scientists needed to find or explain how organisms change over time – they needed to find the mechanism of evolution!
Jean Baptiste Lamarck • Inheritance of acquired characteristics: Individuals could acquire traits during their lifetimes as a result of experience or behavior and pass these traits on to their offspring.
Charles Darwin • Described the process of evolution as “descent with modification.” • Darwin was not the first person to put forward the idea of descent with modification, but he was the first to argue that ALL species had descended from only one or a few original kinds of life.
Natural Selection • Darwin proposed the theory of Natural Selection as the mechanism for descent with modification. • The next ppt will discuss Natural Selection!
