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Transcript of Ch25
![Page 1: Ch25](https://reader038.fdocuments.in/reader038/viewer/2022103016/55508d00b4c905a85c8b4e85/html5/thumbnails/1.jpg)
Evolution
Chapter 25
Great Idea:All life on Earth evolved from single-celled organisms by the process of
natural selection.
![Page 2: Ch25](https://reader038.fdocuments.in/reader038/viewer/2022103016/55508d00b4c905a85c8b4e85/html5/thumbnails/2.jpg)
Chapter Outline
• The Fact of Evolution
• Chemical Evolution
• Natural Selection and the Development of Complex Life
• The Evolution of Human Beings
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The Fact of Evolution
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The Fact of Evolution
• Evolution– Ongoing process of change
• Scientists accept evolution as fact– Debate various theories
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The Fossil Record
• Fossils– Organism’s hard parts preserved
•Turned to rock•Replaced by minerals
• Fossil record– Fossils found, catalogued, and analyzed
– Shows transitions– Incomplete
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The Fossil Record – cont.
• Three key ideas– Older fossils more different– Increasing complexity with time– Most species have gone extinct
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Wide Variety of Fossils
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Fossil Trilobites
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The Biochemical Evidence
• DNA– Evidence for evolution
– Changes slowly
– Also compare amino acid sequences•Cytochrome c
– Humans and chimps identical
– Rattlesnake 86% overlap
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Evidence from Anatomy:Vestigial Organs
• Vestigial organs– Internal features– No useful function
• Examples– Appendix: humans– Wings: penguins– Hind legs: whales
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Wings of a Penguin Are Vestigial Organs
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Chemical Evolution
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Chemical Evolution
• Chemical evolution– Process of combining rocks, water and gases
• Miller-Urey experiment• Formation of cell
– Still unknown
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Miller-Urey Experiment
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Black Smokers
• Black Smokers– Deep-ocean floor– Vents of mineral rich hot water– Diverse ecosystem
•Most primitive bacteria
• Hydrothermal zones– Site of life’s origin?
•Protected•Ideal chemical environment
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Black Smokers
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RNA Enzymes
• Early life was simpler– RNA catalyzed reactions– Created proteins– Proteins led to DNA
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The Window of Opportunity
• Chemical processes– Occurred rapidly
• Recent discoveries– Schopf
•Evidence of life 3.5 billion years ago
• First cell– 4.0-3.5 billion years ago
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The First Cell
• First cell– No competition
– Multiplied rapidly
• Special characteristics– 20 amino acids
![Page 20: Ch25](https://reader038.fdocuments.in/reader038/viewer/2022103016/55508d00b4c905a85c8b4e85/html5/thumbnails/20.jpg)
Science by the Numbers
• Cell division
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The Ongoing Process of Science
• Did life also originate on Mars?– Evidence from a meteorite
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Natural Selection and the Development of Complex Life
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Natural Selection
• Charles Darwin
• Natural Selection– Variation in populations
•Some variation heritable
– More individuals born than will survive
• Adaptation
• Artificial selection
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Dog Breeds
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Cobalt-Winged Parakeets
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Science in the Making
• The reception of Darwin’s theory– On the Origin of the Species
• Alfred Russell Wallace
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Charles Darwin
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The Story of Life
• First cell– Natural selection
•Mutations
• Mutations– Random– Most not beneficial
• Environment– Impacts evolution
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The Story of Life – cont.
• Eukaryotes• Colonies• Hard shell
– Cambrian explosion
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A Fossil Microbe
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Rock with Fossils
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Major Steps in the Evolution of Life
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Geological Time
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The Ongoing Process of Science
• The evolution of whales– What does the fossil record tell us?
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Mass Extinctions and the Rate of Evolution
• Rate of extinction– 10%-20% extinct in 5-6 million years
• Mass extinctions– 30%-90% extinct
• Mechanisms– Asteroid
• Evolution – Gradualism– Punctuated equilibrium
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Extinction Events
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Giant Crater near theYucatan Peninsula
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Chesapeake Bay Impact Drilling Site
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The Evolution of Human Beings
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“Lucy”
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Neanderthal Man
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Thinking More about Evolution
• Young-earth creationism
• Intelligent design