Lecture 4 - Chapter 22 - The Case For and Against Evolution

Lecture 4 - Chapter 22 - The Case For and Against Evolution...

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1 1 4. Lecture 4 (today) - draft lecture posted last night, w/ caveat - revised lecture on BB now Announcements: 2. Quiz 1 - keys posted in back of room and on BB - comments on technical issues - comments on Quiz taking strategies 3. Lecture 3 -can ±d iscount ±s l ides not covered (> #34) - revised lecture posted on BB 1. Blackboard access 2 Myth #5 Evolution is a theory about the origin of life (continuation of Lecture 3) 3 Darwin did believe that all organisms on Earth trace their origin to a single ancestor However, he was not at all clear on how life itself originated 4 The Case For and Against Evolution Ch. 22 "Both sides ought to be properly taught . . .
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2 5 6 7 Does evolution provide a better description of the history of life on earth than competing descriptions? Evidence for Evolution 8 “Nothing in biology makes sense except In the light of evolution -Theodosius Dobzhansky, 1973 BISC 120
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3 9 History of Life on Earth Species change over time Branching of lineages Extinction Mechanisms Natural Selection (Darwin) Shifting Balance Theory of Evolution (Wright) Neutral Theory of Molecular Evolution (Kimura) Species change over time No branching of lineages No extinction Mechanisms internal forces inheritance of acquired characters Species fixed over time No branching of lineages No extinction Mechanisms -none (there is nothing to explain) Evolution (Darwin) Transformism (Lamark) Separate Creation Review of the 3 descriptions With extinction Without extinction Form -> Time -> 10 http://www.youtube.com/watch?v=R_RXX7pntr8 11 Rebuttal: Mutations are random (mostly). Selection is not. 12 Arguments against evolution
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4 13 Argument 1 : Evolution cannot be observed and therefore cannot be proved 14 Rebuttal: Evolution is observed all the time! 15 Rebuttal cont’d: We cannot observe the entirety of evolution and therefore rely on diverse lines of evidence, just as we do in other fields of science 16 Argument 2: There are no transitional fossils “…Why, if species have descended from other species by fine gradations, do we not everywhere see innumerable transitional forms?” -from The Origin chapter entitled Difficulties on Theory
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5 17 These fossils offer compelling evidence for descent with modification Rebuttal: The fossil record is spotty, but there are transitional forms 18 Ex)Transition between fish and amphibians Acanthostega 19 E.g.) Transition between bird and reptile Archeopteryx 20 e.g.) Transitions between horse species When fossils arranged by age, a progressive series of changes are seen.
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6 21 Again, the fossil record shows intermediate forms are possible Whale evolution 22 e.g.) Transition from terrestrial ancestor to whale (transitional fossils) 23
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This note was uploaded on 10/03/2009 for the course BISC 120 at USC.

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Lecture 4 - Chapter 22 - The Case For and Against Evolution...

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