Evidence_for_Evolution[1]

Evidence_for_Evolution[1] - Evidence for Evolution Natural...

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Evidence for Evolution
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Natural Selection Darwin proposed 4 steps for how Natural Selection drives evolution: 1. Individuals must be variable 2. Traits that are variable are heritable -- passed on to next generation 3. An excess of offspring is produced 4. Differential production or survival – linked to speciFc traits
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Topics of Today’s Lecture Darwin's concept of genetics-blending inheritance Mendel saves the day The source of genetic variation-mutations and genetic recombination Evidence for evolution from: artiFcial breeding, homology, embryology, the fossil record, experiments, molecular biology, etc.
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Darwin’s Theory of Evolution through Natural Selection had a big problem. Darwin didn’t have a clue about genetics! • He believed traits were inherited by blending the characteristics of Male and female parents together in their offspring. Thus, a yellow butterFy and a red butterFy should have orange offspring. The trait of yellowness and redness would be lost and offspring would express the mean condition. • This would greatly constrain the ability of natural selection to produce adaptations to new conditions
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Mendel provides the answer to Darwin’s problem. How are traits passed on? Not as Lamarck proposed-acquired characteristics from use and disuse Mendelian Genetics: Gregor Mendel, in 1854 carried out breeding experiments in a monastery using the garden pea Pisum sativum In 1865 Mendel reported his results, but his results were not widely read until the 1900's
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Genetic Information is passed on in discrete units How are traits passed on? Mendelian Genetics Experiment: smooth x wrinkled seeds. The f1: all smooth The f2: 3/4 smooth and 1/4 wrinkled. One of Mendel’s basic outcomes: Inheritance of genes is discrete, no mixing. Genetic variation is preserved from generation to generation
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Where does genetic variation come from? Mutations-”mistakes” in DNA replication Thomas Hunt Morgan winner of the 1933 Nobel Prize for his work on Drosophila Fruit fy genetics © Copyright California Institute of Technology
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Types of Mutations • Point mutation-change of as little as one base pair in a gene; effects range from none (neutral) to great. • Chromosomal mutations- duplication, deletion,
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Evidence_for_Evolution[1] - Evidence for Evolution Natural...

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