Student_Outline_Unit_3_starr Fall 2007

Student_Outline_Unit_3_starr Fall 2007 - Unit III...

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Unit III Evolution/Diversity Processes of Evolution In 17 th , 18 th century Europe—almost everyone believed in Creationism and that the earth was 6,000 years old (which was worked out as an estimate by Archbishop James Ussher in 1650). I. Natural Selection (NS) “Descent with modification” A. 3 key observations by Darwin: 1. Species tend to: over-reproduce (superfecundity) 2. Individuals in a population: vary extensively 3. Many varying traits: were inherited B. Conclusion – the varied traits that an individual inherits affects this individual’s ability to: Secure limited resources to better survive and reproducein particular environments Traits that are “better” than others for a particular environment become: more prevalent in future generations (micro- evolution) C. Darwin’s theory (published book: 1859 Origin of Species)- Diverse forms of life have arisen: from ancestral species by his theory of natural selection; “descent with modification” 1
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D. Natural Selection (NS) = Differential reproductive success __. In other words, individuals whose characteristics best adapt them to their CURRENT environment are most likely to survive and reproduce and pass along their genes _. 1. Successful or “fit” individual = one that survives and passes along his genes 2. Example of NS that has occurred: camouflage 3. Example of NS in action: DDT insecticide resistance 2
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E. Three key points about NS 1. NS is an editing _ process, not a creative process. What does this REALLY mean? 2. NS is contingent on: the particular environment; time and place 3. Significant evolutionary change can occur in a short _ time. END OF EXAM 2 MATERIAL II. Population Genetics Charles Darwin – In 1859, published theory of NS , without knowing about inherited traits/genes ( Gregor Mendel – 1860’s his work was not recognized until 40 years after the Origin of Species was published). Darwin, therefore, did not understand WHERE the variation of individuals came from. Interestingly, Darwin’s theory was attacked because of the lack of understanding of genes—it was argued that if two animals were blended (like horse and zebra) traits would be diluted and offspring would never have clear advantages.) Darwin was so unsure that he even stopped arguing his theory! A. = Modern synthesis (1940’s)- The ideas of Mendel _ and Darwin _ together. How is it different from Darwin’s theory of NS? 3
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1. It recognizes several processes of: evolution; not just natural selection; also: gene flow, mutation, genetic drift 2. It recognizes that “traits”: are genes that follow Mendelian rules B. NS acts on _*an individual*_ but the effect is a change in the population _. C. Population : individuals of the same species living at the same time in the same place D. Gene Pool - the sum of all alleles in a population E. Microevolution allele frequencies change over time F. What creates NEW alleles? mutations: the only way to CREATE a new allele 1. Lethal – lead to death in the individual 2. Neutral – has no effect in the CURRENT environment 4
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III. Hardy-Weinberg model of a non-evolving
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Student_Outline_Unit_3_starr Fall 2007 - Unit III...

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