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Concepts: Evolution and Human Origins

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Genevieve Dewar

Concepts: Evolution and Human Origins -What is Evolution? How does it work? -Natural Selection -Survival of the fittest -Sexual selection -Inheritance of traits -Adaptation to the environment -Variation already exists **Evolution affects populations not individuals** What is a Species? -A group of creatures which breed together and produce viable and fertile offspring -May be quite similar in appearance(deer) or quite variable(dogs) -May all live in one part of the world (polar bears) or in many parts of the world (right whales) -Share behaviour traits relating to social groups, food pe History of Origins -James Ussher -Origin of the Earth & therefore humans based on his interpretation of the Bible. -ArchBishop Ussher (1650 AD) -October 23rd 4004BC -Later addition 9:00am Geology Contributes -Catastrophists -George Cuvier (1769 - 1832) -If only 6000 years old, then global and violent catastrophes to explain canyons, mountains. -Reverend Burner(1681AD) noted slow erosion? Water, wind, ice. Carolus Linneus (1758) -Comparative Biology -Categorizing the worlds plants & animals - 7 Basic layers or taxon levels -Kingdom, Phylum, Class, Order, Family, Genus, Species -Binomial system -Homo Sapiens ( wise man) Uniformitarianism -Buffon (1749 AD) “to learn about the earth, to study the earth” - processes are known, natural and observable. -Hutton (1788AD) slow working, uniform & natural processes = hundreds of thousands of years. -Lyell (1873AD) 100,000 years “The present is the key to the past” -Reverend Chalmer - Ussher was wrong, not the bible. Life on Earth had changed -Conclusion of the Enlightenment period -Fossils, Extinct animals, Strata & stratigraphy -1800’s the question changed to “How did the Earth/Species change?” End of the enlightenment period... -Colonization -Identified new people not mentioned in the Bible Archaelogy -Stone tools, “Thunderstones” or pre-metal stone ages? Lamarck - First mechanism -1. Adaptation to the environment -2. Progression towards perfection -3. Inheritance of acquired characteristics. Darwin & Wallace: Mechanism of Natural Selection -Natural Selection- variation already exists between individuals of the same species, allows for adaptation to changes in the environment -Survival of the Fittest & Sexual Selection - Those individuals that are by chance best adapted to an environment will have higher reproductive success -Increases the frequency of that trait within the species/population Darwin’s Finches -Change occurs as an adaptation to a changing local environment -Change works on the variation of traits already present in a population -No direction Natural Selection: Survival of the Fittest 1. Favourable variations promote survival of the individuals in whom they appear -Traits are inherited by their offspring, whose chances of survival are also better -Favourable variations eventually spread through the population. 2. Unfavourable variations don’t promote survival -May cause the individuals to die at an early age -MAy reduce the fertility of bearers, who have few offpsring -Either way, unfavourable variations tend to be removed from the population 3. For any species, natural forces act to favor the expansion of some traits and to favor the removal of other traits from future generations. ** Mechanism of Evolution Processes Of Evolution -Mutation **On individuals** -Genetic Flow **On gene pools/populations** -Genetic Drift **On gene pools/populations** Gregor Mendel (1822 - 1884) -Breeding experiments with pea plants -Traits in offspring are not passed solely by either parent -Traits are passed in small independant packages from both parents Breeding program: -Cross-bred green peas with green peas: -Offspring of any gen always had green peas -Cross-bred yellow peas with green peas -All offspring plants (f, generation) bore green peas. -Cross-bred green offspring(f, generation) -Some of their offspring plants (f2, generation) had green peas and some had yellow peas. -Ratio of green to yellow plants in f2 generation was always 3:1. *Second generation of the green/yellow peas crossed with another green pea resulted in a 3:1 ratio of green to yellow peas. -Each observed trait derives from a package of information (Gene) acquired by the individual at conception -For each trait, an individual possesses two genes: one from each parent -Two matching genes Homozygous state: For a given trait, individual receives the same gene form from parents, Green and Green. -The whole set of different forms for a given gene are known as alleles -Mendel’s peas had alternative genes or alleles for green seeds and for yellow seeds -Sometimes the yellow allele was expressed (appeared in the plant) -Sometimes the green allele was expressed. Dominant genes - alw
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