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Anthroguide(2) - Chapter 5 Macroevolution"Evolution above...

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Chapter 5 Macroevolution “Evolution above the species level”. Focuses upon the formation of new species (speciation) and on the evolutionary relationships between groups of species. Speciation – the process of forming new species. Cladogenesis - “speciation through a branching mechanism whereby an ancestral population gives rise to two or more descendant populations” Anagenesis - a sustained directional shift in a population’s average characteristics o Ex. A single population accumulates sufficient new mutations over time to be considered a separate species. Genetic drift - random loss in alleles over time (change in a genetic make up of a population over time) o Random changes in the gene pool o Population bottleneck o Gamete Sampling o Founder Effect o Population Bottleneck o Catastrophic event kills most individuals of population; most genetic diversity is lost This leads to the “Large genetic diversity in the original population” to “population’s gene pool is forced in a ‘bottleneck’”. This leads to “the population size rebounds, but with a fraction of the original genetic diversity” Gamete Sampling o Genes are passed to new generation in frequencies unlike those of past generations o Recessive genes are not masked Founder Effect o Fission of a population from leads leads to two or more genetically distinct separate populations One population => splits, turns into two or more. Ex: Take our anthropology class, split it in the middle. Left and Right sides start own colonies. The genetic gene flow will look different from both sides o Lots of variations vs. less variation Darwinian gradualism - Speciation through adaptation (long periods of transition) Punctuated equilibria - Stephen Jay Gould and Niles Eldredge: i. Marcroevolution occurs via long periods of stability or stasis punctuated by periods of rapid change Continential drift - according to the theory of plate tectonics, the movement of continents embedded in underlying plates on the earth’s surface in relation to one another over the history of life on earth. Hominoids – humans, chimps, bonobos, and gorillas o Hominid – inside the bush (particular critters that have certain traits that make then more human than hominoids)
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Hominids o Hominids are those hominoids that are in the fossil record that are bipedal o Not all hominids are necessarily human ancestors (but may share common ancestor) Bipedalism – walking of two legs as opposed to four (quadripedalism). Preceded large brains. HUMAN PHYLOGENY Piltdown Man – Found in 1912, Sussex England. Had a very large brain, but an ape like jaw. In the 1950’s, the hoax was uncovered. It was a human skull with an ape jaw attached – this took a lot of time to make it look authentic.
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