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Unformatted text preview: Population diversity, migration, and environmental diversity. From genetic diversity to human variation.--Evolution as change in the genetic makeups of populations--How do genetic changes get passed from one individual (parent) to another (offspring)--Mendelian genetics= Gregor Mendel was an Australian monk who during the years of 1856 to 1868 performed experiments of ordinary garden peas…results published in 1866--He found that if he crossed a red flowered pea with a white flowered peas, the first generation was all red (F1 100% red). But the second generation (F2 Generation 75% red, 25% white) the next generation had 3 red offspring and 1 white offspring Example From Cavalli-Sforza-- Mutations= random change to the DNA structure or genetic code. One mechanism for genetic diversity to occur. Mutations are usually deleterious and do not get passed on to the next generation because offspring die before the age of reproduction. However some diseases do not occur until after the reproductive age and can get passed to offspring.--Example: Thallassemia or Mediterranean anemia affecting the red blood cells.--N=normal; T=mutation that causes anemia: N T >>N NN-normal NT-sick >> NT-sick TT-lethal--75% NORMAL (1 HOMOZYGOUS, 2 HETEROZYGOUS)--25% DISEASED (1 homozygous)--Heterozygous individuals have an advantage when affected by malaria--Natural selection favors the NT individuals in areas with malaria. Thus they continue to produce in the population at large. How and Why are Genetic Changes Expressed in a Population-- Three factors that make individuals and populations different biologically--mutation=random change to the DNA structure or genetic code--Natural Selection= the survival of the fittest. Acts on traits that benefit the adaptation of the species to their environment.--Genetic drift=changes in the gene pool purely as a result of chance, and not as a result of selection, mutation, or migration Natural Selection-- The Theory of Evolution by Natural Selection formulated by Charls Darwin published “The origin of Species” in 1859-- Darwin and Wallace recognized the heritable variation as characters passed on by the parents. However, they did not know of Mendel’s work in which it was recognized that the unit of selection was the gene that behaves in a predictable manner--They observed the persistence of characters that benefited the adaptation of the species to their environment--Wallace and Darwin recognized the gradualism of environmental change--Evolution by means of natural selection was for Darwin and Wallace just the differential reproductive success of the species and the adaptation to changing environments where adaptive characters are perpetuated and non-adaptive one are eliminated Darwin and Wallace’s Evolutionary Process--Every species on this planet arose through the same process--This process defines why a species looks and behaves a certain way. This process affects their morphology, physiology, and behavior--Humans are subject to the same evolutionary process...
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This note was uploaded on 02/12/2012 for the course BT 1003 taught by Professor As during the Spring '11 term at American Jewish University.
- Spring '11