Anthropology notes

Anthropology notes - 17/10/2007 22:28:00 Forces of...

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Unformatted text preview: 17/10/2007 22:28:00 Forces of evolution 1. Mutation 2. Genetic drift 3. Gene flow 4. Natural selection Mutation : change in DNA sequence of a gene due to random error Genetic drift : random change in allele frequency Gene flow : movement of genes from one population to another Natural selection : difference in levels of fitness depending on genotypes or phenotypes 1. Mutation: Source of all new genetic material in a species Must occur in a gamete to have evolutionary significance Most mutations have a detrimental effect and are weeded out by natural selection In some cases, mutations can be advantages Chromosomal mutation Monosomy: loss of a chromosome Trisomy : extra chromosome Klinefelters syndrome : XXY male thats infertile (a he-she) Point mutation : substitution of one base for another, which may produce a stop codon : o TTT- T AA-ATA o TTT- G AA-ATA o ACC-TTT-AT A o ACC-TTT-AT T 4. Natural selection: fitness relative change in the environment can change fitness Natural selection of simple traits: o Selection against one of the zygotes o Selection for heterozygotes (heterozygote advantage) o Sickle-cell o Genotypes: AA: normal As: reduced oxygen Ss: suffer from Sickle cell anemia o Selection for heterozygotes Balanced polymorphism Can either increase or decrease variation within population variation Natural selection is the only evolutionary force that has direct adaptive consequences It favors useful genes while eliminating deleterious ones Directional Selection: (e.g. increase in brain size in humans through time) selection against one extreme or the other o directional selection o causes a change in the mean Stabilizing selection: No major change in mean size Reduces variation Disruptive selection: Results in bimodal distribution Simple (Mendelian) traits: one gene = one trait Complex traits: polygenic traits o Pleiotropic traits Pleiotropic Traits: o PKU homozygotes dont produce enzyme that converts amino acid phenylalanine to tyrosine o Causes CNS damage o Dietary management can prevent damage o Other consequences of PKU: blue eyes, fair skin, light hair, all due to diminished ability to produce melanin. Macroevolution Occurs over many generations and focuses on major biological changes, such as speciation (e.g. homo sapiens) Hardy-Weinberg theory: Mathematical model that predicts the distribution of alleles in a population Identifies when a population is in genetic equilibrium...
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This note was uploaded on 04/18/2008 for the course ANTH 101 taught by Professor Streeter during the Spring '08 term at Boise State.

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Anthropology notes - 17/10/2007 22:28:00 Forces of...

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