Week 3 Notes
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This 2 page Class Notes was uploaded by Amanda Notetaker on Sunday February 7, 2016. The Class Notes belongs to 012 at University of Vermont taught by Dr. Hill in Fall 2016. Since its upload, it has received 31 views. For similar materials see Exploring Biology in Biomedical Engineering at University of Vermont.
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Date Created: 02/07/16
CH. 15 Processes of Evolution 15.1: Evolution is Both Factual & the Basis of Broader Theory Fitness: relative # of offspring contributed to the next generation by an individual Descent w/ Modification: (Darwin) change passed on through generations Evolution: (as defined by book) change in genetic composition of populations over time - Population: group of individuals of a species that live/interbreed in a specific geographic area at same time - Individuals do not evolve, populations do! Types of Evolution Adaptive: presence/absence of trait increase the fitness of an individual/population (trait evolves through natural selection) Non-adaptive: presence/absence of trait does NOT increase the fitness Evidence of Evolution Occurring: 1. Variation: provides variable traits (raw materials) - Due to cross over, mutations, migration/gene flow 2. Selection: chooses which traits get passed on creating a biased representation of trait within a generation (traits that increase in frequency are being selected) - Natural selection does not need to occur for evolution to be occurring 3. Inheritability: trait passed on to next generation (without inheritance there is no evolution) Ex: When flies are in a natural vs. artificial environment, both environments have evolution occurring b/c evolution doesn’t always occur based on “survival of the fittest” Charles Darwin - Lyell: Earth is slowly changing over time (geological theory of catastrophism vs. gradual change, uniformitarianism) - Malthus: resources grow linearly while population grows exponentially à “point of crisis” - Thoughts which helped Darwin: 1. Earth is very old/change is consistently occurring 2. Resources are finite/controls populations 3. There’s a great amount of diversity - Wallace and him both independently came up with the concept of natural selection 15.2: Mutation, Selection, Gene Flow, Genetic Drift, and Nonrandom Mating Result in Evolution Causes of Genetic Variation: mutation, selection (nonrandom mating), gene flow, genetic drift Mutation: any change in nucleotide sequences that occurs randomly w/ respect to organism’s needs (most basic origin of variation) - Natural selection influences random variation à adaptation - Can be deleterious (results in decreased fitness), beneficial, or neutral (no effect) - Rates of mutation vary; As genome size decreases, mutation rate usually increases - Cause different alleles to exist at a locus Gene Pool: sum of all alleles at all loci in a population Types of Selection: Natural: environment determines distribution/abundance of a trait; results in traits that help organisms survive/increase fitness (removes deleterious) Artificial: results in traits preferred by humans Sexual: mate choice determines Random: (Genetic Drift) random events determine (Ex: disasters, gamete unions, etc) Adaptation: favored trait that evolves through natural selection (removes deleterious mutations) Gene Flow: migration of individuals/movement of gametes between populations can change allele frequencies Allele Frequency: proportion of each allele in gene pool (unpaired alleles) Genotype Frequency: proportion of each genotype among the individuals in a population (pairs) Genetic Drift: random changes in allele frequencies from one generation to the next - Can change frequencies in small populations - Can change frequencies of neutral alleles in large populations Population Bottleneck: environmental event results in survival of only a few individuals - Can lead to genetic drift/changing allele frequencies - Populations don’t always lose genetic variation
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