Biology Notes - Evolution and Population
Biology Notes - Evolution and Population Bio 1130
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This 5 page Class Notes was uploaded by Tasha Nelson on Monday September 5, 2016. The Class Notes belongs to Bio 1130 at East Tennessee State University taught by Jennifer Price in Fall 2016. Since its upload, it has received 69 views. For similar materials see Biology for Science Majors 3 in Biology at East Tennessee State University.
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Date Created: 09/05/16
8/23/16 What is evolution? Genetic Change in a population of organisms. Generally leads to progressive change from simple to complex. A widely used term which refers to how an entity changes through time. What is population? A group of organsims of the same species living in the same place. Metapopulation? A population of populations, or a group of groups, that is made up of the same species. Each subpopulation or subgroup is seoerated from all other subpopulations. But movement of undividuals from one population to another occurs regularly. Species: Morphological species concept Biological species concept Phylogenetic species concept. Important when studying evolutionary concepts. Legal aspects: U.S endangered Species Act of 1973 Convention on International trade in Endangered Species. (CITIES) Biological Species Definition: Actually or potentially interbreeding populations. Produce viable and fertile offspring GENE FLOW Reproductively isolated from other groups. Not based on similarity or appearance. ESA Definition: Species any subspecies of fish or wildlike or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature. Observable facts: Organisms produce more offspring that the environment can support. (Some will dies early) There are differences amont individuals which affect their ability to survive and or reproduce. Some of that variation is heritable Given enough time these small changes accumulating each generation can account for the variation we observe among the type of organisms we see todauy. Natural Selection: Overproduction of offspring each generation. (Some will die) Variation in ‘fitness’ that is heritable Those with higher fitness will be more represented in the next gen. Selection is a result: Given these conditions, populations evolve. There is no plan behind it, it just happens Was a controversial idea: Mostly inference that results of a selection would account for variation observed today Also very simple and logical. 8/25/16 A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. If enough evidence is accumulated in support of a hypothesis it moves to a THEORY in the scientific method and becomes accepted as a valid explanation of a phenomenon. Scientific Method: observation, hypothesis, experiment,data, reproduce Microevolution Process of biological change The Modern Synthesis and HardyWeinburg The Modern Synthesis Combines evolutionary theory with genetics Darwin did not know about Mendels worl It existed at his time, but was not well known Today we know that populations evolve when the proportions of alleles change Microevolution: Changes in the proportions of alleles in a population over time. Mutations in alleles are permanent. IF it is not permanent then it is NOT a mutation. New allele combinations are introduced by crossing over, or recombination. The environment determines if a mutation is good or bad. If it helps the species to be more genetically fit then it is a good one. If it hinders the survival then it is bad. Genetic diversity: GD refers to the variation or variety of genes (alleles) within a species. Important because: Rate of evolutionary changes in a population is proportional to the amount of genetic diversity available. High GD = high indiv fitness Global GD represents all of the info for all bio processes on the planet Genetic variation IS the heritable variation Darwin wrote about. Remember populations evolve. Indiv do not. For a pop to evolve there must be a GV among the indiv. Adaptation – Verb: the process by which benifitial traits are acquired by a population. Noun: A trati that enhances the survival or reproductive ability of those possessing it. (fitness) Allele frequency is the propotion of all alleles of a gene that there are a certain type of. AA aa Aa Level of heterozygosity is how many different types of a particular gene exist. Heterozygosity = GV Heterosis: The enhancement of fitness due to increased heterozygosity (GV) What is the link between heterzygosity and fitness? Not well understood but some possibilities: Overdominance (balanced polymorphism) Some cases the heterozygous genotype is most fit. Ex: Sickle cell. Those who have it are immune to malaria Single Nucleotide Polymorphism (SNPs) : Single base differences that exist in a population at a frequency greater than 1% Measure of GV ( look at class notes for examples on determining GV probabilities) The gene pool: The sum of all the alleles in a population Alleles are contained in diploid individs Populations acts like a bad of alleles from gen to gen There are 5 condition s for hardy Weinberg equilibrium 1. Randon mating ( with respect to the gene in question) 2. In infinite population size 3. No migration between populations 4. No mutation 5. No selection ( on the gene in question) FOR THE EXAM Be able to calculate allele, genotype and phenotype proportions. Go back and forth from umbers to props Predict genotype props from HW Use HW to estimate allele, genotype props form phenotypes Assumptions of Random Mating Individs do not select mates on the basis of the character in question They may choose mates based on other characters that are unlinked to the one we care about. NonRandom mating: Positive assortment Indivisuals choose mates with traits SIMILAR to their own. Negative Assortment Individs choose mates with traits DISSIMILAR to their own. Results of POS assormtnet – More homozygotes (fewer heterozygotes) than is predicted by HW The population acts like two separate pops. Over time can lead to isolation and new species Assortment does NOT have to be absolute… a simple trend can have an effect Results of NEG assortment More heterozygotes than is predicted by HW The population is more likely to stay together Individs are more genetically diverse may be an advantage (disease resistnace) Again, assortment does not have to be absolute..simple trend can have an effect. Testing if a population is in HW equilibrium. pay attention to whether you are being asked for actual ( observed) genotype props or HW predicted (expected) genotype props. If you have nimbers of actual genotypes, or phenotypes of a CODOMINANT gene you can calculate actual genotype props If you only have phenotypes in a dominant gene, you can only calc predicted genotype props. GENOTYPE PROPS MAY OR MAY NOT BE IN HQ EQUILIBRIUM