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Exam 1:What is evolution? Change in characteristics of a population over time- Allele frequency change: evolution at a specific gene (trophy hunting in rams with large horns caused small horns to increase in frequency)- Descent with modification: same as ancestors, but slightly different (natural selection is responsible for this)- Populations evolve, individuals do notWhat are the units of evolution? (what is it that evolutions acts upon). -natural selection: - Directional selection: individuals with one extreme of phenotypic traitare favored over others (large over medium and small)- Stabilizing selection: intermediate phenotype are favored over others (medium over large and small)- Disruptive selection: phenotypes at either ends of extreme are favored over intermediates (large and small favored over medium-beetles) -mutation: change in DNA caused by copying errors during cell division, mechanical damage when molecules collide with DNA, exposure to mutagens,and exposure to radiation, very rare -Genetic drift: chance events, catastrophic events- Can either increase or decrease genetic variation, can possibly increase a harmful allele (prairie chicken: due to farming, numbers decreased, reduced genetic variation, eggs failed to hatch, genetic driftled to the fixation of harmful alleles)- Bottleneck effect: reduction of population due to environmental events (earthquakes, floods, fires etc)- Founder effect: loss of genetic variation when a new population is formed by a small number of individuals from a larger population-gene flow: transfer of alleles from 1 population to another via the movementof individuals- Can introduce new alleles into a population- Makes populations genetically similar to one another, limit adaptation- Prevent 2 subpopulations from becoming 2 different species-Natural Selection – how it works? Who proposed it first? -the process by which individuals with certain heritable characteristics survive and reproduce more successfully than others because of those characteristics- Charles DarwinWhat is trait-matching? What mechanism produces trait-matching?- Adaptive evolution: process of change in which traits that confer survival or reproduction advantages tend to increase frequency over time (bird beak length with flower length)Heritability – what is it? Why is it important for evolution? How we can measure it?- Proportion of observable differences in a trait between individuals of the same population that is due to genetic differences- Measured by estimating relative contributions of genetic and non-genetic differences to the total phenotypic variation in a population- Differences in individuals causes natural selection and evolutionSexual selection - Intra: within, competition between the same sex, males fighting for women (big antlers, big teeth, claws, weaponry)- Inter: between, competition between opposite sexes, no fighting, dancing, bright plumage (peacock)Phenotype: the observable trait, determined by the genotypes interaction with the environmentGenotype: genetic makeup, one inherited from father and one from mother (AA, Aa,aa), combination of allelesAlleles: versions of genes that differ in nucleotide sequence, results in productions of different versions of protein that the gene encodesSources of genetic variety: - Point: nucleotide substitution- Synonymous: silent, no amino acid change- Nonsynonymous: amino acid alteringo Missense: from one amino acid to anothero Nonsense: sense stop codon- Insertion: addition of nucleotides- Deletion: removal of nucleotidesMutagens- Radiation: x-rays, gamma rays, alpha particles, uv light- Chemical: coal tars, radon gas, alkaloids- Biological: viruses, bacteria, transpoonsSomatic cell mutations: not inheritedRecombination: source of variation, crossing over during meiosisPlasticity vs. Adaptation: how we can tease them apart?- Plasticity: ability of an organism to change its phenotype in response to a change in its environment without changes in genotype, different phenotypesare not genetically different- Adaptation: trait that increases the ability of an individual to survive and reproduce compared to individuals without the trait and occurs on evolutionary time scales (changes at population level)Be prepared to answer some basic questions about mendelian genetics.Genetic Drift: chance events, catastrophic events- Can either increase or decrease genetic variation, can possibly increase a harmful allele (prairie chicken: due to farming, numbers decreased, reduced genetic variation, eggs failed to hatch, genetic drift led to the fixation of harmful alleles)- Bottleneck effect: reduction of population due to environmental events (earthquakes, floods, fires etc)- Founder effect: loss of genetic variation when a new population is formed by a small number of individuals from a larger populationDo natural selection produces perfectly adapted organisms? noSpeciation: evolve into different speciesHox genes and body plan.- HOX genes: determine basic features as where wings and legs will develop ona bird or how a flowers parts are arranged- Provide positional information during development- Evolution of vertebrates from invertebrates is associated with alterations in HOX genesEvolutionary radiation: increase in diversity due to adaptive radiation (anolis lizards in the caribbeanSympatric and allopatric speciation- Allopatric: gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations (squirrels at grand canyon)- Sympatric: new species evolve while in the same region (lakes of eastern African ridge have high diversity of closely related cichlids, anoles)- Cichlids diversify following an island model- island that are rocky or sandy at bottom of lake- Predators reduce gene flow between rocky ridges, isolating populations- Sexual selection accelerates evolutionary change on color patternsIsolation mechanism (pre and post-zygotic)- Prezygotic barriers: block fertilization from occurring- Habitat isolation- Temporal isolation- Behavioral isolation- Mechanical isolation- Gametic isolation- Postzygotic bariers: prevent the hybrid zygote from developing into a viable fertile adult- reduced hybrid viability- reduced hybrid fertility- hybrid breakdownHybridization, hybrid breakdown, hybrid vigor.- Hybridization: mating organisms of different species to create a hybrid- Hybrid breakdown: hybrid is viable and fertile but future generations have problems- Hybrid vigor (heterosis):


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PSU BIOL 220W - Exam 1

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