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 not What are the units of evolution what is it that evolutions acts upon natural selection Directional selection individuals with one extreme of phenotypic trait are 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 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 population gene flow transfer of alleles from 1 population to another via the movement of 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 Darwin What 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 evolution Sexual 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 environment Genotype genetic makeup one inherited from father and one from mother AA Aa aa combination of alleles Alleles versions of genes that differ in nucleotide sequence results in productions of different versions of protein that the gene encodes Sources of genetic variety Point nucleotide substitution Synonymous silent no amino acid change Nonsynonymous amino acid altering o Missense from one amino acid to another o Nonsense sense stop codon Insertion addition of nucleotides Deletion removal of nucleotides Mutagens Radiation x rays gamma rays alpha particles uv light Chemical coal tars radon gas alkaloids Biological viruses bacteria transpoons Somatic cell mutations not inherited Recombination source of variation crossing over during meiosis Plasticity 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 phenotypes are 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 population Do natural selection produces perfectly adapted organisms no Speciation evolve into different species Hox genes and body plan HOX genes determine basic features as where wings and legs will develop on a bird or how a flowers parts are arranged Provide positional information during development Evolution of vertebrates from invertebrates is associated with alterations in HOX genes Evolutionary radiation increase in diversity due to adaptive radiation anolis lizards in the caribbean Sympatric 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 patterns Isolation mechanism pre and post zygotic Prezygotic barriers block fertilization from occurring Habitat isolation Temporal isolation Behavioral isolation Mechanical isolation Gametic isolation reduced hybrid viability reduced hybrid fertility hybrid breakdown Postzygotic bariers prevent the hybrid zygote from developing into a viable fertile adult Hybridization 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 Hybrid vigor heterosis improved or increased function of some quality in a problems hybrid Evolution by changes in gene expression heterochrony paedomorphosis heterochrony developmental change in timing of events that leads to