Unit 3 Evolution Lecture 18 Intro to Evolution Section 22 1 22 2 Concepts Be able to explain the difference between natural selection and evolution Natural selection is a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits Evolution is descent with modification this is what Darwin first called evolution It is the idea that living species are descendants of ancestral species that were different form the present day ones It is also defined more narrowly as the change in the genetic composition of a population from generation to generation Evolution can be a pattern or a process The pattern of evolutionary change is revealed by data from many scientific disciplines while the process of evolution consists of the mechanisms that produce the observed pattern of change In summary evolution is the general process of change over time in whatever form while natural selection is the specific mechanism that Darwin is famous for discovering Be able to explain the basic principles of natural selection The basic principles of natural selection include variation overproduction adaptation and descent with modification Variation is defined as the heritable differences that exist in every population are the basis for natural selection Overproduction is the competition between offsprings for resources Adaptation is a trait that helps an organism survive and reproduce Descent with modification is that natural selection will result in species with adaptation that are well suited fro survival and reproduction In other words individuals show variation Variations can be inherited Organisms produce more offspring that can survive Variations that increase success will be more likely to be passed on to future generations Be able to distinguish between evolutionary change and other kinds of changes Evolutionary change is a gradual change in the characteristics of a population of animals or plants over successive generations This accounts for the origin of existing species from ancestors unlike them Know that evolution produces allele frequency changes inherited phenotypic changes differences among populations new phenotypes and new species and phylogenetic relationships Lecture 19 Evidence for Evolution and Modern Evolutionary Biology 22 2 22 3 Concepts Be able to describe the different types of evidence for evolution and explain their significance Life on Islands Fossil Record Observation of Natural Selection Artificial Selection Comparative Anatomy Convergent Forms Ontogeny Phylogeney Molecular Evolution Gene Homology Development and Evolution Terminology 1 Homology Similarity in characteristics resulting from a shared ancestory 2 Endemic Referring to a species that is confined to a specific geographic area 3 Fitness the idea that the fittest will go on this is related to natural selection 4 Convergence Related to convergent evolution the independent evolution of similar features in different lineages 5 Phylogeny the evolutionary history of a species or group of related species 6 Non coding DNA in genomics and related disciplines they are components of an organism s DNA that do not encode protein sequences Lecture 20 Evolution and Genetics 23 1 23 2 23 3 23 4 pg 479 481 Concepts Know that evolutionary change means genetic change Be able to calculate allele and genotype frequencies from genetic data To do this you will have to remember the formula P2 2pq q2 1 AND p q 1 p is the frequency of the dominant allele in the population q is the frequency of the recessive allele in the population p2 is the percentage of homozygous dominant individuals q2 is the percentage of homozygous recessive individuals 2pq is the percentage of heterozygous individuals Be able to explain that evolution can be described as change in allele frequency in a population Be able to explain how the Hardy Weinberg equilibrium shows that Mendelian inheritance will not change allele frequencies Mendelian rules of dominance and recessiveness has been used to predict the probability of an offspring genotypes for particular traits based on the known genotypes of their two parents The Hardy Weinberg equation allowed geneticists to do exactly this for entire populations Allele frequencies will remain unaltered indefinitely unless evolutionary mechanisms cause them to change Know that drift is genetic change due to random change Know that gene flow is genetic change due to movement among populations adaptive change Know that natural selection is the evolutionary force producing Know that natural selection can be stabilizing disruptive or directional Stabilizing natural selection is where the is a decrease of a population s genetic variance when natural selection favors an average phenotype and selects against extreme variations Directional selection is when a population s genetic variance shifts toward a new phenotype when exposed to environmental changes Diversifying or disruptive selection increases genetic variance when natural selection selects for two or more extreme phenotypes that each have specific advantages In diversifying or disruptive selection average or intermediate phenotypes are often less fit than either extreme phenotype and are unlikely to feature prominently in a population Terminology 1 Allele Frequency the relative frequency of an allele variant of a gene at a particular locus in a population expressed as a fraction or percentage Specifically it is the fraction of all chromosomes in the population that carry that allele 2 Hardy Weinberg equilibrium The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation provided that only Mendelian segregation and recombination of alleles are at work 3 Migration a regular long distance change in location 4 Genetic drift change events can also cause allele frequencies to fluctuate unpredictability from one generation to the next especially in small populations IMPORTANT THINGS TO NOTE FROM READING Effects of Genetic Drift 1 Genetic drift is significant in small populations Chance events can 2 Genetic drift can cause allele frequencies to change at random cause an allele to be disproportionately over or underrepresented in the next generation Although chance events occur in populations of all sizes they tend to alter allele frequencies substantially only in small populations Because of genetic drift an allele may increase in
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