APY 203 Ch 5 text notes & Lecture: MACROEVOLUTION
APY 203 Ch 5 text notes & Lecture: MACROEVOLUTION APY 203
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This 3 page Class Notes was uploaded by Demaree Rios on Tuesday February 2, 2016. The Class Notes belongs to APY 203 at University of Miami taught by William Pestle in Spring 2016. Since its upload, it has received 36 views. For similar materials see Principles of Physical Anthropology in anthropology, evolution, sphr at University of Miami.
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Date Created: 02/02/16
CHAPTER 5 NOTES: MACROEVOLUTION ➢ ORGANIZING ORGANISMS ○ taxonomy: the field that establishes rules for classification ○ classificati ordering organisms into categories, shows evolutionary relationships such as: ■ forelimb development in vertebrates ■ basic genetic regulatory mechanisms relatively unchanged in animals for millions of years ■ essential genetic foundation for macroevo. change ○ homologies: structures shared by a species based on descent from a common ancestor ○ analogie: similarities between organisms based only on common function (ex. butterflies have wings and so do birds), similarities are a product of independent adaptation not common evolutionary descent ○ homoplasy: the separate evolutionary development of similar characteristics between different groups of organisms ➢ DEDUCING EVOLUTIONARY RELATIONSHIPS ○ evolutionary systematics: ■ analyzes homologous traits to connect organisms’ potential ancestors and descendants ■ phylogenetic tree:chart, incorporates aspect of time and implies ancestordescendant relationships ○ cladisti : ■ analyzes certain types of homologous characters(those which are more informative/recent traits) ■ ancestral traits: primitive traits a group of organisms inherited from a distance ancestor, usu. don’t supply enough info to make conclusions ■ clade: lineages that share a common ancestor ■ cladogram; chart, represents evolutionary relationships based solely on interpretation of shared derived characteristics (no time component nor ancestordescendant relationships) ● monophyletic: clade whose descendants all share common ancestor ● polyphyletic: clade whose descendants have more than one common ancestor, so not a true “clade” ○ shared derived: specific characteristics between 2 organisms considered most useful for evol. interpretations ➢ microevolution:small scale change gen to gen, of gene frequency, results in intro of new variety ➢ macroevolution: changes bring about new species ➢ SPECIES ○ biological species conc: a species is a group of individuals capable of fertile interbreeding with each other but reproductively isolated with other groups ○ speciatio: process by which a new species evolves from an earlier one, most basic process of macroevolution ■ geographic isolation: common mechanism that gives rise to speciation bc geographical barrier will limit gene flow within a population resulting in increasing genetic differences to the point of speciation ➢ WHAT EVOLUTION ISN’T ○ isn’t Lamarckian bc you can’t pick and choose, the idea that acquired characteristics are heritable (giraffes “passing on their stretched out necks” example) ○ isn’t random, some traits are advantages bc better suited not by accident bc it has been selected for over time ○ shouldn’t be thought of/ modeled as “linear progress” from simpler to more complex”better” life forms NO. think of a tree with many branches representing a diversity of life forms not a ladder ○ same for humans, human evo. is not human progress, the modern humans that exist today may be better suited for current environment but are not “better” than those that came before ○ isn’teleologica, isn’t goalorientated, organisms are not granted the things they need to solve environmental problems, rather, variation exists and over time better suited organisms come to dominate bc their traits of those environmental conditions are selected for ○ works on preexisting structures/processes (tinkering). ex. complex organs such as the eye ○ isn’t social, has nothing to do with lived experience of individuals, there is no social context ➢ WHAT EVOLUTION IS ○ change in gene freq (alleles) in a population over time ○ allele frequency ■ expression of % of various alleles for given trait in a given pop ■ frequencies always sum to 1.0 or 100% ■ trackable ○ the result of 5 factors that bring out change in allele freq. ■ mutation: the only way new variation can occur. alteration at genetic level of makeup of an organism. errors in DNA transcription (point mutation) in sex cell, something new may come about. chances are very very small, very rare event but still fundamental ■ gene flow: exchange of alleles between segments of a population. “where the soldiers go, the genes flow”. doesn’t introduce anything new just moves gene variants around ■ non random./assortative mating: mating is not random, you pick your mates (or who you don’t want to mate with) for certain reasons. choosing mates, inbreeding (makes recessive alleles more common) ■ genetic drift: random event, usually in small populations, full genetic frequencies thus are not represented bc of small pop. sample leading to little variation which could be dire if certain lvi is put under nat’l sel pressure. ex founder’s effect: random event when small group of ind found a new colony far away from original pop so the original high allele frequencies maintain high(. Bottleneck: small % of a pop survives, the pop. that reemerges is different from original pop. ■ natural selection: what acts on genetic variety and allows selected for to produce slightly more and not selected for slightly less, have more babies pass on moe gen material. fitness= net reproductive success. environment is key, species must be well suited for their env.favorable var. produce more offspring and have been historically better suited. nat’l selection selects for phenotypes (expression) but evolutionary consequences are seen on level of the genotype. ● directional selection: over time as a result of selective forces, variation in a pop will shift toward previously existing extremes ● stabilizing selection: being closest to the avg is the most advantageous ● disruptive selection, the mean is such a compromise that the mean isn't well suited for either of the tasks. important for macroevolution and speciation. somehow the two extremes are selected for and the median/ mean selected against ○ Evolution is result of 5 factors, genetic processes, descent with modification, takes place on a scale of pop, takes place over many generations= INDIVIDUAL ORGANISMS never evolve ➢ POPULATION GENETICS ○ allele freq proportion of a specific allele at given locus ○ genotype freq: proportion of a specific genotype at given locus ○ phenotype fre ○ to be able to see if evol IS occurring must consider what to expect if it weren't happening? ○ once know that know evol is occurring if we see departure of HE equil. ○ HardyWeinburg Equilibrium how alleles are distributed and how change over time. see changing in this equill. then know evol happening bcoe of these assumptions will be violated ■ assumes infinite pop size ■ no allele gene flow ■ no mutation ■ random mating ■ no selection Eqns: frequency can be expressed as decimal or % *once you know one (either p or q) it’s just simple algebra to figure out the other variable Allele Freq:Dominant allele freq = p Recessive allele freq = q p + q = 1 or 100% Genotype Freq: Homozygous Dominant = q² Heterozygous = 2pq Homozygous Recessive = p² q² + 2pq + p² = 1 or 100% Phenotype Freq: observable proportion of allele expression
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