Week 3 Notes
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This 3 page Class Notes was uploaded by Tara Dixon on Saturday September 10, 2016. The Class Notes belongs to Anthro2010 at Georgia State University taught by Bethany Lynn-Turner Livermore in Fall 2016. Since its upload, it has received 7 views.
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What is Karma?
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Date Created: 09/10/16
How do we define a Species?? 5 different ways of defining species 1. Biological 2. Typological 3. Mate recognition 4. Evolutionary species 5. Ecological **When Studying Macro Evolution we are looking at 3 variables 1. Rate of evolutionary change 2. Direction of the change 3. Effects of the change, whether that be speciation or not ***with micro- evolution no speciation occurs, with macro evolution speciation can occur OR larger scale taxa Species - Species – must be able to reproduce and produce viable offspring - a change in a species can be geographical/behavioral - Note example of horse/donkey: horse+donkey=mule, mule is not considered “species” bc a mule cannot produce offspring of its own , this demonstrates reproductive isolation, the horse/donkey are reproductively isolated from 1 another - Hybrids – evolutionary dead ends i.e. mule, hybrids can be sterile or reproductively viable, but the offspring i.e. the mule may not be able to reproduce therefore not carrying on its genes Type of Changes in species 1. Anagenesis – transformation of single species overtime “everyone is along for the ride,” it is a linear progression Ex: ABCD NOTE: B would not be able to reproduce with A, C could not reproduce with B and SO ON….. 2. Cladogenesis- formation of 1/more species from another species over time (branching out) **formation=speciation Ex: crocodiles, crocodiles are a species that is millions of years old but persist with species like humans that are only a couple hundred thousand years old, crocodiles and birds have common ancestry but they clearly do not look/ behave the same today Cladograms – discuss how distantly/recently species related to each other, but have no dates on them Contrast this with a Phylogeny – provides specific dates on when species began to diverge Things to NOTE: 1. Natural selection – only mechanism of adaptation 2. Fitness – survival/reproductive success 3. Evolution – change in allele frequencies in a population overtime 4. The idea of progress does not exist in evolution 5. The idea of primitive is always contrasted with derived, primitive means “old” in evolutionary biological terms; it is not contrasted with modern/good/new etc. Allopatric vs. Parapatric vs. Sympatric speciation: 1. Allopatric - barrier forms, separating 2 populations , genes cannot be spread 2. Parapatric – no real barrier to gene flow, but populations do not mate randomly, more likely with geographic neighbors than with a neighbor on other side of population’s range, divergence can occur from this with reduced gene flow 3. Sympatric – single species evolves from another species while inhabiting same geographic region Cladistics - Grouping only by shared, derived, homologous traits Homologous traits – shared b/c represent descent from common ancestor Ex: bat/bird wing Homoplasy – traits shared by different species through indpt. Evolution, evolved from separate alleles from separate genes What is Adaptation? - Feature/trait that enhances fitness - Natural selection is the ONLY mechanism for adaptation - Vestigial structures are example of adaptations…vestigial structures are present in humans but are no longer needed for our survival/reproductive success ex: appendix/wisdom teeth/tailbone 3 types of Adaptation 1. Stabilizing – favors average individual phenotype in a population, decrease in genetic variance 2. Directional –a population’s genetic variance shifts towards a new phenotype whenever the environment changes i.e. the pepper moths in England, they changed from light to dark as their environment changed from light colored trees to dark colored trees, moths used trees as camouflage 3. Diversifying(disruptive) – average phenotypes are not as “fit” (fit meaning successful reproduction/survival) as extreme phenotypes Categories of Adaptation 1. Adaptation – feature produced by natural selection for “current” use 2. Exaptation – feature performs function diff. from its original purpose ex: narwhal (narwhale) has a very long incisor tooth that resembles a horn, it was previously used as a tooth but is now used to attract mates 3. Pre-adaptation – a feature works well in one function on one organism, later discovered to work well in another function on another organism EX: the dinosaur, the dinosaur was recently discovered to have feathers, they used these for thermoregulation, dinosaur feathers were precursors to bird feathers, but birds use feathers to FLY today, while the dinosaurs used them for the thermoregulation Limitations of Adaptations 1. Time lag – selective pressures > the effects of natural selection 2. Historical/phylogenetic constraints – must work with what you have 3. Genetic variability – mutations are COMPLETELY RANDOM