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BILDSTUDY4 - Lecture 5 Population Genetics part C Clicker...

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Lecture 5 Population Genetics part C Clicker Question: Negative frequency dependent selection maintains or increases variation within a population. Conservation and Genetic Drift: Genetic Drift can decrease variation in cases of the northern elephant seal where population is reduced to 20 individuals causing alleles to be lost. Gene Flow- movement of alleles between populations 1. The example of the blue tit bird in different environments of mainland with good/ bad hosts and island with bad host a. On mainland birds in bad hosts die off and extra birds from good host migrate to bad host [no time to adapt to bad host] b. On island birds in bad host adapt to the environment and gets into synch with the caterpillar abundance. c. Birds from good host migrating to bad host is an example of Gene flow 2. Gene flow is an homogenizing force [mixes things up until allele frequencies are the same across populations] Forces that influence the Hardy-Weinberg Equilibrium Selection, mutation, non-random mating, genetic drift, gene flow Lecture 6 Trees A Phylogeny- Evolutionary history of a group of species 1. Systematics- those who study the evolutionary relationships among organisms 2. Phylogeny tree – must be inferred and is a picture of phylogeny. History of Phylogeny where classification of organisms is very old 1. First categorized by Carolus Linneaus a. Kingdom, Phylum, Class, Order, Family, Genus, Sick b. Darwin stated that hierarchical classification reflects historical events i.e descent from a common ancestor 2. Node- branching point that represents common ancestor of lineages 3. Capital letters – Species; Time – axis 4. Sister Taxa- are 2 taxas that come from an immediate common ancestor i.e A & B
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1. Monophyletic- contain common ancestors and all descendants 2. Paraphyletic- contains common ancestor and some but not all descendants 3. Polyphyletic- taxa with different recent ancestor Reasons as to why characters can be shared by 2 or more species 1. Homology – similarity due to inheritance of traits. i.e limbs are homologous even though they look different since they are compose of same parts 2. Homoplasy- characteristics shared between 2 or more species which are not present in common ancestor a. Homoplasy is caused by convergent evolution- where independent evolution of same character occurs in 2 or more species[caused by similar environments i.e cactus in different deserts etc.]
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BILDSTUDY4 - Lecture 5 Population Genetics part C Clicker...

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