Jan 29 Natural Selection Lab.pdf

Jan 29 Natural Selection Lab.pdf - Natural Selection...

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Natural Selection Lab (Darwins Postulates) In lecture, you have discussed some of Darwin’s theories on how populations evolve. D arwin’s Theory of Evolution was driven by natural selection. Darwin proposed four postulates that, if met would result in a change in the population over time resulting in the evolution of species due to natural selection. These postulates are: 1. There is variation within the species of interest 2. Some variation is passed on from parents to offspring 3. Some individuals are more successful at surviving and reproducing than others 4. Survival and reproduction are not random, instead they are due to the variation among individuals in the population Objective: We will experimentally manipulate a predator/prey study system (Rotifers/Yeast) to determine if Darwin’s four postulates are satisfied , which will theoretically allow evolution by natural selection to occur. The Yeast (The Prey): The yeast species we will be using is Saccharomyces cerevisiae (aka Brewer s yeast). This fungus is instrumental in making wine, baking, and brewing beer. This particular species has two different genotypes. One genotype is the wild type (a strain, gene, or characteristic that prevails among individuals in natural conditions) and produces a unicellular morph typically seen in the wild . The second genotype has a mutation which has knocked out the gene responsible for mother-daughter cell separation after mitosis. This leads to a phenotypic morph w ith “snowflake” clusters (multi cellular clusters). Yeast reproduce by budding. Mother cells that have the wild type genotype produce single- celled daughter cells. Mother cells that have the second genotype, the multicellular morph, produce offspring that share the same phenotype and become part of the yeast cluster.
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The Rotifer (The Predator): Rotifers are multicellular near-microscopic animals (Kingdom: Animalia) that are classified as their own invertebrate phylum (Rotifera). These organisms have complete
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