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Lecture 5

Lecture 5 Notes.pdf

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Hannah Holmes

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Lecture 5 September-20-11 12:51 PM Darwin realized what was happening in the artificial setting was also happening in the real setting (i.e. plant and pigeon breeders) artificial selection -cabbage varieties Broccoli comes from the flower Brussel sprouts comes from the shoots kohlrabi comes from the stems artificial selection - tomatoes gene fw2.2 -- reduces cell Researchers took a sibling plant, division, the wild type. and then inputted the fw2.2 Breeders have selected for a gene.. researchers were able to genetically unmanipulated grow a smaller tomato (resembles domestic tomato.. so it's the smaller, wild-type tomato) bigger Has to do with when and where it is expressed -- with reference to coding and regulatory region of the gene In evolution: Changes occur due to Regulatory region responsible for changes in regulation of the gene, not turning on and off the gene the protein (bias) natural selection - orange hot chili peppers There's variation amount If something's increasing linearly and individuals in population. Red something's increasing exponentially -- indicates spicy flavour (capsacin). eventually the exponential will always The plant from which the chili was outnumber. Therefore, populations will obtained had very low levels of always outnumber number of resources. capsacin (white) and high levels (red) We expect mild chilis are going to lose out b/c mice eat them. This leaves us with just The variation is inherited (if two the spicier individuals. mild individuals.. they can produce mild offspring) and two spicy individuals produce strong The outcome results in mostly hot chilis. individuals. We're assuming mouse eats a certain More individuals are born than phenotype and that's encoded by a will survive to reproduction. genotype Fitness: We usually don't measure the fitness of an individual. We should think of an individual as an average individual of the population. Microevolutionary -- we're concerned with everything about populations and Sometimesindividuals are below protective of their relatives as well. natural selection - "Darwin's finches" Finches have been very well studied. Among the living species we see enormous phenotype difference with respect to beaks. Researchers are unable to resolve the difference between each column. With more data we can resolve this. natural selection - Grants' finches The Grants' have spend 40 years studying finches on Galapagos islands Every year they try to tag every individual of all finches on the island every year They tag them so they can look at them from binoculars and then they know their info They caught natural selection in action We have the beak depth on the x-axis -- ranges from 6 -14 mm There is variation postulate 1: variation among individuals We take a mother and father bird and average their beak depths Then we look at all of their offspring and we take average Beak depth is heritable, but not value of their beak depth 100% heritable Then we get 1 pt for each parent and offspring There is some scatter, but there's a best fit line postulate 2: trait properties are heritable From 1976 to 1977, a decrease in finches. Where we see a decline in number of individuals we also see decline in number of seeds for Haven't identified a si
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