EEB214H1 Lecture 19: The Great Wall of China

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Ecology & Evolutionary Biology
Jennifer Carpenter

EEB214 Lecture 19 The Great Wall of China • we can keep great walls or highways that keeps populations separated • which eventually can lead to speciation • Researchers sampled plants from either side of the wall in a variety of locations o Site B and Site C o count differences of every pair of individuals and build a tree o different DNA = far apart o the mountain path [Site C] has no impact of how much gene flow there is across o Site B [Great Wall] we see there’s two big groups ▪ much more likely to be related to someone from the same side as them o because: pollinators cannot move, or seeds cannot flow • Highways in California o we expect they work the same ways as the Great Wall because animals don’t want to cross highways o e.g., big horn sheep ▪ before highways –selection efficient and little drift ▪ There is less gene flow across highways ▪ if there’s a highway, then there is only 1.5-2 migrants every generation o no matter how far apart, highways are keeping the population constant o population close to each other—more migrants o the highways isn’t physically stopping the sheep but something about it has a significant impact of how many sheep is near by o when population is split, the smaller the population, the stronger the drift o drift strong = lose alleles and less diversity of alleles and cause them not to be as good as adapting to changes in environment What happens when genes don’t get along? • sexual conflict: male and female genomes have different fitness interest • Meiosis keeps most genes fair o any one allele has 50% chance of ending up in a gamete o if there’s some allele, they can affect this and make it bias which use it as an advantage to spread into the population • The Seven daughters of eve—book o see how closely related mitochondria are [several groups] o inherited through mom o test when the genotypes arose and where it spreads o look at the history of female migration • This means that mitochondrial gene have different fitness optima than the genome as a whole o the nuclear genome wants to have son and daughter but mitochondria only wants to have a daughter o if it’s in a son—fitness = 0 o When a plant is hermaphroditic it only passes its mitochondria on to half its offspring o if the orange plant always acts as a female then its mitochondria has maximized its fitness • Cytoplasmic Male Sterility (CMS) o mitochondria in male parts can poison them/turn itself off o alleles get into male parts and shut down so the cells cannot make pollen and get no energy o energy is to make female role o This decreases the fitness of the rest of the genome ▪ so nuclear genome will evolve a counter measure to restore hermaphroditism o a defence allele appears and protects the guys from mitochondria [if there is a female allele] ▪ everyone has a cure for the selfish mitochondria so it has no affect • What happens if you cross plants from different populations? o What sex might these offspring be?
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