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50/50. Over 20 generations all populations were either 100% red or 100% brown—this is genetic drift due to small population size so either allele becomes fixed in each instance.Island Populations-Factors affecting island populations:oSmall population sizeoFew foundersoHigher probability of extinction and loss of alleles-Thus if we surveyed island pops around world relative to mainland sources, the island pops are less genetically diverse due to genetic drift. Thus genetic drift leads to loss of genetic diversity. Mainland populations have more
genetic diversity than island populations-Founder effect: Silver Eye: the birds on the mainland have more genetic diversity than the ones on the islands, and the ones on the smaller islands have even less than that of the larger islandsMigration (Immigration and Emigration)-Migration: a change in gene frequency in a population due to the influx and/or outflux of individualsoIf migrants are a non-random subset of the population, evolutionis likely. For example, individuals with larger wings are more likely to disperseoIn small populations:The loss/gain of a few individuals can substantially change allele frequency (genetic drift)Nonrandom migration in combination with drift could also cause substantial gene frequency change (Small populations with 10 or 20 individuals and a handful of large winged individuals leave, this can have a tremendous impact of allele frequency.)oEX: Glanville fritillary: FMR is directly proportional to dispersal ability: the higher the FMR the more energy the butterflies can use towards flight. Isolated populations are more likely to be founded by PGI-F allele individuals because they can fly farther distances.Consequences of evolutionary change:-1) impact other species in community-2) other species evolve in response-Coevolution: reciprocal evolution in 2 populations or speciesoTypes of interactions:oPredator-preyEX: co-evolution b/w predators and prey: It was found that with regard to gastropod families, we start to see appearance ofgastropods with thicker shells. It’s argued that the thickening of the shells is a defense against crushing predators: crabs/lobsters. This is directional NS, leading to increased fitness due to thicker shells.Shell thickness has increased overtime. But after looking at predator record, there was an increase in claw size. So as the gastropods evolved to have thicker shells, the crabs/lobsters also evolved to have larger claws. THUS: this is a great example of co-evolution of predators and prey. Also an example of an evolutionary arms-race.oCompetitor-competitor: coevolution occurs between species which share the same limiting resource--2 competitors.oPlant-herbivoreoMutualists
Population Ecology-Populations- a group of individuals of a single species at a particular space and timeoOrganisms which have the potential to interactand interbreedoPopulations are the level at which NS and evolution operate—evolution does not act on individuals, it acts on populations-Populations are subdivided into demes, or subpopulations. Demes are linked