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Biology 2200- Equilibrium Theory

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BIOL 2200
Joseph Rasmussen

Biology 2200 th Nov.12 , 2013 Equilibrium Theory - Islands o Equilibrium Theory of Island Biogeography o MacArthur & Wilson o Concepts are similar to rates of colonization and rates of extinction o We are looking at several different species on islands o When there are few species on the islands, there is a high colonization rate o As the number of species increases, the colonization rate decreases o If there are few species, there is a low extinction rate o As the number of species increases, the extinction rate increases o One prediction was that there are different extinction rates for different size of islands  Larger islands should have a smaller extinction rate than a smaller island  Smaller islands have smaller populations  Equilibrium number of species on a larger island is larger than the equilibrium number of species on a smaller island o Colonization rates should be larger for larger islands than smaller islands o Islands closer to mainland will have more species compared to islands farther away from the mainland o Dan Simberloff  Figure 20.21  Results predicted were found  There were more species on the islands closer to the mainland than those farther away - Continents o More species fill up ecological niches and therefore extinction rate increases o With more species there is less room for a new species to come in and start a life Communities - Regional diversity is being driven by speciation - When species exchange, they sometimes end up with a new predator and can drive to species extinction Adaptations & Phylogenetics - What conditions for evolution? - Phylogenetic inertia  the influence of an ancestor on its descendants o Kangaroos are good grazing animals. They are able to get away when need be. o The organism on the right side of slide 13 is related to dolphins and whales. They have an additional hind fin that was lost down the line and so modern dolphins and whales do not have them. Biogeography - The histories of the species living in a region - Looking at long term patterns in evolution, speciation and extinction - Communities include recent adaptations and things that happened a long time ago History of the Earth - Approximately 4.5 billion years ago - We know we started with prokaryotes and then established eukaryotes - Organisms started developing hard exoskeletons which enhanced fossilization - The deeper you look at deposition the older the fossils will be - Putting fossils together we have been able to put together a geological time scale of interesting events that have occurred Continental Drift - We are currently moving west about 4cm/year - 250 Mya the continents were all together (Pangea) - They then began to break apart into two landmasses (Laurassia and Gondwana) - At one point Greenland was at the equator, it wasn’t covered in ice. It is now at higher latitudes and covered in ice. This is why fossils have been found on Greenland. Dispersal -
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