BIO 311D 2nd Edition Lecture 37 Outline of Last Lecture I. Introduction to Community EcologyII. Biotic Interactions among speciesIII. In-class exercise: Yellowstone wolves Outline of Current Lecture I. Biotic interactionsII. Yellowstone wolvesCurrent LectureI. Biotic Interactions A. Competition: Seeking and using scare resourcesB. What is the effect of interspecific competition?a. The actual niche of the barnacle species was different from its fundamental (possible) niche because of competition with another speciesC. Gause’s competitive exclusion principle: Two species with identical niches cannotcoexist indefinitely. How could that be tested?a. Grow them separately then grow them together. Population density decreases when they’re in mixed populations b. Under experimental conditions, limiting the resources we are able to conclude that two species cannot live under the same niche D. What is a species “ecological niche”?a. The sum total of a species’ use of biotic and abiotic resources in its communityb. Includes:1. Its specific microhabitat and geographic range2. Its activity period and seasonability3. Its resources, including role in the food web4. Interactions with competitors, mutualists E. How could you test whether predators are regulating prey populations?a. The starfish Pisaster prefers to eat mussels but will feed on other invertebratesb. What happened to the number of tide zone species present when Pisaster was removed?1. Remove Pisaster: percent of species decreased greatlyc. Keystone species: are not abundant but exert strong control on the community, out of proportion to their number (e.g. sea otter – keystone predator)d. Dominant species: has the greatest biomassF. Commensalism G. Mutualism: both organisms benefit from the interactiona. Legume roots and nitrogen-fixing bacteriab. Termites and symbiotic protists and bacteria that digest cellulosec. Acacia trees and ants that defend themd. Leaf cutter ants and fungie. Lichens and mycorrhizae mutualisms are important everywhereH. Parasitism II. Yellowstone WolvesA. Wolves became extinct. Female is the head of the pack. Packs started being reintroduce into the community, but also outside the communityB. Describe the wolf dispersion pattern in Yellowstone National Park. They are separated by packs. Each pack are territorial towards their
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