BIO 311D 2nd Edition Lecture 37 Outline of Last Lecture I Introduction to Community Ecology II Biotic Interactions among species III In class exercise Yellowstone wolves Outline of Current Lecture I Biotic interactions II Yellowstone wolves Current Lecture I Biotic Interactions A Competition Seeking and using scare resources B 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 species C Gause s competitive exclusion principle Two species with identical niches cannot coexist 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 community b Includes 1 Its specific microhabitat and geographic range 2 Its activity period and seasonability 3 Its resources including role in the food web 4 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 invertebrates b What happened to the number of tide zone species present when Pisaster was removed 1 Remove Pisaster percent of species decreased greatly II c 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 biomass F Commensalism G Mutualism both organisms benefit from the interaction a Legume roots and nitrogen fixing bacteria b Termites and symbiotic protists and bacteria that digest cellulose c Acacia trees and ants that defend them d Leaf cutter ants and fungi e Lichens and mycorrhizae mutualisms are important everywhere H Parasitism Yellowstone Wolves A Wolves became extinct Female is the head of the pack Packs started being reintroduce into the community but also outside the community B Describe the wolf dispersion pattern in Yellowstone National Park They are separated by packs Each pack are territorial towards their area
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