Biology 1B, Ecology Lecture 5, Page 1 Professor Resh • Spring 2008*Assigned readings, 7th Edition pp. 1083-1093, 1159-11716th Edition pp. 1096-1100, 1174-1186Organism Interactions and CompetitionOutline of Lecture 5A. Competition1. Competitive exclusion2. Competition between two speciesB. Limiting resourcesC. Competition1. Exploitative competition2. Interference competitionD. Demonstrations of interspecificcompetition1. Tribolium beetles2. BarnaclesA. Competition: the use or attempted use ofa limited environment resource by two ormore populations (interspecific) or bymembers of the same population(intraspecific).1. Competitive exclusion: if twospecies are competing for the samelimited resource, one species will beable to use that resource moreefficiently than the other and theformer species will be able toeliminate the latter species locally.2. Competition between two species islikely to be more intense, the moresimilar their ecological requirements;species occupying similar niches willtend to evolve in ways to minimizecompetition. Niche: sum total of allecological needs and tolerances.Biology 1B, Ecology Lecture 5, Page 2 Professor Resh • Spring 2008*Assigned readings, 7th Edition pp. 1083-1093, 1159-11716th Edition pp. 1096-1100, 1174-1186Organism Interactions and CompetitionB. Limiting resources1. Energy2. Nutrients3. Water space4. Nesting sites5. RefugiaC. Competition (N1 and N2 populations)dN1=N1r1K – N1 – (α x N2)dt Kalso,dN2=N2r2K – N2 – (β x N1)dt KCompetition cont’dwhen N1 is the size of competing population 1,N2, is competing population 2, α is theproportional effect on species 2 on the populationsize of species 1 relative to resource K, and β isthe effect of species 1 on species 2. α and β tend(but not always) to be reciprocal. For example:Cockroaches A= 0.001 B=100 CompetitionGorillas 1.0 1.0 Species 1 Species 2Elephants 100.0 0.001 intraspecific intraspecificInterspecificBiology 1B, Ecology Lecture 5, Page 3 Professor Resh • Spring 2008*Assigned readings, 7th Edition pp. 1083-1093, 1159-11716th Edition pp. 1096-1100, 1174-1186Organism Interactions and Competition1. Exploitative competition: twoindividuals are using the same limitedresource in the same way but havedifferent efficiencies in using thatresource. There are no directinteractions.2. Interference competition:competition results from directbehavioral interactions.E. Demonstrations of interspecificcompetition1. Tribolium flour beetles (hot anddamp, T. castaneum thrives; cool anddry, T. confusum thrives).2. Barnacles: species A lives in shallowwater, often exposed to air; species Blives in deeper water, rarely exposedto air.a. In deeper water, species B outcompetes species A; but if species Bis removed, species A moves intodeeper zone.b. In shallow water, remove species Abut species B cannot tolerate shallowwater conditions.c. Hence they are only competing indeeper
View Full Document
Unlocking...