Biology 1B Ecology Lecture 5 Page 1 Assigned readings 7th Edition pp 1083 1093 1159 1171 6th Edition pp 1096 1100 1174 1186 Organism Interactions and Competition Outline of Lecture 5 A Competition 1 Competitive exclusion 2 Competition between two species B Limiting resources C Competition 1 Exploitative competition 2 Interference competition D Demonstrations of interspecific competition 1 Tribolium beetles 2 Barnacles A Competition the use or attempted use of a limited environment resource by two or more populations interspecific or by members of the same population intraspecific 1 Competitive exclusion if two species are competing for the same limited resource one species will be able to use that resource more efficiently than the other and the former species will be able to eliminate the latter species locally 2 Competition between two species is likely to be more intense the more similar their ecological requirements species occupying similar niches will tend to evolve in ways to minimize competition Niche sum total of all ecological needs and tolerances Professor Resh Spring 2008 Biology 1B Ecology Lecture 5 Page 2 Assigned readings 7th Edition pp 1083 1093 1159 1171 6th Edition pp 1096 1100 1174 1186 Organism Interactions and Competition B Limiting resources 1 Energy 2 Nutrients 3 Water space 4 Nesting sites 5 Refugia C Competition N1 and N2 populations dN1 dt N1r1 K N1 x N2 K N2r2 K N2 x N1 K also dN2 dt Competition cont d when N1 is the size of competing population 1 N2 is competing population 2 is the proportional effect on species 2 on the population size of species 1 relative to resource K and is the effect of species 1 on species 2 and tend but not always to be reciprocal For example Cockroaches Gorillas Elephants A 0 001 B 100 1 0 1 0 100 0 0 001 Competition Species 1 Species 2 intraspecific intraspecific Interspecific Professor Resh Spring 2008 Biology 1B Ecology Lecture 5 Page 3 Assigned readings 7th Edition pp 1083 1093 1159 1171 6th Edition pp 1096 1100 1174 1186 Organism Interactions and Competition 1 Exploitative competition two individuals are using the same limited resource in the same way but have different efficiencies in using that resource There are no direct interactions 2 Interference competition competition results from direct behavioral interactions E Demonstrations of interspecific competition 1 Tribolium flour beetles hot and damp T castaneum thrives cool and dry T confusum thrives 2 Barnacles species A lives in shallow water often exposed to air species B lives in deeper water rarely exposed to air a b c In deeper water species B out competes species A but if species B is removed species A moves into deeper zone In shallow water remove species A but species B cannot tolerate shallow water conditions Hence they are only competing in deeper waters Professor Resh Spring 2008
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