BIO120H1 Lecture Notes - Lecture 23: Detritivore, Herbivore, Ecological Network
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BIO120H1 Full Course Notes
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Direct and indirect interactions embedded in food webs; trophic cascades. Insect-plant relationships often specialized, so vertebrate-plant relationships less so. Tertiary consumers = carnivores who eat secondary consumers. Food chains and food webs: who eats whom, where does energy flow. Tropic connections among species can be analyzed as interaction webs with network properties like connectance . More importantly, trophic relations can determine community structure in ways that can be investigated by removal experiments. Hairston, smith and slobodkin (1960): trophic cascades the world is green because carnivores keep down herbivores so they don"t limit plant growth. Example of an indirect effect: one tropic level exerts influence on a second by affecting a third. Cascades involve effects that alternate across trophic levels. Trophic cascades likely, but can"t answer from topology of the food web alone . A: lizards do benefit plants because of unequal interaction strengths. But the effect of lizards on spiders is weak, while their effect on herbivores is strong.
