BIOL150 Chapter Notes - Chapter 12: Decomposer, Primary Producers
14 Sep 2018
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Among the secondary producers, first-level consumers (herbivores), second trophic level; and second-level consumers (first-order carnivores), third trophic level. Grazing food chain: the herbivores are biophagus that consume living plant biomass. Detrital (decomposer) food chain: the herbivores are saprophagus that consume dead organic matter (detritus) Herbivores in each chain are the energy source for carnivores, and the source of energy for the detrital chain is dead organic matter and wastes from the grazing food chain. Energy is not recycled in the detrital chain, because the second law of thermodynamics states that energy can only flow one way. However, the detrital food chain can recycle its matter until it is all used up, whereas the grazing food chain which involves only living tissues, cannot. The distinction between grazer and detrital food chains is blurred at higher trophic levels because even highly selective carnivores rarely distinguish whether their prey are members of a grazing or a detrital food chain.
