Ecosystem Functions Three levels of organisms regulate the flow of energy in ecosystems: the producers , the consumers , and the decomposers . They are organized in complex food webs . Autotrophs — plants, algae, and some bacteria—are the primary producers of an ecosystem. Heterotrophs — animals, fungi, most protists and bacteria, and a few non-green plants—are the consumers in ecosystems. They obtain their energy and carbon from the organic material produced by the autotrophs. Four trophic (feeding) levels are recognized: The primary producers constitute the first level, followed by three levels of consumers. Primary consumers are the herbivores (plant eaters) that feed directly on the primary producers. The next level includes flesh-eaters, the primary carnivores that consume the herbivores. The top or fourth level is that of the secondary carnivores
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This note was uploaded on 11/14/2011 for the course BIO 1421 taught by Professor Farr during the Fall '08 term at Texas State.