Any of the sequential stages in a food chain, occupied by producers at the bottom and in turn by primary, secondary, and tertiary consumers. Decomposers (detritivores) are sometimes considered to occupy their own trophic level. ◇ The rate at which energy is transferred from one trophic level to the next is called the ecological efficiency. Consumers at each level convert an average of only about 10 percent of the chemical energy in their food to their own organic tissue. Since plants can only convert approximately 1 percent of incident sunlight into chemical energy at the lowest trophic level (the bottom of the food chain), the percentage of the energy in incident sunlight that reaches a tertiary consumer is about 0.0001.
step in a nutritive series, or food chain, of an ecosystem. The organisms of a chain are classified into these levels on the basis of their feeding behaviour. The first and lowest level contains the producers, green plants. The plants or their products are consumed by the second-level organisms-the herbivores, or plant eaters. At the third level, primary carnivores, or meat eaters, eat the herbivores; and at the fourth level, secondary carnivores eat the primary carnivores. These categories are not strictly defined, as many organisms feed on several trophic levels; for example, some carnivores also consume plant materials or carrion and are called omnivores, and some herbivores occasionally consume animal matter. A separate trophic level, the decomposers or transformers, consists of organisms such as bacteria and fungi that break down dead organisms and waste materials into nutrients usable by the producers
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