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A pyramid of energy or pyramid of productivity shows the production or turnover (the rate at which energy or mass is transferred from one trophic level to the next) of biomass at each trophic level. Instead of showing a single snapshot in time, productivity pyramids show the flow of energy through the food chain. Typical units are grams per ...
Energy flow is the flow of energy through living things within an ecosystem. [1] All living organisms can be organized into producers and consumers, and those producers and consumers can further be organized into a food chain. [2] [3] Each of the levels within the food chain is a trophic level. [1]
Decomposers are often left off food webs, but if included, they mark the end of a food chain. [6] Thus food chains start with primary producers and end with decay and decomposers. Since decomposers recycle nutrients, leaving them so they can be reused by primary producers, they are sometimes regarded as occupying their own trophic level. [7] [8]
Out of a total of 28,400 terawatt-hours (96.8 × 10 ^ 15 BTU) of energy used in the US in 1999, 10.5% was used in food production, [3] with the percentage accounting for food from both producer and primary consumer trophic levels. In comparing the cultivation of animals versus plants, there is a clear difference in magnitude of energy efficiency.
A simplified food web illustrating a three-trophic food chain (producers-herbivores-carnivores) linked to decomposers. The movement of mineral nutrients through the food chain, into the mineral nutrient pool, and back into the trophic system illustrates ecological recycling. The movement of energy, in contrast, is unidirectional and noncyclic ...
Nutrient cycle is more often used in direct reference to the idea of an intra-system cycle, where an ecosystem functions as a unit. From a practical point, it does not make sense to assess a terrestrial ecosystem by considering the full column of air above it as well as the great depths of Earth below it.
They are essential to digestion and are also affected by food that is consumed. Bacteria are essential for metabolizing food substrates and thereby increasing energy output, and produce a great variety of metabolites, including vitamins and short-chain fatty acids that contribute to the metabolism in a wide variety of ways. [96]
The microbial food web refers to the combined trophic interactions among microbes in aquatic environments. These microbes include viruses, bacteria, algae, heterotrophic protists (such as ciliates and flagellates). [1] In aquatic ecosystems, microbial food webs are essential because they form the basis for the cycling of nutrients and energy.