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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 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 ...
A food pyramid and a corresponding food web, demonstrating some of the simpler patterns in a food web A graphic representation of energy transfer between trophic layers in an ecosystem Energy flow is the flow of energy through living things within an ecosystem . [ 1 ]
Like many wetlands, some ecosystems do not organize as a strict pyramid because aquatic plants are less productive than long-lived terrestrial plants such as trees. Ecological trophic pyramids are typically one of three kinds: 1) pyramid of numbers, 2) pyramid of biomass, or 3) pyramid of energy. [6] Food webs have trophic levels and positions.
Energy pyramids, however, will always have an upright pyramid shape if all sources of food energy are included, since this is dictated by the second law of thermodynamics." [ 196 ] [ 197 ] Most organic matter produced is eventually consumed and respired to inorganic carbon .
The Energy Hierarchy is a classification of energy options, prioritised to assist progress towards a more sustainable energy system. It is a similar approach to the waste hierarchy for minimising resource depletion , and adopts a parallel sequence.
The curve represents the energy gain per cost (E) for adopting foraging strategy x. Energy gain per cost is the currency being optimized. The constraints of the system determine the shape of this curve. The optimal decision rule (x*) is the strategy for which the currency, energy gain per costs, is the greatest.
37% (absorbed photon energy) → 24% is lost due to wavelength-mismatch degradation to 700 nm energy, leaving; 28.2% (sunlight energy collected by chlorophyll) → 68% is lost in conversion of ATP and NADPH to d-glucose, leaving; 9% (collected as sugar) → 35–40% of sugar is recycled/consumed by the leaf in dark and photo-respiration, leaving