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The USDA's original food pyramid, from 1992 to 2005 [1] A food pyramid is a representation of the optimal number of servings to be eaten each day from each of the basic food groups. [2] The first pyramid was published in Sweden in 1974. [3] [4] [5] The 1992 pyramid introduced by the United States Department of Agriculture (USDA) was called the
In order to more efficiently show the quantity of organisms at each trophic level, these food chains are then organized into trophic pyramids. [1] The arrows in the food chain show that the energy flow is unidirectional, with the head of an arrow indicating the direction of energy flow; energy is lost as heat at each step along the way. [2] [3]
Charles Elton subsequently pioneered the concept of food cycles, food chains, and food size in his classical 1927 book "Animal Ecology"; Elton's 'food cycle' was replaced by 'food web' in a subsequent ecological text. [96] After Charles Elton's use of food webs in his 1927 synthesis, [97] they became a central concept in the field of ecology.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
A pyramid of energy shows how much energy is retained in the form of new biomass from each trophic level, while a pyramid of biomass shows how much biomass (the amount of living or organic matter present in an organism) is present in the organisms. There is also a pyramid of numbers representing the number of individual organisms at each ...
[6] [12] In terms of a food web, a cycle or loop is defined as "a directed sequence of one or more links starting from, and ending at, the same species." [ 13 ] : 185 An example of this is the microbial food web in the ocean, where "bacteria are exploited, and controlled, by protozoa, including heterotrophic microflagellates which are in turn ...