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Oxygen cycle refers to the movement of oxygen through the atmosphere (air), biosphere (plants and animals) and the lithosphere (the Earth’s crust). The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as well as how it is used. The oxygen cycle is the biogeochemical cycle of oxygen atoms between different ...
Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light or chemical compounds; the sources of carbon can be of organic or inorganic origin. [ 1] The terms aerobic respiration ...
Oxygen radical absorbance capacity ( ORAC) was a method of measuring antioxidant capacities in biological samples in vitro. [1] [2] Because no physiological proof in vivo existed in support of the free-radical theory or that ORAC provided information relevant to biological antioxidant potential, it was withdrawn in 2012. [3] [4]
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] In order to more efficiently show the ...
A heterotroph ( / ˈhɛtərəˌtroʊf, - ˌtrɒf /; [ 1][ 2] from Ancient Greek ἕτερος (héteros) 'other' and τροφή (trophḗ) 'nutrition') is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary ...
Oxygen began building up in the atmosphere at approximately 1.85 Ga. At current rates of primary production, today's concentration of oxygen could be produced by photosynthetic organisms in 2,000 years. [ 4] In the absence of plants, the rate of oxygen production by photosynthesis was slower in the Precambrian, and the concentrations of O 2 ...
Dead zone (ecology) Red circles show the location and size of many dead zones (in 2008). Black dots show dead zones of unknown size. The size and number of marine dead zones—areas where the deep water is so low in dissolved oxygen that sea creatures cannot survive (except for some specialized bacteria)—have grown in the past half-century.
Oxygen is a chemical element; it has symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is the most abundant element in Earth's crust, and after hydrogen and helium, it ...