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Selenium, which is an essential element for animals and prokaryotes and is a beneficial element for many plants, is the least-common of all the elements essential to life. [3] [63] Selenium acts as the catalytic center of several antioxidant enzymes, such as glutathione peroxidase, [11] and plays a wide variety of other biological roles.
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs .
List of elements by atomic properties; List of elements by stability of isotopes; A. Abundance of elements in Earth's crust; D. Discovery of chemical elements; M.
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
List of chemical elements — with basic properties like standard atomic weight, m.p., b.p., abundance; Abundance of the chemical elements; Abundances of the elements (data page) — Earth's crust, sea water, Sun and Solar System; Abundance of elements in Earth's crust
The classical elements typically refer to earth, water, air, fire, and (later) aether which were proposed to explain the nature and complexity of all matter in terms of simpler substances. [ 1 ] [ 2 ] Ancient cultures in Greece , Angola , Tibet , India , and Mali had similar lists which sometimes referred, in local languages, to "air" as "wind ...
All of these are elements of culture, broadly understood. Animals used in these ways include fish , crustaceans , insects , molluscs , mammals and birds . Economically, animals provide meat , whether farmed or hunted, and until the arrival of mechanised transport, terrestrial mammals provided a large part of the power used for work and transport.
A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient, [1] [2] but is also used to refer to minor elements in the composition of a rock, or other chemical substance. In nutrition, trace elements are classified into two groups: essential trace elements, and non-essential trace ...