The diversity of life on Earth is a result of the dynamic interplay between genetic opportunity, metabolic capability, environmental challenges, and symbiosis. For most of its existence, Earth's habitable environment has been dominated by microorganisms and subjected to their metabolism and evolution. As a consequence of these microbial activities, the physical-chemical environment on Earth has been changing on a geologic time scale, thereby affecting the path of evolution of subsequent life. For example, the release of molecular oxygen by cyanobacteria as a by-product of photosynthesis induced global changes in the Earth's environment. Since oxygen was toxic to most life on Earth at the time, this posed novel evolutionary challenges, and ultimately resulted in the formation of our planet's major animal and plant species. This interplay between organisms and their environment is an inherent feature of living systems.
All life forms require certain core chemical elements needed for biochemical functioning. These include carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—the elemental macronutrients for all organisms—often represented by the acronym CHNOPS. Together these make up nucleic acids, proteins and lipids, the bulk of living matter. Five of these six elements comprise the chemical components of DNA, the exception being sulfur. The latter is a component of the amino acids cysteine and methionine. The most biologically abundant of these elements is carbon, which has the desirable attribute of forming multiple, stable covalent bonds. This allows carbon-based (organic) molecules to form an immense variety of chemical arrangements. Alternative hypothetical types of biochemistry have been proposed that eliminate one or more of these elements, swap out an element for one not on the list, or change required chiralities or other chemical properties.
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Other articles related to "conditions, condition":
... Conditions are usually extended regular expressions, although there are other forms of condition also ...
... its existence is dependent on external conditions ... Everything is in constant flux, and so conditions and the thing itself is constantly changing ... that phenomena arise and cease according to (complex) conditions ...
... Instrument meteorological conditions (IMC) is an aviation flight category that describes weather conditions that require pilots to fly primarily by ... Pilots sometimes train to fly in these conditions with the aid of products like Foggles, specialized glasses that restrict outside vision, forcing the student to rely on instrument indications only ... The weather conditions required for flight under VFR are known as Visual Meteorological Conditions (VMC) ...
... The weather in Antarctica can be highly variable, and the weather conditions can often change dramatically in short periods of time ... There are three classifications for describing weather conditions in Antarctica ... Condition 1 Windspeed over 55 knots (60 miles per hour) Visibility less than 100 feet (30 meters) Wind chill below −100 °F (−73 °C) Description Dangerous ...
... The method is the collection of conditions in which the GC operates for a given analysis ... Method development is the process of determining what conditions are adequate and/or ideal for the analysis required ... Conditions which can be varied to accommodate a required analysis include inlet temperature, detector temperature, column temperature and temperature program, carrier ...
Famous quotes containing the word conditions:
“The depth and strength of a human character are defined by its moral reserves. People reveal themselves completely only when they are thrown out of the customary conditions of their life, for only then do they have to fall back on their reserves.”
—Leon Trotsky (18791940)
“The Settlement ... is an experimental effort to aid in the solution of the social and industrial problems which are engendered by the modern conditions of life in a great city. It insists that these problems are not confined to any one portion of the city. It is an attempt to relieve, at the same time, the overaccumulation at one end of society and the destitution at the other ...”
—Jane Addams (18601935)
“In a country where misery and want were the foundation of the social structure, famine was periodic, death from starvation common, disease pervasive, thievery normal, and graft and corruption taken for granted, the elimination of these conditions in Communist China is so striking that negative aspects of the new rule fade in relative importance.”
—Barbara Tuchman (19121989)