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Edward Hitchcock's fold-out paleontological chart in his 1840 Elementary Geology. Although tree-like diagrams have long been used to organise knowledge, and although branching diagrams known as claves ("keys") were omnipresent in eighteenth-century natural history, it appears that the earliest tree diagram of natural order was the 1801 "Arbre botanique" (Botanical Tree) of the French ...
An evolutionarily significant unit (ESU) is a population of organisms that is considered distinct for purposes of conservation. Delineating ESUs is important when considering conservation action. An ESU is not always equivalent to a biological species but can be also a subspecies, variety, geographic race, or population.
An operational taxonomic unit (OTU) is an operational definition used to classify groups of closely related individuals. The term was originally introduced in 1963 by Robert R. Sokal and Peter H. A. Sneath in the context of numerical taxonomy , where an "operational taxonomic unit" is simply the group of organisms currently being studied. [ 1 ]
Biology is the scientific study of life. [1] [2] [3] It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. [1] [2] [3] For instance, all organisms are composed of at least one cell that processes hereditary information encoded in genes, which
It was a small, lizard-like animal, about 20 to 30 centimetres (7.9 to 11.8 in) long, with numerous sharp teeth indicating an insectivorous diet. [40] Other examples include Westlothiana (for the moment considered a reptiliomorph rather than a true amniote ) [ 41 ] and Paleothyris , both of similar build and presumably similar habit.
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [1] [2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [3] Cell biology is the study of the structural and functional ...
In biology, a motor unit is made up of a motor neuron and all of the skeletal muscle fibers innervated by the neuron's axon terminals, including the neuromuscular junctions between the neuron and the fibres. [1] Groups of motor units often work together as a motor pool to coordinate the contractions of a single muscle.
Human Sar1A bound to GDP. The COPII coat consists of an inner layer – a flexible meshwork of Sar1, Sec23, and Sec24 – and an outer layer made of Sec13 and Sec31. [1] Sar1 resembles other Ras-family GTPases, with a core of six beta strands flanked by three alpha helices, and two flexible "switch domains".