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In phylogenetics, a single-access key (also called dichotomous key, sequential key, analytical key, [1] or pathway key) is an identification key where the sequence and structure of identification steps is fixed by the author of the key. At each point in the decision process, multiple alternatives are offered, each leading to a result or a ...
In biology, an identification key, taxonomic key, or frequently just key, is a printed or computer-aided device that aids in the identification of biological organisms. Historically, the most common type of identification key is the dichotomous key , a type of single-access key which offers a fixed sequence of identification steps, each with ...
A branching identification key within taxonomy (the practice and science of categorization or classification), is a presentation form of a single-access key where the structure of the decision tree is displayed graphically as a branching structure, involving lines between items. [1]
Where possible, this is traditionally done using dichotomous keys. Keys are traditionally found in such works such as floras, field guides or monographs. Botanical or entomological keys have been coded as computer programs. Applications are even available now which use artificial intelligence to identify plants on the basis of photographs.
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).
In a terminal reticulation a single taxon or next-level-key is keyed out in several locations in the key. This type of reticulation is normally compatible with any printable presentation format of identification keys and normally does not require special precautions in software used for branching keys.
The dichotomous key to recognizing the genera included to the subfamily Laricoideae is relatively simple, since only three of them belong to it and one of these is deciduous. Below is reported the taxonomic identification scheme in the form of a table:
A rooted tree T that is a subgraph of some graph G is a normal tree if the ends of every T-path in G are comparable in this tree-order (Diestel 2005, p. 15). Rooted trees, often with an additional structure such as an ordering of the neighbors at each vertex, are a key data structure in computer science; see tree data structure.