Dichotomy

Dichotomy [ Biology ]
Adjective: Dichotomous or Dichotomic
Adverb: Dichotomously
Noun: Dichotomousness

Dictionary of botanic terminology
index of names


	In a broad sense dichotomy is a split or division into two non-overlapping or mutually exclusive parts or classifications.

Dichotomy [ Botany ]

In botany a dichotomy is the successive division and subdivision, as of a stem or branch of a plant or a vein of the body, into two parts as it proceeds from its origin; a successive bifurcation.

Strombocactus disciformis forma dicotomica

The place where a stem or vein is forked.

For example (photo at left) a dichotomously branched specimen of Stombocactus disciformis.

See also: Polytomy

Dichotomy [ Taxonomy ]


	In taxonomy a dichotomy is a division or distribution of genera into two species a division into two subordinate parts.

Such dichotomies are used as part of the process of classifying species, to build a taxonomic key. When classifying, a series of questions is asked which narrows down what is being examined, to indicate where it belongs in the hierarchy.
An example of dichotomy is the question "does it have a glochids?", used to divide the cactus species into plants belonging to the Opuntioideae subfamily ( with glochids) and into other subfamily of Cactaceae (Glochid-less).

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