Which scientist developed the ‘key’ for identification of animals?

Concept: An identification key is the practical tool of taxonomy. It is a fixed series of paired, mutually exclusive statements about observable characters — each pair called a couplet — and at every step the observer picks the statement that matches the specimen, which leads either to the next couplet or to the name of the group. A key therefore does not create a classification; it is the step-by-step instrument that lets anyone reach an already-described taxon from characters alone.

Application: The stem asks who built such a character-by-character route for identifying animals. Among the names offered, the credit goes to John Ray (1627–1705), the English naturalist. In his systematic catalogues of animals — above all the Synopsis Methodica Animalium Quadrupedum et Serpentini Generis (1693), and the ornithology and ichthyology he completed with Francis Willughby — he sorted animals by successive contrasting external and anatomical characters such as the presence of hoofs, the number of toes and the form of the teeth, so that a specimen could be traced down the branching choices to its group. He also framed the first working biological definition of species, which gave those end-points a fixed meaning. This is the attribution carried by the official UPTET 2016 (Paper 2) answer key.

Cross-check — what each of the other names is credited with:

• Goethe: the theory of plant metamorphosis, which reads every floral organ as a modified leaf, plus comparative work on the vertebrate skull — morphology and theory, not a character-by-character identification route.

• Cuvier: the founding of comparative anatomy and vertebrate palaeontology and the principle of correlation of parts; he divided animals into four embranchements, which is a classification scheme rather than a stepwise identification tool.

• Theophrastus: the Historia Plantarum, which described and grouped about 500 kinds of plants and earned him the title Father of Botany — plant description in antiquity, and not about animals at all.

Note on the wider credit: histories of taxonomy often trace the first fully analytical dichotomous key to Jean-Baptiste Lamarck (Flore française, 1778). Lamarck is not among the names offered here, and of the four that are offered only John Ray is associated with character-by-character identification of animals, so he is the answer to this question.

Result: Among the offered names, the key for identification of animals is credited to John Ray.