Construction plan (morphology)

Construction plans in biology are mainly created in morphology (theory of forms) and used in taxonomy , systematics and comparative physiology . The common new and original characteristics of a systematic group ( taxon ) are represented in a construction plan .

General

The blueprint, especially in the case of higher taxa, does not have to resemble a single living organism, i.e. an individual of a species. Rather, it is more important that all original and new characteristics of a taxon are included in the blueprint that represent the common characteristics (homologies) of the species group shown. Features that only occur in individual sub-taxas as special developments or reductions are therefore not listed in the construction plan. Difficulties in creating a taxonomic blueprint are mainly caused by analogous structures, which in contrast to homologous structures have the same function, but do not have the same origin. The distinction between apomorphies (derived characteristics), plesiomorphies (inherited characteristics), synapomorphies (common derived characteristics) and symplesiomorphies (jointly inherited characteristics) is a major problem in the creation of building plans.

For research on evolution, research on tribal history and, in particular, systematics, "construction plans" are of particular importance. Early biology based its systematics exclusively on morphological blueprints. Only with the advent of genetics , in particular DNA sequence comparison (see genetic fingerprint , microsatellites , etc.), allozyme analysis and comparative behavioral biology since the middle of the 20th century, additional methods for systematic-taxonomic relationship analysis were developed. Many results of the morphological taxonomy were confirmed by the new methods and many cases of doubt were clarified.

Disciplines such as systematic palaeontology , which deals with extinct forms of life, of which often only impressions and fossils have survived, are still almost exclusively dependent on the morphological construction plan system.

History of the "blueprint" term

A sketch by Richard Owen from 1847. It shows his concept of archetypes for the vertebrates archetype for all vertebrates

Étienne Geoffroy Saint-Hilaire tried to analogize the body structure of vertebrates and invertebrates and thereby arrived at a theory of the unity of the building plan, unité de plan , a theory of the analogies (in current terminology also referred to as homologies ), from which he concluded that the Development of living beings can be derived from a single blueprint, plan d'organization . Because of this hypothesis he got into a dispute with Georges Cuvier , known as the Paris Academy dispute (1830-1832), who postulated a split into four different and independent basic plans in the animal kingdom. In the summer of 1831, Richard Owen accepted Georges Cuvier's invitation to Paris. He spent a month there. At the Jardin des Plantes he met Cuvier's patron Etienne Geoffroy Saint-Hilaire. Richard Owen developed an idea of a basic building plan for all vertebrates . He called this plan archetype .

literature

Thomas Junker: History of Biology: The Science of Life. Beck (2004) ISBN 3-4065-0834-0 p. 35 ff.