title: Neural nets.
abstract: Although modern evolutionary biology has abandoned the use of 'lower' or 'higher' for animals, the quote of G.H. Parker captures quite well the current understanding of the nerve net as the evolutionarily oldest organization of the nervous system, the major organ system responsible for processing information and coordinating animal behaviour. The degree of complexity of a nervous system - in particular its organization into substructures such as brains and nerve cords - shows fascinating variations between animals. Even within an individual, the nervous system can show parallel existing types of organizations that are only partially connected, illustrated by the well-known central and peripheral nervous system. In general, the architecture of the nervous system is adapted to the specific needs and lifestyle of the individual species. How these diverse and complex nervous systems evolved is an ongoing debate among zoologists and evolutionary biologists.
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008 Bergen, Norway. Electronic address: andreas.hejnol@uib.no.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hejnol
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008 Bergen, Norway. Electronic address: fabian.rentzsch@uib.no.
authors.forename: Fabian
authors.initials: F
authors.lastname: Rentzsch
mesh_terms: D000818:Animals; D005075:Biological Evolution; D047108:Embryonic Development; D009415:Nerve Net / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development / Q000502:physiology*; D010802:Phylogeny