BLG 151 Lecture Notes - Lecture 8: Nerve Net, Mesoderm, Cnidaria
29 Sep 2017
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Animals are the only multicellular heterotrophs on the tree of life that ingest their food. Dipoblasts = animals whose embryos have two types of tissue. In general, the ectoderm produces the covering of the animal and the endoderm generates the digestive tract. Mesoderm gives rise to the tissues in between. Two groups of animals have been recognized as dipoblasts: the cnidaria (jellyfish, corals) and the. Nerve net = nerve cells that are organized into a diffuse arrangement. Radial symmetry = have at least two planes of symmetry. Usually float in water or live attached to a substrate. Tend to have long narrow body: radially symmetric organisms are equally likely to encounter prey and other aspects of the environment in any direction. As a result, a diffuse nerve net can receive and send signals efficiently: bilaterally symmetric organisms tend to encounter prey and other aspects of the environment at one end.
