BIOL 2P92 Lecture Notes - Lecture 11: Platyzoa, Mesozoa, Acoelomorpha
6 Feb 2017
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Document Summary
No adaptive significance of spiral vs. radial cleavage. Protostome (3) vs. deuterostome: deuterostome: mouth developing second after blastopore becomes the anus, protostome: mouth develops first after blastopore invagination. Coelom have been emphasized as an important trait that differentiates the clades of animals: development of coelom appears to have been a result of convergent evolution. 3 body plans, formerly thought to represent shared ancestry, now known to be polyphyletic or convergent. Platyhelminthes = serious parasites of humans and animals associated with humans. Most well-known are the planarians: mouth and head at different places mouth in the middle of the body, light sensitive, many live in water, some are terrestrial, zooids become individuals when fragmented. Has a lumen: space inside a cell or organ. Has a cellular digestive system, and therefore there is no anus. Has a well-developed nervous system: ganglia = groups of cells of neurons; kind of like a small brain.
