Biology 3229F/G Lecture Notes - Lecture 11: Tusk Shell, No Brain, Giant Squid
10 Dec 2016
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7 classes of living mollusca 100 000 species. Directly below arthropods for greatest number of species. Chordata (52 000) just underneath mollusca, then nematoda. Nematodes are hard to describe but hypothetically in numbers are close to arthropoda. Very successful in terms of the number of classes, were probably around at the cambrian. When looki(cid:374)g at the groups, they"re extraordinarily different morphologically very diverse. Some are terrestrial, dessert like, marine almost every environment except flight. Primarily the group is marine deep, intertidal. 50-60 000 half of mollusca are dominated by this class the gastropoda. Class cephalopod - squid, octopus (benthic), cuttlefish, nautilus. Nautilus has large simple eye, the tentacles, and a large shell (hoodie over their tentacles) represent the shelled cephalopods; very few species left. Cephalopods use to have many more species and they had shelled construction but through evolution there has been disappearance of the shell.
