BIOL 2P92 Lecture 1: February 15, 2017
22 Mar 2017
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Document Summary
Has hydrostatic skeleton and metamerism (segmentation: repetition due to underlying repeating genes. Has a nervous system, circulatory system, digestive system running head to toe, strong muscles. Polychaetes: multiple setae, paraphyletic: lots of hair (bristle-like) Hirudinidae: (monophyletic) leeches: hirudo: type of leech (most common) Biramous parapodia: has 2 parts, ancestral trait that lead to the evolution of tetrapods (changed) I. e. scale worms: commensals: lives on other invertebrates but causes no harm to its host, has bilateral symmetry. Big enough to have internal vessels and capacity to have something similar to a skeleton that is hydrostatic. Internal dividers (septa) in polychaetes and oligochaetes between each segment: contains its own liquid, major septal muscles: longitudinal (inner; shortens segment that brings liquid back in) and circular muscles (outside; lengthens segment and brings liquid out) Epitoke: reproductive form: buds off and creates a new worm. Tube-dwelling sedentaria: filter-feeders, has a sac in burrow.
