BIOL 2P92 Lecture 1: February 16, 2017
Document Summary
Unsegmented, although internal structures (ganglia, mucous glands) are serially repeated. Has proboscis (pushed out under hydrostatic pressure. Has ciliated groove where food particles run down the groove, and itno the mouth to be digested. Extreme metamerism: seg(cid:373)e(cid:374)tatio(cid:374) outside does(cid:374)"t (cid:373)irror seg(cid:373)e(cid:374)tatio(cid:374) o(cid:374) the i(cid:374)side, has serial repetition inside. Blood vessels (front) are enlarged pumps (hearts: complicated blood vessel system, closed circulatory system carries nutrients and waste products. Hydrostatic skeleton formed by liquid pressure in segments in between the septa. Crop pre-stomach: where it holds food prior to digestion. Gizzard front of the digestive system: muscular, where foodstuff is crushed (mechanical digestion) Presence of intestine where majority of breakdown occurs. No eyes, but have tactile and chemosensitive organs, some of which are called prostomium (in front of the mouth; stomia = mouth) Main nerves are ventral (invertebrates have ventral nerve cords; vertebrates have dorsal nerve cords: has projections (each muscle has its own nerves)