BIO153H5 Lecture Notes - Lecture 17: Notochord, Haikouella, Vertebrate
Document Summary
Heaviest on land: argentinosaurs sp. , up to 100 tonnes. Biggest ever: blue whale (balaenoptera muscles)l up to 180 tonnes, 30 m. Notochord (stabilizing structure made out of a somewhat rigid and flexible compound) In tunicates, the chordate ch aracteristics are only visible i n the larval form. A head is defi(cid:374)ed (cid:271)y the prese(cid:374)(cid:272)e of : a skull, sensory organs, a brain, all of the above. Can define the front end (where the head is) and the back end of an organism. We (cid:272)a(cid:374) ha(cid:448)e heads o(cid:374)ly i(cid:374) a(cid:374)i(cid:373)als (cid:449)ith (cid:271)ilateral sy(cid:373)(cid:373)etry (you (cid:272)a(cid:374)"t ha(cid:448)e a head i(cid:374) a radially sy(cid:373)(cid:373)etri(cid:272)al organism, since a head by definition is a concentration of cells in a certain area) Radially symmetry organisms need sensory organs distributed all over its body. If you have a head, you can concentrate sensory organs to one area (the head)< allowing you to have more diverse sensory organs and more sensitive ones as well.
