ZOL 353 Lecture Notes - Lecture 32: Bilateria, Aposematism, Anatomical Terms Of Motion
Document Summary
This is cleavage: from the 4-cell to 8-cell stage it is phylogenetically informative. In the superphylum deuterostomes, cleavage is radial, so cells 4-8 are symmetrically lined up with cells 1-4: deuterostome phyla are echinodermata, hemichordata, and chordata. If the superphylum protostomes cleavage is spiral so cells 508 are not lined up with cells 1-4: protostome phyla are all other bilaterian groups. Edia(cid:272)ara(cid:374) (cid:894)ve(cid:374)dia(cid:374)(cid:895) (cid:862)a(cid:374)i(cid:373)als(cid:863: 635-540 ma, these are the oldest complex, multicellular organisms known, soft-bodied, highly varied, trace fossils (impressions, unusual preservation conditions, related to presence of microbial mats, flourished worldwide in aquatic environments. Sponges: phylum porifera: the only non-metazoan animal group, the simplest animals, no organs. No gut: no nervous system, no circulatory system. No excretory system: tissue layers poorly differentiated. In sexual reproduction, fog of sperm usually released that fertilizes eggs held within: many are toxic, distasteful, or caustic.
