AEBI 211 Lecture Notes - Lecture 9: Hydrostatic Skeleton, Symmetry In Biology, Flatworm
Document Summary
Phylum | platyhelminthes: commonly called flatworms, ancestral species were free-living in ancient oceans, became preys to more complex animals, now parasitic: flukes, tapeworms, some still free-living: planaria, triploblastic, acoelomate, bilateral symmetry, cephalization, tissue-organ level of biological complexity. Incomplete/blind gut: tissues organized into organs but not system, no respiratory, circulatory, skeletal systems, hydrostatic skeleton, respiration through diffusion. Class turbellaria | planaria : 5mm-50cm, mostly free-living, some symbiotic, blind gut -- waste ejected through mouth, reproduction, sexual mostly monoecious, asexual transverse fission = split in 2 + regenerate missing parts. Intermediate host is mollusc: animal ambassador swimmer"s itch caused by trematode shistosoma, normally passes b/w snails and ducks, cercariae form can enter human skin but dead-end for flukes. C. elegans: free-living nematode, used as model organism, 1st multicellular animal to have whole genome sequenced, only organisms to have all its neuronal wiring mapped.