BIO1011 Lecture Notes - Lecture 16: Cephalization, Symmetry In Biology, Trematoda
10 Aug 2018
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Animal phylogeny: relationships between phyla, points of agreement, all animals share a common ancestor (metazoa are monophyletic, sponges (porifera) are basal animals, all other animals (eumetazoa) have tissues, most a(cid:374)i(cid:373)al phyla (cid:271)elo(cid:374)g to the (cid:272)lade (cid:862)bilateria(cid:863, evolutionary relationships. Shared characteristics due to a common ancestry (evolutionary history) Invertebrate diversity: defined by lack of vertebrae, not monophyletic. Invertebrates include: lophotrochozoa, ecdysozoa, deuterostomia, echinodermata, chordata, urochordata, cephalochordata, craniata/vertebrata. Triploblastic development: all bilateria are, bilaterally symmetrical (2 germ layers, triploblastic (3 germ layers, ectoderm, endoderm, mesoderm. Increase size: hydrostatic skeleton, type of coelom, coelomates, pseudocoelomates, acoelomates. Phylum platyhelminthes (flatworms: bilateral symmetry, triploblastic, acoelomates, habitats, marine, freshwater, damp terrestrial, parasitic. Flatworms are acoelomates: triploblastic animals, ectoderm > epidermis, endoderm > blind gut, mesoderm fills the space between endo- and ectoderm. Flatness allows diffusion: no respiratory system, no circulatory system, no skeleton. Limited cephalisation: eyes, frontal ganglia, nerve cords. Feeding: blind gut (no anus, absorption in tapeworms.
