01:119:116 Lecture Notes - Lecture 6: Sequential Hermaphroditism, Phylogenetic Tree, Mesohyl
16 Oct 2018
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Basal animals at root of phylogenetic tree. Reproduce sexually; most are hermaphrodites: each individual acts as male and female, sequential hermaphroditism. Eumetazoans is clade of (cid:498)true animals(cid:499) (cid:523)have true tissues(cid:524) 2/7/14: predators, use tentacle to catch prey, tentacles have cnidocytes, cells used in defense and to capture prey, contain cnidia (capsule-like organelle that explodes outward, nematocysts are specialized cnidia with stinging threat to penetrate prey. All members have bilateral symmetry and are triploblastic. Most have digestive tract with separate mouth and anus. Molecular evidence suggests 3 major clades (lophotrochozoa, ecdyzoa, Deuterostomia: lophotrochozoa, some species have a lophophore, some species have trochophore larvae, some have neither of these, 18 different phyla (but discuss only 6, phylum platyhelminthes, dorso-ventrally flattened, acoelomates, most free living (ex. Planaria: fig 32. 10: some parasitic (ex. 33. 11, 33. 12: phylum rotifera, pseudocoelomates (fluid filled cavity that serves as hydrostatic skeleton, very small (50 micrometers to. 2/7/14: in marine, freshwater, and damp soils, earthworms are example ( 33. 25)
