BIS 2C Lecture Notes - Lecture 25: Hexactinellid, Choanocyte, Spongin
18 Dec 2016
School
Department
Course
Professor
Document Summary
Answer: unique cell to cell junctions: unique junctions between cells (facilitates cell2cell. Very few synapomorphies in animals (lots of unique features, but not necessarily synapomorphies) Despite much intuitive sense that animals are monophyletic, there are only a few characters that are unambiguous synapomorphies: communication) Good quiz question: provide evidence that supports the unique evolution of multicellularity in animals. Tunicates are most closely related to chordates. Phylum porifera: calcarea 3) hexactinellida do intracellular digestion (spongeee) Synapomorphies for phylum porifera: choanocytes = a synapomorphy for porifera. Only a few types of cells (~15) Totipotency = sponge cells can change into other cells. Sponges are monophyletic (used to be paraphyletic) 8000 species divided into 3 clades: 1) demospongiae (most diverse) Mostly filter feeders and since they are monoblastic aka no gut, they only. Demosponges have spicules made mostly of spongin. Structure and chemistry are different between sponge clades (ex: spicules = serve as supportive and defensive structures calcium carbonate, silicon dioxide aka glass)
