BIO SCI 94 Lecture Notes - Lecture 17: Choanoflagellate, Detritivore, Synapomorphy
15 Feb 2019
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Document Summary
Cambrian explosion-radiation of animals, 550 millions years ago. Move under own power at one point. Neurons- nerve cells, transmit electrical signals to other cells. Muscle cells- change shape of body by contracting. Animals only multicellular heterotrophs that ingest food before digesting it. Neurons connect to one another form nervous system. Fossil record inconsistent, only direct evidence of: Provides information on relative similarity of genes of diverse organisms. Provides insight to phylogenetic relationship and evolutionary history. Sponges include two most basal animal lineages. Choanocytes- sponge feeding cells- trap/ingest food particles. Choanoflagellates sometime for colonies-group of attached individuals. Sponges once part of colonies of single celled protists. Epithelium-layer of tightly joined cells, covers interior/exterior surface of anima. Spicules-stiff spikes of silica/calcium carbonate, provide structural support to ecm. No unanimous agreement sponges are monophyletic group. Support hypothesis sponges most basal animal group. Support sponges have complex developmental tool kit of genes despite morphical simplicity.
