BIOL 1108 Lecture Notes - Lecture 14: Animal, Eukaryote, Synapomorphy
29 Oct 2018
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Document Summary
Phylogeny charts the evolutionary relationships among more than a million animal species. The earliest branches of the animal tree include sponges, cnidarians, ctenophores, and placozoans. Bilaterians, including protostomes and deuterostomes, have bilateral symmetry and develop from three germ layers. Most vertebrates have a bony cranium and vertebral column; vertebrates include fish, amphibians, reptiles, birds, and mammals. Animals first evolved more than 600 million years ago in the oceans, and by 500 million years ago the major structural and functional body plans of animal phyla were in place. We need to review our approach to classification. Fungi, plantae, and animalia separately evolved from single-celled eukaryotes. Eukarya is a monophyletic taxon with multiple synapomorphies of cell structure. Eukarya includes both single- and multi-celled organisms. Remember that within the eukarya, there are multiple major groups with unclear relationships. The choanoflagellates resemble a cell type in basal animals, reflecting a sister taxon relationship.
