Lecture 11 - Hypothesized phylogeny of animals based on...

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1 Animals Figure 32.11 Calcarea Silicarea Ctenophora Cnidaria Echinodermata Chordata Brachiopoda Phoronida Ectoprocta Platyhelminthes Nemertea Mollusca Annelida Rotifera Nematoda Arthropoda “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Two tissue layers, radial symmetry Three tissue layers, Bilateral symmetry Hypothesized phylogeny of animals based on molecular data Outline (phyla in red) • Bilateria: – Lophotrochozoans • Platyhelminthes - the flatworms • Lophophorates : Brachiopods , (Phoronids and Ectoprocts) • Trochozoans : Molluscs and Annelids – Ecdysozoa : Nematodes , Arthropods – Deuterostomes : Echinoderms , Chordates Calcarea Silicarea Ctenophora Cnidaria Echinodermata Chordata Brachiopoda Phoronida Ectoprocta Platyhelminthes Nemertea Mollusca Annelida Rotifera Nematoda Arthropoda “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate • Bilateria – All have bilateral symmetry and triploblastic development Flatworms Members of phylum Platyhelminthes Live in marine, freshwater, and damp terrestrial habitats Are flattened and have a gastrovascular cavity Although placed with the lophotrochozoans They lack either a lophophore or a trochophore larvae Although flatworms undergo triploblastic development they are acoelomates Calcarea Silicarea Ctenophora Cnidaria Echinodermata Chordata Brachiopoda Phoronida Ectoprocta Platyhelminthes Nemertea Mollusca Annelida Rotifera Nematoda Arthropoda “Radiata” “Porifera” DeuterostomiaLophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Flatworms are acoelomates Figure 32.8c Body covering (from ectoderm) Tissue- filled region (from mesoderm) Digestive tract (from endoderm) Acoelomate. Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall. (c)
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2 Flatworms are divided into four classes Table 33.2 Turbellarian • Turbellarians – Are nearly all free-living and mostly marine The best-known turbellarians, commonly called planarians – Have light-sensitive eyespots and centralized nerve nets Pharynx. The mouth is at the tip of a muscular pharynx that extends from the animal’s ventral side. Digestive juices are spilled onto prey, and the pharynx sucks small pieces of food into the gastrovascular cavity, where digestion continues. Digestion is completed within the cells lining the gastro- vascular cavity, which has three branches, each with fine subbranches that pro- vide an extensive surface area. Undigested wastes are egested through the mouth. Ganglia. Located at the anterior end of the worm, near the main sources of sensory input, is a pair of ganglia, dense clusters of nerve cells.
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