The Noncoelomate Animals Chapter 44 Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

General Features of Animals Classification of Animals Two subkingdoms generally recognized: Parazoa - Lack definite symmetry and posses neither tissues or organs. ex: sponges Eumetazoa - Definite shape and symmetry, and tissues organized into organs. Radiata - Diploblastic Endoderm and ectoderm Bilateria - Triplobalstic endoderm, ectoderm & mesoderm Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Key Transitions in Body Plan Evolution of Tissues First key transition in animal body plan. Evolution of Bilateral Symmetry Radial Symmetry - Regular arrangement of parts around central axis. Bilateral Symmetry - Right and left halves form mirror images. Dorsal vs. Ventral Anterior vs. Posterior Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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Key Transitions in Body Plan Evolution of a Body Cavity Presence of a body cavity allows digestive tract to be larger and longer. Storage of undigested food. More complete digestion. More space for gonads to expand. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Key Transitions in Body Plan Kinds of Body Cavities Acoelomates - No body cavity. Pseudocoelomates - Possess pseudocoelom. Coelomates - Possess coelom. Parietal peritoneum - Epithelium lining outer wall of coelom. Visceral peritoneum - Epithelium covering internal organs. Advantages of a Coelom Allows contact between mesoderm and endoderm, so that primary induction can occur during development. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Key Transitions in Body Plan Evolution of Protostome and Deuterostome Cells of embryonic Protostome each contain different portion of regulatory signals. Any cell of Deuterostome can develop into a complete organism. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Key Transitions in Body Plan Open circulatory system Blood passes from vessels into sinuses, mixes with body fluid, and then reenters vessels in another location. Closed circulatory system Blood is physically separated from other body fluids and can be separately controlled. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Key Transitions in Body Plan Evolution of Segmentation Each segment may go on to develop a more or less complete set of adult organs. Locomotion is far more effective when individual segments can move independently due to flexibility of movement. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Parazoa Sponges (Porifera) Most lack symmetry. Adults are sessile. Little coordination among cells. Three functional layers Choanocytes Mesohyl Outer epithelial layer Spicules Beating of flagella lining interior draws water in through numerous pores. Small organisms are filtered out of the water, which flows through passageways and eventually out an osculum. Reproduction done by fragmentation as well as sexually. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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Eumetazoa: The Radiata Cnidarians Nearly all marine. Carnivorous Cnidocytes Nematocysts Two basic body plans. Polyps and Medusae Fertilized eggs give rise to planulae. Internal extracellular digestion. Distinct tissues Epidermis and nervous system develop from ectoderm. Gastrodermis develops from endoderm. True body symmetry Radiata Cnidaria Ctenophora Bilateria All others Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Eumetazoa: The Radiata Classes of Cnidarians Hydrozoa - Hydroids Scyphozoa - Jellyfish Cubozoa - Box Jellyfish Anthozoa - Sea Anemones and Corals Ctenophorans (Comb Jellies) Propel through the water by means of eight comb-like plates of fused cilia. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Eumetazoa: The Bilateral Acoelomates Bilateral Symmetry Digestive tract is only internal cavity. Phylum Platyhelminthes: The Flatworms Among simplest bilaterally symmetrical animals, but have a definite head at the anterior end, and do possess organs. Flatworms Cannot feed, digest, and eliminate food simultaneously. Absorb food directly through body walls. Have excretory system. Most are hermaphroditic. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Eumetazoa: The Bilateral Acoelomates Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Eumetazoa: The Bilateral Acoelomates Class Turbellarians: Turbellarians Only one of three classes are freeliving. Class Trematoda: The Flukes Liver Fluke Clonorchis sinensis Miracidium - Eggs (passed in feces) Rediae - Elongated, nonciliated larvae. Cercariae - Tadpole-like larval stage Metacercariae - Adult stage Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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Eumetazoa: The Bilateral Acoelomates Class Cestoda: The Tapeworms Hang on to the inner walls of their hosts by means of specialized terminal attachment organs, and absorb food through their skins. Scolex - Attachment organ Neck - Unsegmented Proglottids - Repetitive segments. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Eumetazoa: The Bilateral Acoelomates Phylum Nemertea: The Ribbon Worms Simplest animals that possess a complete digestive system. Mouth and anus. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Pseudocoelomates Internal Body Cavity Pseudocoel serves as hydrostatic skeleton. Gains rigidity from being filled with fluid under pressure. Lack a defined circulatory system. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Pseudocoelomates Phylum Nematoda: The Roundworms Bilaterally symmetrical unsegmented worms Covered by flexible, thick cuticle. Mouth equipped with stylets. Food passes through mouth as result of sucking action of pharynx. Lack flagella or cilia. Reproduction is sexual. Trichinella regularly parasitize humans. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Pseudocoelomates Phylum Rotifera: Rotifers Small, bilaterally symmetrical, basically aquatic animals with a crown of thick cilia at their heads. Well developed food processing apparatus. “Wheel Animals” Phylum Cycliophora Relatively New Circular mouth surrounded by fine, hairlike cilia. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Reevaluating Animal Body Plan Evolution Biologists have traditionally inferred the general relationships among animal phyla by examining what appeared to be fundamental characters. These key morphological characters are not as conservative as previously believed. Molecular Phylogenies Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies