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

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

Eumetazoa: The Radiata Distinct tissues  Epidermis and nervous system develop from ectoderm.  Gastrodermis develops from endoderm. True body symmetry  Radiata - Cnidaria - Ctenophora  Bilateria - All others Cnidarians  Nearly all marine.  Carnivorous - Cnidocytes  Nematocysts  Two basic body plans. - Polyps and Medusae  Fertilized eggs give rise to planulae.  Internal extracellular digestion.

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

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

Copyright © McGraw-Hill Companies Permission required for reproduction or display