Mollusks and Annelids Chapter 45 Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Body cavity lined with mesoderm cells Coelomates Coelomate Body cavity lined with mesoderm cells Allows the development of complex tissues and organs. Allows wider array of body architectures and increased body size. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Characterized by a coelom. Great economic significance Pearls Coelomates Mollusks (Mollusca) Extremely diverse. Characterized by a coelom. Great economic significance Pearls Mother of Pearl Economic / Environmental Costs Zebra Mussel Invasion Intermediate hosts for parasites. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Body Plan of the Mollusks Distinct bilateral symmetry. Digestive, excretory, and reproductive organs all concentrated in a visceral mass and a muscular foot. May have differentiated head. Folds constituting a mantle. Gills - Increased surface area for gas exchange. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Body Plan of the Mollusks Shells serve primarily for protection. Radula - Rasping tongue-like organ used for feeding. Circulatory system (except cephalopods) consists of a heart and an open circulatory system. Nitrogenous wasted removed by nephridia. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Body Plan of the Mollusks Reproduction in Mollusks Most have distinct male and female individuals. Most engage in external fertilization. Many have free-swimming larvae (trochophores) which closely resemble larval stage of many marine annelids. Veliger stage follows trochophore stage. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Polyplacophora: The Chitons Classes of Mollusks Polyplacophora: The Chitons Oval bodies with eight overlapping calcareous plates. Gastropoda: Snails and Slugs Heads of most have pair of tentacles with eyes at the ends. Undergo torsion during embryological development. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Bivalvia: The Bivalves Clams, scallops, mussels and oysters. Classes of Mollusks Bivalvia: The Bivalves Clams, scallops, mussels and oysters. Have two lateral shells hinged together dorsally. Mantle secretes shell and ligaments. Most are sessile filter-feeders. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cephalopoda: Octopuses, Squids, Nautilus Classes of Mollusks Cephalopoda: Octopuses, Squids, Nautilus Most intelligent of the invertebrates. Active marine predators. Foot evolved into a series of tentacles equipped with structures to capture prey. Highly developed nervous systems. Closed circulatory system Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Building of body from series of similar segments. Segmented Animals Building of body from series of similar segments. Small change in existing segment can produce new kind of segment with different function. Phylum Annelida Three characteristics: Repeated Segments Specialized Segments Connections Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Segmented Animals Body Plan of the Annelid Tube within a tube. Internal digestive tract within the coelom. Specialized for different functions. Hydrostatic skeleton for locomotion. Each segment typically possesses setae, that help anchor during locomotion. Most have closed circulatory system. Nephridia collect and transport wastes. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Classes of Annelids Polychaeta: The Polychaetes Well developed head with specialized sense organs. Parapodia on most segments. Usually lack permanent gonads. Oligochaeta: The Earthworms Hermaphroditic Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Hirudinea: The Leeches Occur mostly in fresh water. Hermaphroditic Classes of Annelids Hirudinea: The Leeches Occur mostly in fresh water. Hermaphroditic Develop clitellum during breeding season. Unable to self-fertilize. Secrete anticoagulant into wounds. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Polychaeta: The Polychaetes Classes of Annelids Polychaeta: The Polychaetes Well developed head with specialized sense organs. Parapodia on most segments. Usually lack permanent gonads. Oligochaeta: The Earthworms Hermaphroditic Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Lophophorates Phylum Phoronida: The Phoronids Lophophore - Circular or U-shaped ridge around the mouth bearing one or two rows of ciliated, hollow tentacles. Functions as surface for gas exchange and as food-collection organs. Use cilia to capture food. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Phylum Ectoprocta: The Bryozoans Lophophorates Phylum Ectoprocta: The Bryozoans Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Phylum Brachiopoda: The Brachiopods Lophophorates Phylum Brachiopoda: The Brachiopods 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