What Is an Invertebrate? Invertebrates are animals that have no backbone, or vertebral column. Invertebrates make up over 95% of all animal species. They include sea stars, worms, jellyfishes, and insects. Copyright Pearson Prentice Hall

26-2 Sponges Photo Credit: Fred McConnaughey/Photo Researchers, Inc. Copyright Pearson Prentice Hall

What is a Sponge? What is a Sponge? Sponges are the simplest and most ancient animals in the phylum Porifera which means “pore-bearers.” live their entire adult life as sessile organisms; attached to a single spot. Copyright Pearson Prentice Hall

Form and Function in Sponges Body Plan Sponges are asymmetrical; they have no front or back ends, no left or right sides. Sponges carry out basic functions, such as feeding and circulation, by moving water through their bodies. Copyright Pearson Prentice Hall

Form and Function in Sponges Feeding Sponges are filter feeders. As water moves through the sponge, food particles are trapped and engulfed by choanocytes that line the body cavity. Copyright Pearson Prentice Hall

Form and Function in Sponges Circulation Sponges rely on movement of water through their bodies to carry out body functions. Copyright Pearson Prentice Hall

Branching Tube Sponge

Stove Pipe Sponge

Vase Sponges

Barrel Sponges

Ball Sponges

Rope Sponges

26-3 Cnidarians Copyright Pearson Prentice Hall

What is a Cnidarian? What is a Cnidarian? Cnidarians are soft-bodied, carnivorous animals that have stinging tentacles arranged in circles around their mouths. Copyright Pearson Prentice Hall

Form and Function in Cnidarians Body symmetry Cnidarians are radially symmetrical. They have a central mouth surrounded by numerous tentacles that extend outward from the body. Copyright Pearson Prentice Hall

Form and Function in Cnidarians Feeding A cnidarian pulls its food through its mouth and into its gastrovascular cavity, a digestive chamber with one opening. Food enters and wastes leave the body through that same opening. Copyright Pearson Prentice Hall

Form and Function in Cnidarians Circulation Following digestion, nutrients are usually transported throughout the body by diffusion. Copyright Pearson Prentice Hall

Portuguese man-of-war Colonial Hydrozoan (not a single organism Tentacles sting prey such as fish & humans Polyps in colony feed Has gas-filled air float copyright cmassengale

Anthozoans copyright cmassengale

Hydra Feeding copyright cmassengale 25

Food in Gastrovascular Cavity copyright cmassengale

Scyphozoans copyright cmassengale

Some Jellyfish Show Luminescence 28 28

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27–1 Flatworms Photo Credit: ©Carolina Biological Supply Company/Phototake Copyright Pearson Prentice Hall

What Is a Flatworm? Flatworms are acoelomates, which means they have no coelom. A coelom is a fluid-filled body cavity that is lined with tissue derived from mesoderm. The digestive cavity is the only body cavity in a flatworm. Flatworms have bilateral symmetry. Flatworms are the simplest animals to have 3 embryonic germ layers Copyright Pearson Prentice Hall

Form and Function in Flatworms Feeding  Flatworms have a digestive cavity with a single opening through which both food and wastes pass. Near the mouth is a muscular tube called a pharynx. Flatworms extend the pharynx out of the mouth. The pharynx then pumps food into the digestive cavity. Copyright Pearson Prentice Hall

Form and Function in Flatworms Circulation  Flatworms do not need a circulatory system to transport materials they rely on diffusion Copyright Pearson Prentice Hall

Tapeworm Anatomy

Copyright Pearson Prentice Hall

27–2 Roundworms Copyright Pearson Prentice Hall

Roundworms Roundworms

What Is a Roundworm? Roundworms are unsegmented worms that have pseudocoeloms and digestive systems with two openings—a mouth and an anus. Roundworms have bilateral symmetry. Copyright Pearson Prentice Hall

Form and Function in Roundworms Feeding Many free-living roundworms use grasping mouthparts and spines to catch and eat other small animals. There are a variety of parasitic roundworms as well Copyright Pearson Prentice Hall

Form and Function in Roundworms Circulation They depend on diffusion to carry nutrients and waste through their bodies. Copyright Pearson Prentice Hall

Cysts in Contaminated Pork

27-3 Annelids Copyright Pearson Prentice Hall

What Is an Annelid? What Is an Annelid? Annelids are worms with segmented bodies. They have a true coelom that is lined with tissue derived from mesoderm. Annelids have bilateral symmetry. Copyright Pearson Prentice Hall

Form and Function in Annelids Feeding and Digestion In carnivorous species, the pharynx usually holds two or more sharp jaws that are used to attack prey. Annelids that feed on decaying vegetation have a pharynx covered with sticky mucus. Other annelids obtain nutrients by filter feeding. Copyright Pearson Prentice Hall

Form and Function in Annelids Circulation  Annelids typically have a closed circulatory system, in which blood is contained within a network of blood vessels. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall