Section 1 Echinoderms Chapter 38 Objectives • Discussfour distinguishing characteristics of echinoderms. • Describerepresentative species from each of the five classes of echinoderms. • Describethe water-vascular system and other major body systems of echinoderms. • Comparesexual and asexual reproduction in sea stars.

Section 1 Echinoderms Chapter 38 Characteristics • Echinoderms are radially symmetricaldeuterostomes. • Most living species of echinoderms are motile, but some are sessile. • Most echinoderms have: • pentaradial symmetry • an endoskeleton made up of ossicles • a water-vascular system • tube feet

Section 1 Echinoderms Chapter 38 Classification • There are about 7,000 species of echinoderms. • There are five major classes of echinoderms: • Crinoidea • Ophiuroidea • Echinoidea • Holothuroidea • Asteroidea

Section 1 Echinoderms Chapter 38 Classification, continued Class Crinoidea • Members of the class Crinoidea, called crinoids, include the sea lilies and feather stars. • In both types of crinoids, five arms extend from the body and branch to form many more arms—up to 200 in some feather star species.

Section 1 Echinoderms Chapter 38 Classification, continued Class Ophiuroidea • The 2,000 species of basket stars and brittle stars make up the largest echinoderm class, Ophiuroidea, which means “snake-tail.” • Members of this class are distinguished by their long, narrow arms, which allow them to move more quickly than other echinoderms.

Section 1 Echinoderms Chapter 38 Classification, continued Class Echinoidea • The class Echinoidea consists of about 900 species of sea urchins and sand dollars. • Echinoidea means “spinelike.” • The internal organs are enclosed within a fused, rigid endoskeleton called a test.

Section 1 Echinoderms Chapter 38 Classification, continued Class Holothuroidea • Sea cucumbers belong to the class Holothuroidea. • Holothuroidea means “water polyp.” • Most of these armless echinoderms live on the sea bottom, where they crawl or burrow into soft sediment by using their tube feet.

Section 1 Echinoderms Chapter 38 Classification, continued Class Asteroidea • The sea stars, or starfish, belong to the class Asteroidea, which means “starlike.” • Sea stars are economically important because they prey on oysters, clams, and other organisms that humans use as food.

Section 1 Echinoderms Chapter 38 Structure and Function of Echinoderms External Structure • The body of a sea star is composed of several arms that extend from a central region. Two rows of tube feet run along the underside of each arm. • The side of the body where the mouth is located is referred to as the oral surface. The opposite side is called the aboral surface. • The body of a sea star is usually covered with short spines. Surrounding each spine in many sea stars are numerous tiny pincers called pedicellariae.

Section 1 Echinoderms Chapter 38 Structure and Function of Echinoderms, continued Water-Vascular System • The water-vascular system is a network of water-filled canals that are connected to the tube feet. • This coordinated system enables sea stars to climb slippery rocks and capture prey. • Water enters through the madreporite, passes down the stone canal to the ring canal, then through the radial canal to the end of each arm and to the tube feet. • The upper end of each tube foot is a bulblike sac called an ampulla.

Section 1 Echinoderms Chapter 38 Structure and Function of Echinoderms, continued Feeding and Digestion • The sea star can turn its cardiac stomach inside out through its mouth when it feeds. • The cardiac stomach transfers food to the pyloric stomach, which connects to a pair of digestive glands in each arm. • Most sea stars are carnivorous.

Section 1 Echinoderms Chapter 38 Structure and Function of Echinoderms, continued Other Body Systems • Like other echinoderms, the sea star has no circulatory, excretory, or respiratory organ systems. • The nervous system consists mainly of a nerve ring and a radial nerve that runs along each arm.

Section 1 Echinoderms Chapter 38 Structure and Function of Echinoderms, continued Reproduction and Development • Most echinoderms have separate sexes. • Each arm of the sea star contains a pair of ovaries or testes. • Fertilization occurs externally in water. • Each fertilized egg develops into a bilaterally symmetrical, free-swimming larva called a bipinnaria. • Echinoderms have remarkable powers of regeneration.

Section 1 Echinoderms Chapter 38 Anatomy of a Sea Star

Section 1 Echinoderms Chapter 38 Characteristics of Echinoderms Click below to watch the Visual Concept. Visual Concept

Section 1 Echinoderms Chapter 38 Water Vascular System Click below to watch the Visual Concept. Visual Concept

Section 1 Echinoderms Chapter 38 Anatomy of a Sea Star Click below to watch the Visual Concept. Visual Concept

Section 1 Echinoderms Chapter 38 Types of Echinoderms Click below to watch the Visual Concept. Visual Concept

Section 2 Invertebrate Chordates Chapter 38 Objectives • Listthe major characteristics of chordates. • Describethe evolution and classification of invertebrate chordates. • Describethe structure of lancelets. • Describethe structure of tunicates.

Section 2 Invertebrate Chordates Chapter 38 Characteristics • Chordates, phylum Chordata, are characterized by having a notochord. • In most vertebrates, the notochord is present in embryos but reduced in adults. • In addition, all chordates have the following characteristics during some stage of their life: • a dorsal nerve cord • pharyngeal pouches • a postanal tail

Section 2 Invertebrate Chordates Chapter 38 Evolution and Classification • Echinoderms and chordates likely evolved from a common ancestor. • The phylum Chordata is divided into three subphyla: • Vertebrata • Cephalochordat • Urochordata

Section 2 Invertebrate Chordates Chapter 38 Evolution and Classification, continued Subphylum Cephalochordata • The subphylum Cephalochordata contains about two dozen species of lancelets. • Lancelets retain their notochord, dorsal nerve cord, pharyngeal pouches, and postanal tail throughout their life. • Lancelets feed by filtering water through the slits in the pharynx. The water leaves the body through the atriopore.

Section 2 Invertebrate Chordates Chapter 38 Evolution and Classification, continued Subphylum Urochordata • The subphylum Urochordata contains about 2,000 species commonly called tunicates or sea squirts. • As adults, most tunicates are sessile, barrel-shaped filter feeders that live on the sea bottom. They may be solitary or colonial. • Tunicates are hermaphrodites.

Section 2 Invertebrate Chordates Chapter 38 Lancelet Interior

Section 2 Invertebrate Chordates Chapter 38 Exploration of a Lancelet

Section 2 Invertebrate Chordates Chapter 38 Adult Tunicate

Section 2 Invertebrate Chordates Chapter 38 Characteristics of Invertebrate Chordates Click below to watch the Visual Concept. Visual Concept

Section 2 Invertebrate Chordates Chapter 38 Parts of a Chordate Click below to watch the Visual Concept. Visual Concept

Section 2 Invertebrate Chordates Chapter 38 Anatomy of a Lancelet Click below to watch the Visual Concept. Visual Concept

Section 2 Invertebrate Chordates Chapter 38 Anatomy of a Tunicate Click below to watch the Visual Concept. Visual Concept

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