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Chapter 38 Table of Contents Section 1 Echinoderms Echinoderms and Invertebrate Chordates Chapter 38 Table of Contents Section 1 Echinoderms Section 2 Invertebrate Chordates

Section 1 Echinoderms Chapter 38 Objectives Discuss four distinguishing characteristics of echinoderms. Describe representative species from each of the five classes of echinoderms. Describe the water-vascular system and other major body systems of echinoderms. Compare sexual and asexual reproduction in sea stars.

Chapter 38 Characteristics Section 1 Echinoderms Chapter 38 Characteristics Echinoderms are radially symmetrical deuterostomes. 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

Chapter 38 Classification 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

Classification, continued 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.

Classification, continued 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.

Classification, continued 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.

Classification, continued 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.

Classification, continued 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.

Structure and Function of Echinoderms 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.

Structure and Function of Echinoderms, continued 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.

Structure and Function of Echinoderms, continued 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.

Structure and Function of Echinoderms, continued 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.

Structure and Function of Echinoderms, continued 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

Characteristics of Echinoderms Section 1 Echinoderms Chapter 38 Characteristics of Echinoderms

Section 1 Echinoderms Chapter 38 Pentaradial Symmetry

Section 1 Echinoderms Chapter 38 Water Vascular System

Section 1 Echinoderms Chapter 38 Anatomy of a Sea Star

Section 1 Echinoderms Chapter 38 Types of Echinoderms

Chapter 38 Objectives List the major characteristics of chordates. Section 2 Invertebrate Chordates Chapter 38 Objectives List the major characteristics of chordates. Describe the evolution and classification of invertebrate chordates. Describe the structure of lancelets. Describe the structure of tunicates.

Chapter 38 Characteristics 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

Evolution and Classification 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 Cephalochordata Urochordata

Evolution and Classification, continued 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.

Evolution and Classification, continued 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

Exploration of a Lancelet Section 2 Invertebrate Chordates Chapter 38 Exploration of a Lancelet

Section 2 Invertebrate Chordates Chapter 38 Adult Tunicate

Characteristics of Invertebrate Chordates Section 2 Invertebrate Chordates Chapter 38 Characteristics of Invertebrate Chordates

Section 2 Invertebrate Chordates Chapter 38 Parts of a Chordate

Section 2 Invertebrate Chordates Chapter 38 Anatomy of a Lancelet

Section 2 Invertebrate Chordates Chapter 38 Anatomy of a Tunicate

Chapter 38 Multiple Choice Standardized Test Prep Multiple Choice 1. In a sea star, gas exchange and excretion of wastes take place by diffusion through which of the following structures? A. pharynx B. skin gills C. atriopore D. radial canals

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 1. In a sea star, gas exchange and excretion of wastes take place by diffusion through which of the following structures? A. pharynx B. skin gills C. atriopore D. radial canals

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 2. Which of the following types of symmetry is characteristic of echinoderms? F. biradial G. bilateral H. pentaradial J. pentalateral

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 2. Which of the following types of symmetry is characteristic of echinoderms? F. biradial G. bilateral H. pentaradial J. pentalateral

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 3. Which of the following classes of echinoderms most closely resembles the fossils of ancient echinoderms? A. Crinoidea B. Asteroidea C. Echinoidea D. Holothuroidea

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 3. Which of the following classes of echinoderms most closely resembles the fossils of ancient echinoderms? A. Crinoidea B. Asteroidea C. Echinoidea D. Holothuroidea

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 4. Which of the following is found in adult tunicates, or sea squirts? F. eyespot G. notochord H. spinal cord J. pharynx with slits

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 4. Which of the following is found in adult tunicates, or sea squirts? F. eyespot G. notochord H. spinal cord J. pharynx with slits

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued The illustration below shows a sea star and a sand dollar. Use the illustration to answer the question that follows.

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 5. To which phylum do these animals belong? A. Chordata B. Vertebrata C. Arthropoda D. Echinodermata

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 5. To which phylum do these animals belong? A. Chordata B. Vertebrata C. Arthropoda D. Echinodermata

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 6. Cardiac stomach : digestion :: atriopore : F. excretion G. respiration H. circulation J. reproduction

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 6. Cardiac stomach : digestion :: atriopore : F. excretion G. respiration H. circulation J. reproduction

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued The diagram below shows a lancelet. Use the diagram to answer the question that follows.

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 7. Which four structures are the main distinguishing characteristics of chordates? A. 1, 2, 3, 4 B. 1, 2, 3, 8 C. 2, 3, 4, 6 D. 2, 3, 4, 9

Multiple Choice, continued Chapter 38 Standardized Test Prep Multiple Choice, continued 7. Which four structures are the main distinguishing characteristics of chordates? A. 1, 2, 3, 4 B. 1, 2, 3, 8 C. 2, 3, 4, 6 D. 2, 3, 4, 9

Chapter 38 Short Response Standardized Test Prep Short Response Echinoderms and chordates are believed to have evolved from a common ancestor. Describe the evidence that supports this view.

Short Response, continued Chapter 38 Standardized Test Prep Short Response, continued Echinoderms and chordates are believed to have evolved from a common ancestor. Describe the evidence that supports this view. Answer: Because both echinoderms and chordates are deuterostomes and all other invertebrates are protostomes it is believed that they descended from the same ancestor.

Chapter 38 Extended Response Standardized Test Prep Extended Response The fossil record of echinoderms dates to the Cambrian period, more than 500 million years ago. Scientists have observed many well-preserved echinoderm species from this period. Part A Based on the fossil evidence, which characteristics did the earliest adult echinoderms have, in terms of symmetry and ability to move? Part B Based on your answer to Part A, describe the evolution of echinoderms.

Extended Response, continued Chapter 38 Standardized Test Prep Extended Response, continued Answers Part A They were bilaterally symmetrical and sessile. Part B Present-day echinoderms are radially symmetrical and may move about. Echinoderms probably evolved radial symmetry as an adaptation to their sessile existence. Later, they evolved mobility. Over time, mobile species became more numerous , and today most species can move about. It is unlikely that echinoderms evolved mobility and then radial symmetry, because there would be no selective pressure for radial symmetry in a species that was mobile.