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Home , Brittle star, Chordate, Deuterostome, Echinoderm, List of animal classes, Ossicle (echinoderm)

Section 1 Section 1 FocusFocus Overview Objectives Development Before beginning this section ● Compare the developmental If you have been to a saltwater , you’re sure to have seen review with your students the found in echinoderms, which are spiny that live on the with that found in deuteros- bottom. How could echinoderms like the shown on the objectives listed in the Student tomes. 8B Edition. This lesson describes the first page of this chapter be related to such as , ● Describe the major charac- which are primarily ? The answer lies in their early devel- similarities and differences between teristics of echinoderms. 8C opment. As an develops, it goes through a gastrula stage. As and ● TAKS 2 shown in Figure 1, a gastrula has an opening to the outside called development and introduces stu- Summarize how the star’s the blastopore. In acoelomate animals, the develops from or dents to the groups of organisms functions. 7B TAKS 3 near the blastopore. This pattern of development also occurs in that show each of these develop- some coelomate animals, such as , mollusks, and arthro- mental . Students will study Key Terms pods. Animals with that develop from or near the blastopore structure and function blastopore are called protostomes. and review examples of several dif- protostome Some animals follow a different pattern of development. In phy- ferent groups of echinoderms. deuterostome lums Echinodermata and Chordata, the —not the mouth— develops from or near the blastopore. (The mouth forms later, on water-vascular system another part of the embryo.) Animals with this pattern of develop- Bellringer skin ment are called , also shown in Figure 1. If you know Ask students to list the names of as the origin of these two terms, it’s easy to remember the differences many non- marine organisms as between the two developmental patterns. The term protostome is they can think of. (Most will be either from the Greek protos, meaning “first,” and stoma, meaning mollusks or echinoderms.) “mouth.” The prefix deutero- is from the Greek deuteros, meaning “second.” In deuterostomes, the anus develops first and the mouth develops second. MotivateMotivate Figure 1 The development of an animal embryo follows one of two patterns. ENERAL Demonstration G Gastrula Gastrula Bring in several preserved or dried specimens of echinoderms such as sea , sea stars, and sand Gut EmbryoGut Embryo dollars. You can supplement these Anus Mouth specimens with pictures in books. Allow students to inspect them and come up with as many common Blastopore Blastopore characteristics as they can. List those Coelom characteristics on the board or overhead, and refer to the list as Blastopore Blastopore you teach the specific characteristics. becomes mouth becomes anus LS Visual TAKS 2 Bio 8C Protostomes Deuterostomes

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Chapter Resource File Transparencies TT Bellringer • Lesson Plan GENERAL pp. 692–693 • Directed Reading TT Patterns of Embryonic Development TT of Chordates and Student Edition •Active Reading GENERAL TAKS Obj 2 Bio 8C Echinoderms •Data Sheet for Data Lab GENERAL TAKS Obj 3 Bio 7A TAKS Obj 3 Bio 7B TEKS Bio 7A, 7B, 8B, 8C Planner CD-ROM Teacher Edition TAKS Obj 2 Bio 8C • Reading Organizers TAKS Obj 3 Bio 7A TAKS Obj 3 Bio 7B • Reading Strategies TEKS Bio 5C, 7A, 7B, 8C TEKS Bio/IPC 3C

692 Chapter 31 • Echinoderms and Chordates Sea Sea Brittle Sea Sea TTeacheach Vertebrates stars lilies stars urchins cucumbers Class SKILL BUILDER Cephalochordata Crinoidea Echinoidea Subphylum Subphylum Class Class Class Interpreting Visuals Have students Vertebrata Urochordata Asteroidea Ophiuroidea Holothuroidea examine Figure 2. Ask them to iden- tify the first group of echinoderms that evolved (sea cucumbers) and the most recently evolved group(s) of echinoderms. (sea stars, sea lilies, brittle stars) Ask them to identify the evolutionary relationship between echinoderms and chor-

Phylum Figure 2 Evolution of dates—did one evolve from the Chordata Echinodermata chordates and echinoderms. other? (Echinoderms and chordates This shows evolved from a common ancestor that the relationship of the major Ancestral was neither an echinoderm nor a deuterostome and echinoderm groups. chordate.) LS Visual TAKS 3 Bio 7A (grade 11 only), 7B; Bio 8B The first deuterostomes were marine echinoderms that evolved more than 650 million ago. They were also the first animals GENERAL to develop an . Today, most people are familiar with Group Activity echinoderms known as “,” which are not really fish and are All adult echinoderms more properly called sea stars. In addition to sea stars, many other display pentaradial symmetry. Penta animals commonly seen along the sea shore—sea urchins, sand dol- means “five.” Therefore, echino- lars, and sea cucumbers—are echinoderms. All are marine, and all derms have five or approximately are radially symmetrical as adults. multiples of five arms. Have groups Chordates, as well as a few other small phyla, are also deutero- of students create displays that stomes. ( and all other vertebrates are chordates.) Like the define and model various forms of echinoderms, chordates have an internal . This develop- symmetry. Encourage them to com- mental similarity unites these seemingly dissimilar animal phyla. It pare objects made by humans with also leads scientists to believe that chordates and echinoderms those found in nature. They can use derived from a common ancestor, as shown in the phylogenetic tree pictures and clay models to make in Figure 2. The identity of the ancestral deuterostome is not known. The record indicates that echinoderms, such as the their comparisons. sea lily in Figure 3, were abundant in the ancient . LS Kinesthetic Co-op Learning Bio 5C

Evolutionary Milestone Demonstration Display any echinoderms you or 8 Deuterostomes your students may have collected Echinoderms are coelomates that have a deuterostome pattern of such as sea stars or sand dollars. embryo development. The same pattern of development occurs in Emphasize the five-part radial sym- the chordates. Figure 3 Fossil sea lily. Sea lilies such as the one metry of the specimens. Point out preserved by this fossil were that during drying, the skin of sand plentiful in the ancient . dollars disintegrates, and only the 693 hard internal skeleton remains. Ask students how echinoderms differ Trends in Medicine from . (Echinoderms have Body Part The importance , no body segments, and of chemical signals in the development of radial symmetry; arthropods have deuterostomes has significant medical implica- , body segments, and tions for the regeneration of lost body parts. bilateral symmetry.) LS Visual Scientists are working to discover factors that TAKS 2 Bio 8C; Bio 5C cause cells to change and grow so that some- day it might be possible to re-grow a severed or an amputated limb. Bio/IPC 3C; Bio 5C •Unit 7—Exploring Invertebrates This engaging tutorial introduces students to invertebrate structure and function.

Chapter 31 • Echinoderms and Invertebrate Chordates 693 Modern Echinoderms Many of the most familiar animals seen along the seashore—sea Real stars, sea urchins, sand dollars—are echinoderms. Echinoderms TTeach,each, continuedcontinued Do sand dollars are also common in the deep ocean. While all echinoderms are resemble the sun? marine, the different classes of echinoderms vary considerably in Teaching Tip To the Chumash Indians of the details of their body design. Despite their apparent differences, Tell stu- southern , the all echinoderms share four fundamental characteristics. lines radiating from a sand dents that sea urchins hatch from dollar’s mouth resemble 1. Endoskeleton. Echinoderms have a calcium-rich endoskeleton as microscopic floating larvae. the sun’s rays. Sand dol- composed of individual plates called ossicles . When ossicles These delicate, elegant-looking lars, once plentiful in the first form in young echinoderms, they are enclosed in living tis- creatures have two mirror-image Pacific Ocean, became the sue, so they are a true endoskeleton. Even though the ossicles of Chumash’s symbol adult echinoderms appear to be external, they are covered by a halves, just like beetles, and for the “newborn” . They float for weeks near the sun of the thin layer of skin (although sometimes the skin is worn away). ocean’s surface fanning even tinier winter solstice. In adult sea stars and in many other echinoderms, a large num- organisms into their mouths. Then, ber of these plates are fused together. The fused plates function much like an . They provide sites for - a change occurs. A small bundle of cle attachment and shell-like protection. In most echinoderms, cells inside the organism begin to the plates of the endoskeleton spines that project upward grow. All of the other cells die, and through their skin. the tiny bundle settles to the ocean floor to grow into something that 2. Five-part radial symmetry. All echinoderms are bilaterally sym- metrical as larvae. During their development into adults, the looks like a calcified Koosh Ball larvae’s becomes radially symmetrical. Most adult several inches in diameter. Instead echinoderms, such as the one shown on the left in Figure 4, have of two mirror-image halves (bilat- a five-part body plan with arms that radiate from a central point. eral symmetry) seen in the , However, the number of arms can vary. Echinoderms have no the adult urchin is organized more The term echinoderm is or . Instead, the consists of a central like five equal pie slices (pentara- from the Greek echinos, ring of with branches extending into each of the arms. dial symmetry), a nearly spherical meaning “spiny,” and Although echinoderms are capable of complex response pat- version of its cousin the starfish. derma, meaning “skin.” , each arm acts more or less independently. Many , Adult urchins creep slowly around including sea stars, can regenerate a new arm if a portion of an the ocean bottom using a five- arm is lost. In some species of sea stars, a complete animal can toothed structure to scrape food regenerate from an arm connected to a portion of the central from rocks. Studies of both body disk. However, a complete sea star cannot regenerate from an shape and particularly molecular arm alone. composition indicate that their ancestors were bilateral. Bio 5B, 5C Figure 4 Five-part body plan. The echinoderm five- READING part body plan is easily seen SKILL in this colorful African species. BUILDER Other sea stars, such as Interactive Reading Assign the sunstar, have more than Chapter 31 of the Holt Biology five arms. Guided Audio CD Program to help students achieve greater success in reading the chapter. LS Auditory

pp. 694–695 694 Student Edition TAKS Obj 1 Bio/IPC 2C IPC Benchmark Fact TAKS Obj 2 Bio 8C TAKS Obj 2 Bio 10A Have students locate the element calcium on the periodic TAKS Obj 2 Bio 10B table and state the number of its outer or valence electrons, TAKS Obj 3 Bio 12B bonding pattern, physical properties, and chemical behavior TEKS Bio 8C, 10A, 10B, 12B based on its location on the periodic table. TEKS Bio/IPC 2C TAKS 4 IPC 7D (grade 11 only) Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 12B TAKS Obj 4 IPC 7D TEKS Bio 5B, 5C, 10A, 12B, 12C, 12D, 12E TEKS Bio/IPC 2C TEKS IPC 7D

694 Chapter 31 • Echinoderms and Invertebrate Chordates 3. Water-vascular system. Echinoderms have a water- filled system of interconnected canals and thousands of tiny hollow called a water-vascular system. In some echinoderms, such as the sea star, the tube feet Teaching Tip extend outward through openings in the ossicles. In Strength of Tube Feet Tell stu- some species, each tube foot has a at its tip. dents that the legs of sea stars can Many echinoderms use their tube feet to crawl across be very powerful when working the sea floor. The water-vascular system also functions together. An individual foot can be in feeding and . A sea star can use the hundreds of tube feet on its arms to pull the valves of a pulled off a surface easily. However, bivalve open. Some gas exchange and waste excretion when hundreds of tube feet work takes place through the thin walls of the tube feet. Figure 5 Skin . An together, a sea star can exert echinoderm’s skin gills tremendous strength—enough to 4. Coelomic circulation and respiration. The echinoderm body function as both respiratory pull apart the valves of a or cavity functions as a simple circulatory and respiratory system. and excretory organs. Particles, including respiratory gases, move freely throughout hold the animal to a rock when a the large, fluid-filled coelom. Many echinoderms have skin gills wave pounds on it. that aid respiration and waste removal. Skin gills, shown in TAKS 2 Bio 10A; Bio 5C, 12C Figure 5, are small, fingerlike projections that grow among the echinoderm’s spines. These projections create an increased sur- www.scilinks.org Demonstration GENERAL face area through which respiratory gases can be exchanged. Topic: Echinoderms You can use an ordinary dropper to Skin gills also function as excretory structures, and wastes that Keyword: HX4065 accumulate in them are released into the surrounding water. represent tube feet. Show students that when an ampulla is filling with You can learn more about the structure of one particular echino- water, suction is created at the open derm, the sea star, in Up Close: Sea Star, on the following page. end. When the ampulla is expelling water, the suction is gone, and water leaves the open end. This may be easier for students to see if you Determining How Sea Star of Mollusks add a small amount of glitter to the Species A Species B water. LS Visual Bio 5C Predators Affect Prey 100 Background 2C 12B TAKS 1, TAKS 3 0100010110 75 011101010 Sea stars can be very effective predators, 0010010001001 Determining 1100100100010 and they frequently eat mollusks. The chart 50 0000101001001 1101010100100 at right shows the relative number of two Sea How Predators 0101010010010 species of mollusks before and after the 25 stars 0100010110 Affect Prey introduced 011101010 introduction of a predatory sea star. Study of Percentage 0 0010010001001 TAKS 1 Bio/IPC 2C; TAKS 3 Bio 12B the chart, and answer the Analysis questions. original population 1100100100010 0000101001001 Skills Acquired Time 1101010100100 0101010010010 Analyzing data, Analysis predicting results 1. Compare the relative sizes 3. Critical Thinking the sea star to begin of the two mollusk popula- Analyzing Data When consuming a nonpreferred Teacher’s Notes tions before the introduction the sea star began preying species, even when its pre- Show students a picture of a sea of the sea star. on the nonpreferred species, ferred prey is still present? the preferred species had star eating a mollusk. 2. Identify the preferred prey 5. Critical Thinking dropped to what percent of the sea star, and use the Predicting Outcomes of its original population? Answers to Analysis data presented in the graph Predict the relative abundance to support your answer. 4. Critical Thinking of the two species of mollusks 1. The populations were approxi- Inferring Relationships if the sea star remains in the mately the same size. What factors might cause area indefinitely. 2. Species A; species A’s popula- tion was the first to decline 695 and declined more rapidly than species B’s population. OCEANOGRAPHY 3. about 50 percent CONNECTION 4. Accept any reasonable answer. Along the coast in parts of California and A single consumes more than 5,000 The most obvious factor is Alaska, sea and kelp forests flourish pounds per of , , sea stars, relative abundance— together. What’s the connection? Sea urchins. urchins, and other invertebrates. When 17th- non-preferred prey will be Sea urchins eat giant kelp, and when there are and 18th-century hunters slaughtered otters easier to find as preferred prey enough sea urchins, they can roam the forest for their fur, the kelp forests were decimated. becomes scarce. floor and graze entire forests. Where urchins Kelp populations in many areas have 5. There will be about 10 percent abound, it’s hard for new giant kelp to rebounded since, and once again provide a of the original population of survive and grow. But, otters eat urchins. And home for a wide variety of invertebrates and species A and 25 percent of the where otters are present, urchins have to hole vertebrates, including many fish species. original population of species up in deep crevices to survive. By controlling TAKS 3 Bio 12B; Bio 12C, 12D, 12E B as long as both populations sea urchins, sea otters help kelp forests thrive. continue to reproduce and replace lost individuals.

Chapter 31 • Echinoderms and Invertebrate Chordates 695 Up Close Up Close Sea Star TAKS 2, TAKS 3

Sea Star TAKS 2 Bio 8C, 10A; ● 10B (grade 11 only); TAKS 3 Bio 12B Scientific name: vulgaris Teaching Strategies ● Size: Typically from 15 to 30 cm (6 to 12 in.) in diameter Ask students to explain the ● Range: East coast of North America evolutionary link between sea ● Habitat: Intertidal; often on hard, rocky surfaces stars and chordates. Point out ● : Slow-moving or sessile species, including mollusks, that although the relationship , , and between adult echinoderms and chordates may not be apparent, the of both Characteristics groups have certain develop- mental stages in common. Water-vascular system Tube feet Hundreds of tube feet extend from the bottom of Echinoderms not only share Water enters and leaves the Tube feet the radial canals, and each foot is connected to a waterfilled our deuterostome pattern of system through pores in the sac called an ampulla (am PUHL uh). When water is embryonic development, but (ma druh PAWR it), a pumped from the sacs into the tube feet, they expand out- also have bilateral symmetry sievelike structure that filters out ward. Suckers on the ends of the tube feet attach firmly to large particles. Water then moves solid surfaces. When muscles force water back into the as larvae and endoskeletons into the ring canal and passes ampulla, the tube feet shorten, pulling Asterias forward. as adults. LS Logical into the radial canals. ▲ Ampullae ▲ Radial canal Madreporite Ray (arm) Ring canal SKILL BUILDER Interpreting Visuals Pose the following questions as you discuss the illustration. Anus 1. What makes a tube foot extend? Pyloric ▼ Reproductive organs (contraction of the water-filled ▼ Cardiac stomach ampulla) In most species of Asterias 2.What makes it withdraw? Digestive system The the sexes are separate. The (The ampulla relaxes and refills mouth, located in the center of Central gonads lie at the base of the with water.) the body on the bottom side, disk arms and, when filled with is connected by an esopha- eggs or , may occupy 3. Why can’t sea stars live in terres- gus to a stomach located almost the entire arm. trial environments? (They wouldn’t in the central disc. Dur- Digestive ing feeding, a portion be able to move about because glands of the stomach is they need water to operate their ▼ Skin water vascular system.) thrust out through the mouth. Strong diges- Skin Asterias has a delicate skin 4. Why doesn’t a sea star have a tive juices liquefy the stretched over an endoskeleton head? (A sea star has no brain, so prey, which is then ingested. of spiny plates. it has no need for a head to enclose one.) LS Visual Bio 12C 696

Transparencies Sea Star In addition to asexual TT of a Sea Star reproduction (any arm can regenerate a new pp. 696–697 body as long as part of the central disc is Student Edition present), starfish normally undergo sexual TAKS Obj 2 Bio 8C reproduction. A female sea star can deposit TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 7B as many as 2.5 million eggs at one time. The TAKS Obj 3 Bio 12B eggs are deposited in the water, where they TEKS Bio 7B, 8C, 10A, 12B are fertilized by the sperm of a male sea star. Teacher Edition Bio 12C TAKS Obj 2 Bio 4B, 8C, 10A, 10B TAKS Obj 3 Bio 12B TEKS Bio 4B, 8A, 8C, 10A, 10B, 12B, 12C

696 Chapter 31 • Echinoderms and Invertebrate Chordates Echinoderm Diversity Echinoderms are one of the most numerous of all marine phyla. In the past, they were even more plentiful than they are now. There are Teaching Tip more than 20 extinct classes of echinoderms and an additional six Moving Materials Into and Out classes of living members. As you saw on the phylogenetic tree that appeared earlier in this section, the living classes include sea stars, sea of Cells Tell students that the lilies, brittle stars, sea urchins, and sea cucumbers. The recently dis- exchange of gases occurs on the covered does not appear on the phylogenetic tree because its surface of the sea star because par- relationship to the other echinoderms is not fully understood. ticles tend to move from an area of greater concentration to an area of lower concentration. The uptake Sea Stars Figure 6 Sea star. This sea Sea stars are the echinoderms most familiar to people. Almost all star is using its tube feet to pry of molecules by skin gills species of sea stars are , and they are among the most open the shell of a clam. Then occurs because ocean water contains important predators in many marine . For example, the it will feed on the clam’s soft a greater concentration of oxygen tissues. crown-of-thorns sea star eats polyps. In 1 year, a single crown- molecules than the skin gills con- of-thorns can consume up to 6 m2 of a reef. Over time, this sea star tain. Therefore, oxygen enters the can destroy an entire . Other sea stars prey on skin gills by diffusion. bivalve mollusks, whose shells they pull open with their powerful TAKS 2 Bio 4B tube feet, as shown in Figure 6. The ossicles of many species of sea stars produce pincerlike GENERAL structures called pedicellaria (ped uh suh LAH ree uh). Pedicellaria Demonstration contain their own muscles and nerves, and they snap at anything Invite a marine zoologist or aquar- that touches them. This action prevents small organisms from ium store employee to discuss attaching themselves to the surface of the sea star. echinoderms. If possible, have your guest bring in live specimens or Brittle Stars videotapes to show how echino- The sea star’s relatives, the brittle stars and sea baskets, make up derms move and feed. LS Auditory the largest class of echinoderms. Brittle stars have slender TAKS 2 Bio 8C branched arms that they move in pairs to row along the ocean floor. Their arms break off easily, a fact that gives brittle stars their name. READING Brittle stars and sea baskets live primarily on the ocean bottom, SKILL and they usually hide under rocks or within crevices in coral reefs. BUILDER Although a few species are predators, most brittle stars are filter Figure 7 Feather star. The Paired Summarizing Encourage feeders or feed on food in the ocean sediment. feathery arms of these feather students to pause after each para- stars are adapted for filter graph they read to summarize the feeding. Sea Lilies and Feather Stars main points to a partner. You might The sea lilies and feather stars are the model the technique by having a most ancient and primitive living echino- student read a paragraph out loud derms. They differ from all other living and summarize it. Then have another echinoderms because their mouth is student read the next paragraph and located on their upper, rather than lower, summarize it. You may want to pair surface. Sea lilies are sessile and are ELL students wth native English attached to the ocean floor by a stalk that is about 60 cm (23 in.) long. Feather stars, speakers. English Language Learners shown in Figure 7, use hooklike projec- LS Verbal tions to attach themselves directly to the ocean bottom or a coral reef. They some- times crawl or swim for short distances. 697

INCLUSION REAL WORLD Strategies CONNECTION •Attention Deficit Disorder • Learning Disability Clam farmers see sea stars as a nuisance Have the students download pictures of sea because sea stars devour . In the past, the stars, brittle stars, sea lilies, sea urchins, farmers cut the sea stars into several pieces and sand dollars, and sea cucumbers. Ask the flung them back into the sea. They did not students to create a class poster, echinoderm know that sea stars could regenerate from a notebook, or bulletin board with these pic- severed arm, as long as one piece of the central tures. On index cards, have the students disc was present. The clam farmers were actu- identify each of the echinoderms with their ally making the problem worse! Today, clam scientific name and a brief description as to farmers spread lime on the clam beds. Lime what characteristics they have that deter- kills sea stars but leaves clams unharmed. mines they are echinoderms. TAKS 3 Bio 12B TAKS 2 Bio 8C; Bio 8A

Chapter 31 • Echinoderms and Invertebrate Chordates 697 TTeach,each, continuedcontinued Group Activity Pool Diorama Have students work in small groups to conduct library and/or Internet research on organisms found in tide pools. They can choose whichever ocean coast they prefer for their Figure 8 Sea urchin and sand dollar. Sea urchins Sea urchin study. Instruct them to find out usually live on rocky ocean about the most common kinds of bottoms, while sand dollars animals as well as plants that are live on sandy ocean bottoms. Sea Urchins and Sand Dollars found in the type of tide pool they The sea urchins and sand dollars, shown in Figure 8, lack distinct choose. Ask them to search for pic- arms but have the basic five-part body plan seen in other echino- tures of these organisms in books derms. Both sea urchins and sand dollars have a hard, somewhat or on the Internet. Then have each flattened endoskeleton of fused plates covered with spines protrud- ing from it. The spines provide protection and, in some species of sea group construct a diorama depicting urchins, contain a that causes a severe burning sensation. In the organisms found in the type of some other species of sea urchin, a specialized type of pedicellar- tide pool they have selected. ium contains a used to paralyze prey. Sea urchins are found (Students should find at least several on the ocean bottoms while sand dollars live in sandy areas along kinds of echinoderms, such as sea the sea coast. urchins, sea stars, and starfish; several kinds of mollusks, such as chitins, Sea Cucumbers , whelks, and nudibranchs; Sea cucumbers are soft-bodied, sluglike animals without arms. several kinds of arthropods, including They differ from other echinoderms in that their ossicles are small and barnacles; cnidarians, such and are not fused together. Because of this, the sea ’s long, as sea anemones; tunicates, such as sea cylindrical body is soft. Often the body has a tough, leathery ex- squirts; annelids, such as tube ; terior. The sexes of most sea cucumbers are separate, but some ; fish; water plants; and plank- Figure 9 . species are . ton.) Display the tide pool dioramas When threatened, a sea Sea cucumbers feed by trapping tiny organisms present in the for the whole class to observe. cucumber releases sticky sea water. Their mouth, located at one end of the body, is sur- LS Kinesthetic Co-op Learning threads that entrap its attacker. rounded by several dozen tube feet modified into . The tentacles are covered with a sticky that entraps . Periodically, the sea cucumber draws its tentacles into its mouth and cleans off the plankton and mucus. The tentacles are then coated with a fresh supply of mucus. When threatened, a sea cumber has an unusual means of defending itself. As shown in Figure 9, the sea cucumber can release a number of sticky threads from its anus to entrap its attacker. 698

Cultural IPC Benchmark -Lesson pp. 698–699 Awareness Student Edition California’s Sea Urchin IPC Skill TAKS 4 IPC 9B (grade 11 only) Relate the TAKS Obj 2 Bio 8C A grow- concentration of ions in a solution to physical and TAKS Obj 2 Bio 10A ing demand for traditional Japanese cuisine chemical properties such as pH. Activity Bring in TAKS Obj 3 Bio 7A in the has created a growing samples of sea water and pond or river water. Have TAKS Obj 3 Bio 7B market for California sea urchins. Although students for pH level, electrolytic behavior, dis- TAKS Obj 3 Bio 12B the sea urchins were once considered pests solved oxygen, etc. Then have them compare the TEKS Bio 7A, 7B, 8B, 8C, 10A, 12B by kelp harvesters and sports divers, they results of the both samples and research what sub- Teacher Edition are now commercially harvested. Most of stances are present in that are not present in freshwater. TAKS Obj 2 Bio 8C, 10A California’s sea urchin catch is exported TAKS Obj 3 Bio 7B to . TAKS Obj 4 IPC 9B TEKS Bio 5B, 5C, 7B, 8A, 8B, 8C, 10A TEKS Bio/IPC 3C TEKS IPC 9B

698 Chapter 31 • Echinoderms and Invertebrate Chordates Sea Daisies In 1986, a new class of echinoderm was discovered: strange disk- shaped little animals called sea daisies. Less than 1 cm (0.39 in.) in diameter, these creatures were first found in deep waters off the coast of . Only a few species are known. Sea daisies have five-part radial symmetry but no arms. Their tube feet are Monitoring Water located around the edges of the disk rather than along the radial Quality Bio 3C lines, like they are in other echinoderms. Teaching Strategies Use articles from newspapers and magazines to point out Monitoring Water Quality recent problems and solutions concerning water quality. If possible, visit a water treatment f you were swimming or controlled conditions in a lab. In or have someone from Iin coastal waters, you likely this bioassay, sea urchin sperm such a facility come to school would not be able to detect the and eggs are mixed together with to answer students’ questions. presence of toxic chemicals in the collected samples. After a the water, the sediments, or the short waiting period, scientists Recording water temperature in a Discussion sea life. To help protect humans compare the fertilization success bioassay tank •What is a bioassay? (using and marine organisms, scientists rate in the collected water sam- have to be removed or deconta- living organisms or cell cultures have developed several tests to ples with the fertilization success minated. In the future, it may be monitor marine environments for rate found in control water sam- possible to clean up some pollu- to test for the presence of a potential health hazards. Since ples. If the test samples show a tants by using plants that have substance) sea urchin sperm and eggs are lower fertilization rate, scientists the ability to remove toxic chem- •How can scientists tell if water very sensitive to many pollutants, conclude that toxic contaminants icals from the water they are they are used in one of these are present. growing in. The use of this samples are contaminated? tests, known as the sea urchin process, known as phytoremedi- (Fewer fertilizations occur.) Taking Action fertilization bioassay. (A bioassay ation, in marine environments is •What should happen to com- is the use of a living organism or What happens when the test an exciting new area of research. cell culture to test for the pres- indicates the presence of conta- panies found polluting our ence of a substance.) minants? More specific tests waterways? (Answers will vary may be run to determine exactly but might include fining the Using Sea Urchins what contaminants are present. www.scilinks.org companies and making them Samples of ocean water, sedi- If the toxicity can be traced to Topic: Bioassay ment, and industrial wastes that runoff from a factory or sewage Keyword: HX4019 clean the waterways.) are discharged into the ocean are treatment plant, the plant may be collected regularly from different forced to clean its waste before sites. Then they are tested under discharging it. Sediments may CloseClose Section 1 Review Reteaching Make an illustrated chart of echin- Summarize why echinoderms are considered to TAKS Test Prep In an echinoderm, the oderm classes and the characteristics be more closely related to tunicates, lancelets, functions of a are carried out of each class. Leave some of the and vertebrates than to other animals. 8B 8C by the 10A characteristics blank and have A ossicles. Summarize the four major echinoderm students fill them in. Bio 8A characteristics. 8C B pedicellariae. C coelom. GENERAL Describe how the sea stars use their water- D madreporite. Quiz vascular system to move along the sea floor. 7B 1. The part of the digestive tract 699 that develops at the ______of an animal is determined by Answers to Section Review whether it is a protostome or a 1. Echinoderms and chordates share a common feet, they expand, and suckers attach to the deuterostome. (blastopore) pattern of embryonic development (both are surface. When water reenters the ampulla, the 2.Is the skeleton of an echinoderm deuterostomes), and both have an internal tube feet shorten and pull the sea star forward. more like that of an arthropod skeleton. These similarities suggest that the TAKS 3 Bio 7B or a ? Explain your groups share a common ancestor. 4. A. Incorrect. The ossicles are answer. (a vertebrate because it is TAKS 2 Bio 8C; Bio 8B part of the echinoderm’s skeleton and are an endoskeleton) Bio 5B, 5C 2. All echinoderms have an endoskeleton composed not involved in circulation. B. Incorrect. of ossicles, five-part radial symmetry, a water- Pedicellariae are part of the skeletal system Alternative filled vascular system, and coelomic circulation and are not involved in circulation. C. Correct. Assessment GENERAL and respiration. TAKS 2 Bio 8C The coelom acts as a circulatory system. Have students write review ques- D. Incorrect. The function in the 3. Water enters the madreporite and travels into tions for a trivia-type game about water vascular system but are not involved in the ring canal and radial canals to the ampulla the groups of echinoderms. of the tube feet. When water enters the tube gas exchange. TAKS 2 Bio 10A

Chapter 31 • Echinoderms and Invertebrate Chordates 699