Reading Essentials for Biology Glencoe (794133), страница 81
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New rays willdevelop to replace thosethat break off.Brittle stars do not use their tube feet for movement. Theymove with a snakelike, slithering motion of their flexible rays.The brittle star uses its tube feet to move bits of food alongthe rays and into its mouth. The mouth is located in the star’scentral disk.MouthReproductiveorganDigestiveglandEndoskeletalplatesWhat are sea urchins and sand dollars?Sea urchins and sand dollars do not have rays. Their shapesresemble globes or disks, and they are covered with spines.
Seaurchins often burrow into rocks to protect themselves from predators and from rough water. A sea urchin resembles a pincushionbecause of its long, pointed spines. The spines help protect thesea urchin from predators. Sea urchins have long and slender tubefeet that help them move.READING ESSENTIALSChapter 29355NameDateClassSection29.1Echinoderms, continued6. Where are the tube feetlocated on a sand dollarand what is their purpose?________________________________________________________________________A sand dollar has a flat surface with a petal-like flower pattern.A living sand dollar is covered with tiny, hair-like spines thatare lost when the animal dies. Like other echinoderms, a sanddollar has tube feet. The tube feet are found on both the upperand lower surface of a sand dollar.
The feet on the upper surfacestick out from the petal-like marks on the sand dollar’s top surface. They are gills used for respiration. Tube feet on the sanddollar’s bottom surface help bring food particles into the sanddollar’s mouth.What are sea cucumbers?What are sea lilies and feather stars?7. Analyze What distinguishes sea lilies andfeather stars from otherechinoderms? (Circle yourchoice.)a. They regenerate.b.
They are sessile.c. They have a larvalstage.356Chapter 29Sea lilies and feather stars are echinoderms. They resembleplants because they have feathery rays. Sea lilies are the only stationary, or sessile, echinoderms. Feather stars are sessile only inthe larval stage. The adult feather star uses its feathery arms toswim from place to place. Sea lilies and feather stars feed by capturing downward-drifting particles with their feathery rays.What are sea daisies?Two species of sea daisies were discovered in 1986 in deepwaters off New Zealand. Sea daisies are flat, disk-shaped echinoderms less than 1 cm in diameter. Sea daisies have tube feet. Thefeet are located around the edge of the disk, not along radial lines.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Sea cucumbers and vegetable cucumbers have a similar shape.Sea cucumbers have a leathery outer covering that allows themthe flexibility needed to move along the ocean floor.
When apredator threatens a sea cucumber, it can protect itself in two ways.It can expel a tangled, sticky mass of tubes through the anus. A seacucumber also may rupture, releasing some of its internal organs.The sticky mass of tubes or the rupturing organs confuse a seacucumber’s predators. This allows the sea cucumber to move awayfrom its predator. The ruptured internal organs regenerate in afew weeks. Sea cucumbers reproduce by shedding sperm and eggsinto the water, where fertilization occurs.NameDateClassSection29.1Echinoderms, continuedOrigins of EchinodermsThe earliest echinoderms may have been bilaterally symmetrical as adults.
They may have been attached to the ocean floor bya kind of stalk. Another view suggests that echinoderms swamfreely in the oceans.Most invertebrates show protostome development. Echinoderms are the only major group of deuterostome invertebrates.Deuterostome development appears mainly in chordates. For thisreason some biologists suggest that echinoderms are the closestinvertebrate relatives of the chordates.Because the endoskeletons are made of calcium carbonate,echinoderms easily turn into fossils.
There is a good fossil recordof the phylum. Echinoderms, as a group, date from the PaleozoicEra. More than 13 000 fossil species have been identified.◗ After You ReadCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Mini Glossaryampulla (AM pew lah): the round, muscularstructure on a tube footrays: the long tapering arms of an echinoderm,especially a sea starmadreporite (mah druh POHR ite): a disk-shapedopening on the upper surface of an echinoderm’s body; operates like a sieve or strainerto keep large particles out of the animaltube foot: a hollow, thin-walled tube that endsin a suction cuppedicellariae (PEH dih sih LAHR ee ay): pincerlikeappendages found on sea stars and seaurchins; used for protection and for cleaning the bodywater vascular system: the system that allowswater to enter and leave the system of a seastar; works as a hydraulic system that operates under water pressure1.
Read the terms and definitions in the Mini Glossary above. Use the space below to write abrief paragraph describing how the parts of an echinoderm work together.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________READING ESSENTIALSChapter 29357NameDateClassSection29.1Echinoderms, continued2. Complete the table below for any three echinoderms that you have read about.
List at leastone characteristic for each echinoderm. Then list at least one way that each is similar to anddifferent from the others.ClassCharacteristicsSimilaritiesDifferencesCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.EchinodermVisit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about echinoderms.358Chapter 29READING ESSENTIALSNameDateClassSection29.2 Invertebrate ChordatesSC.G.1.4.1 The student knows of the great diversity and interdependence of living things.
Also covers SC.D.1.4.4◗ Before You ReadYou are familiar with vertebrates. Cats, dogs, canaries, and humans are vertebrates. Some animals areinvertebrates. What do you think is the primary way in which vertebrates and invertebrates differ?Write your answer on the lines below.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnWhat is an invertebrate chordate?Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.You are probably most familiar with the vertebrate chordates.They have backbones and include animals such as birds, fishes,and mammals.
The phylum Chordata (kor DAH tuh) alsoincludes invertebrates. The three subphyla are listed below.SubphylaMembers of SubphylaUrochordataTunicatesCephalochordataLanceletsVertebrataFishes, reptiles, amphibians, birds, mammalsThis section examines tunicates and lancelets, invertebratechordates that do not have backbones.
Invertebrate chordates donot look much like fishes, reptiles, or humans. However, all ofthese animals have the characteristics common to all chordates. Atsome time during their development, they all have a notochord, adorsal hollow nerve cord, and pharyngeal pouches. In addition, atsome time during their development, all chordates have a postanaltail.
All chordates have bilateral symmetry, aDorsal hollowwell-developed coelom, and segmentation.nerve cordCreate a Quiz After youhave read this section, createa quiz question for each paragraph. After you have writtenthe quiz questions, be sure toanswer them.NotochordWhat is a notochord?The embryos of all chordates have a notochord. The notochord (NOH tuh kord) isa long, semirigid structure that resembles arod.
The notochord is made of large, fluidfilled cells. These cells are held within stiff,fibrous tissues.READING ESSENTIALSAnusMouthMuscle blocksPostanaltailPharyngeal pouchesChapter 29359NameDateClassSection29.2Invertebrate Chordates, continued1. Where is the notochordlocated?________________________________________________________________________Dorsal hollownerve cordThe notochord is located between the digestive system and thedorsal hollow nerve cord.
Invertebrate chordates may keep theirnotochords in their adult stages. In vertebrate chordates, the notochord is replaced by a backbone. Invertebrate chordates do notdevelop a backbone.The notochord develops on what will be the dorsal side of theembryo. It develops after the formation of a gastrula from mesoderm. The gastrula is the embryo development stage in animalswhere cells on one side of the blastula move inward, forming acavity of two or three layers of cells with an opening at one end.The mesoderm is the middle cell layer in the gastrula, betweenthe ectoderm and the endoderm. The notochord holds internalmuscles in place.
This makes it possible for invertebrate chordatesto move their bodies quickly.All chordates have a dorsal hollow nerve cord. In chordates, thedorsal hollow nerve cord develops from a plate of ectoderm thatrolls itself into a hollow tube. This tube is made of cells that surround a fluid-filled canal. The tube lies above the notochord.In most adult chordates, the cells in the posterior or back portion of the dorsal hollow nerve cord develop into the spinal cord.The cells in the anterior or front portion develop into the brain.A pair of nerves connects the nerve cord to each block of muscles.What is a pharyngeal pouch?All chordates have pharyngeal pouches. The pharyngealpouches of a chordate embryo are paired openings that are locatedin the pharynx.
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