Table of Contents – pages iv-v Unit 1:What is Biology? Unit 2:Ecology Unit 3: The Life of a Cell Unit 4:Genetics Unit 5:Change Through Time Unit 6:Viruses, Bacteria, Protists, and Fungi Unit 7:Plants Unit 8:Invertebrates Unit 9:Vertebrates Unit 10:The Human Body
Table of Contents – pages iv-v Unit 1: What is Biology? Chapter 1:Biology: The Study of Life Unit 2: Ecology Chapter 2:Principles of Ecology Chapter 3:Communities and Biomes Chapter 4:Population Biology Chapter 5:Biological Diversity and Conservation Unit 3:The Life of a Cell Chapter 6:The Chemistry of Life Chapter 7:A View of the Cell Chapter 8:Cellular Transport and the Cell Cycle Chapter 9:Energy in a Cell
Unit 4: Genetics Chapter 10:Mendel and Meiosis Chapter 11:DNA and Genes Chapter 12:Patterns of Heredity and Human Genetics Chapter 13:Genetic Technology Unit 5: Change Through Time Chapter 14:The History of Life Chapter 15:The Theory of Evolution Chapter 16:Primate Evolution Chapter 17:Organizing Life’s Diversity Table of Contents – pages iv-v
Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18:Viruses and Bacteria Chapter 19:Protists Chapter 20:Fungi Unit 7: Plants Chapter 21:What Is a Plant? Chapter 22:The Diversity of Plants Chapter 23:Plant Structure and Function Chapter 24:Reproduction in Plants Table of Contents – pages iv-v
Table of Contents – pages iv-v Unit 8: Invertebrates Chapter 25:What Is an Animal? Chapter 26:Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27:Mollusks and Segmented Worms Chapter 28:Arthropods Chapter 29:Echinoderms and Invertebrate Chordates
Table of Contents – pages iv-v Unit 9: Vertebrates Chapter 30:Fishes and Amphibians Chapter 31:Reptiles and Birds Chapter 32:Mammals Chapter 33:Animal Behavior Unit 10: The Human Body Chapter 34:Protection, Support, and Locomotion Chapter 35:The Digestive and Endocrine Systems Chapter 36:The Nervous System Chapter 37:Respiration, Circulation, and Excretion Chapter 38:Reproduction and Development Chapter 39:Immunity from Disease
Unit Overview – pages 670-671 Invertebrates What is an animal? Sponges, Cnidarians, Flatworms and Roundworms Mollusks and Segmented Worms Arthropods Echinoderms and Invertebrate Chordates
Chapter Contents – page xi Chapter 29Echinoderms and Invertebrate Chordates 29.1:Echinoderms 29.1:Section Check 29.2:Invertebrate Chordates 29.2:Section Check Chapter 29Summary Chapter 29Assessment
Chapter Intro-page 762 What You’ll Learn You will compare and contrast the adaptations of echinoderms. You will distinguish the features of chordates by examining invertebrate chordates.
29.1 Section Objectives – page 763 Section Objectives: • Compare similarities and differences among the classes of echinoderms. • Interpret the evidence biologists have for determining that echinoderms are close relatives of chordates.
Section 29.1 Summary – pages 763-769 What is an echinoderm? • Echinoderms move by means of hundreds of hydraulic, suction-cup-tipped appendages and have skin covered with tiny, jawlike pincers. • Echinodermsare found in all the oceans of the world.
Section 29.1 Summary – pages 763-769 Echinoderms have endoskeletons • If you were to examine the skin of several different echinoderms, you would find that they all have a hard, spiny,or bumpy endoskeleton covered by a thin epidermis.
Section 29.1 Summary – pages 763-769 Echinoderms have endoskeletons • Sea stars, sometimes called starfishes, may not appear spiny at first glance, but a close look reveals that their long, tapering arms, called rays, are covered with short, rounded spines. • The endoskeleton of all echinoderms is made primarily of calcium carbonate, the compound that makes up limestone.
Section 29.1 Summary – pages 763-769 Echinoderms have endoskeletons • Some of the spines found on sea stars and sea urchins have become modified into pincerlike appendages called pedicellariae (PEH dih sih LAHR ee ay).
Section 29.1 Summary – pages 763-769 Echinoderms have endoskeletons Pedicellariae • An echinoderm uses its jawlike pedicellariae for protection and for cleaning the surface of its body.
Section 29.1 Summary – pages 763-769 Echinoderms have radial symmetry • You may remember that radial symmetry is an advantage to animals that are stationary or move slowly. • Radial symmetry enables these animals to sense potential food, predators, and other aspects of their environment from all directions.
Section 29.1 Summary – pages 763-769 The water vascular system • The water vascular system is a hydraulic system that operates under water pressure. • Water enters and leaves the water vascular system of a sea star through the madreporite (mah druh POHR ite), a sievelike, disk-shaped opening on the upper surface of the echinoderm’s body.
Section 29.1 Summary – pages 763-769 The water vascular system • The underside of a sea star has tube feet that run along a groove on the underside of each ray.
Section 29.1 Summary – pages 763-769 The water vascular system • Tube feet are hollow, thin-walled tubes that end in a suction cup. • Tube feet look somewhat like miniature droppers. • The round, muscular structure called the ampulla (AM pew lah) works something like the bulb of a dropper.
Section 29.1 Summary – pages 763-769 The water vascular system • Each tube foot works independently of the others, and the animal moves along slowly by alternately pushing out and pulling in its tube feet. Ampullae
Section 29.1 Summary – pages 763-769 The water vascular system • Tube feet also function in gas exchange and excretion. Gases are exchanged and wastes are eliminated by diffusion through the thin walls of the tube feet.
Section 29.1 Summary – pages 763-769 Echinoderms have varied nutrition • All echinoderms have a mouth, stomach, and intestines, but their methods of obtaining food vary. • Sea stars are carnivorous and prey on worms or on mollusks such as clams.
Section 29.1 Summary – pages 763-769 Echinoderms have varied nutrition • Most sea urchins are herbivores and graze on algae. • Brittle stars, sea lilies, and sea cucumbers feed on dead and decaying matter that drifts down to the ocean floor.
Section 29.1 Summary – pages 763-769 Echinoderms have a simple nervous system • Echinoderms have no head or brain, but they do have a central nerve ring that surrounds the mouth. Ring canal
Section 29.1 Summary – pages 763-769 Echinoderms have a simple nervous system • Nerves extend from the nerve ring down each ray. • Each radial nerve then branches into a nerve net that provides sensory information to the animal. • Echinoderms have cells that detect light and touch, but most do not have sensory organs.
Section 29.1 Summary – pages 763-769 Echinoderms have a simple nervous system • Sea stars are an exception. A sea star’s body consists of long, tapering rays that extend from the animal’s central disk. • A sensory organ known as an eyespot and consisting of a cluster of light-detecting cells is located at the tip of each arm, on the underside.
Section 29.1 Summary – pages 763-769 Echinoderms have a simple nervous system • Eyespots enable sea stars to detect the intensity of light. • Sea stars also have chemical receptors on their tube feet.
Section 29.1 Summary – pages 763-769 Echinoderms have bilaterally symmetrical larvae • If you examine the larval stages of echinoderms, you will find that they have bilateral symmetry. • Through metamorphosis, the free-swimming larvae make dramatic changes in both body parts and in symmetry.
Section 29.1 Summary – pages 763-769 Echinoderms are deuterostomes • Echinoderms are deuterostomes. • This pattern of development indicates a close relationship to chordates, which are also deuterostomes.
Section 29.1 Summary – pages 763-769 Diversity of Echinoderms • Approximately 6000 species of echinoderms exist today. • About one-fourth of these species are in the class Asteroidea (AS tuh ROY dee uh), to which the sea stars belong.
Section 29.1 Summary – pages 763-769 Diversity of Echinoderms • The five other classes of living echinodems are Ophiuroidea (OH fee uh ROY dee uh),the brittle stars; Echinoidea (eh kihn OY dee uh), the sea urchins and sand dollars.
Section 29.1 Summary – pages 763-769 Diversity of Echinoderms • Holothuroidea (HOH loh thuh ROY dee uh), the sea cucumbers; Crinoidea (cry NOY dee uh), the sea lilies and feather stars; and Concentricycloidea (kon sen tri sy CLOY dee uh), the sea daisies. Sea Cucumber
Section 29.1 Summary – pages 763-769 Sea stars • Most species of sea stars have five rays, but some have more. Some species may have more than 40 rays.
Section 29.1 Summary – pages 763-769 Sea stars Pedicellariae Endoskeleton Ray Madreporite Anus Ring canal Nerve ring Radial canal Stomach Radial nerve Mouth Ampullae Digestive gland Tube feet Reproductive organ Endoskeletal plates Eyespots
Section 29.1 Summary – pages 763-769 Brittle stars • Brittle stars are extremely fragile. • This adaptation helps the brittle star survive an attack by a predator. • While the predator is busy with the broken off ray, the brittle star can escape. A new ray will regenerate.
Section 29.1 Summary – pages 763-769 Brittle stars • Brittle stars propel themselves with the snake like, slithering motion of their flexible rays. • They use their tube feet to pass particles of food along the rays and into the mouth in the central disk.
Section 29.1 Summary – pages 763-769 Sea urchins and sand dollars • Sea urchins and sand dollars are globe or disk-shaped animals covered with spines; they do not have rays. • A living sand dollar is covered with minute, hair-like spines that are lost when the animal dies. • A sand dollar has tube feet that protrude from the petal-like markings on its upper surface.
Section 29.1 Summary – pages 763-769 Sea urchins and sand dollars • These tube feet are modified into gills and are used for respiration. • Tube feet on the animal’s bottom surface aid in bringing food particles to the mouth.
Section 29.1 Summary – pages 763-769 Sea urchins and sand dollars • Sea urchins look like living pincushions, bristling with long, usually pointed spines. • Sea urchins have long, slender tube feet that, along with the spines, aid the animal in locomotion.
Section 29.1 Summary – pages 763-769 Sea cucumbers • Sea cucumbers are so called because of their vegetable-like appearance. • Their leathery covering allows them flexibility as they move along the ocean floor.
Section 29.1 Summary – pages 763-769 Sea cucumbers • When sea cucumbers are threatened, they may expel a tangled, sticky mass of tubes through the anus, or they may rupture, releasing some internal organs that are regenerated in a few weeks. • Sea cucumbers reproduce by shedding eggs and sperm into the water, where fertilization occurs.
Section 29.1 Summary – pages 763-769 Sea lilies and feather stars • Sea lilies and feather stars resemble plants in some ways. • Sea lilies are the only sessile echinoderms. • Feather stars are sessile only in larval form. The adult feather star uses its feathery arms to swim from place to place.
Section 29.1 Summary – pages 763-769 Sea daisies • Sea daisies are flat, disk-shaped animals less than 1 cm in diameter. • Their tube feet are located around the edge of the disk rather than along radial lines, as in other echinoderms.
Section 29.1 Summary – pages 763-769 Origins of Echinoderms • The earliest echinoderms may have been bilaterally symmetrical as adults, and probably were attached to the ocean floor by stalks. • Another view of the earliest echinoderms is that they were bilateral and free swimming.
Section 29.1 Summary – pages 763-769 Origins of Echinoderms • The echinoderms represent the only major group of deuterostome invertebrates. • This pattern of development is one piece of evidence biologists have for placing echinoderms as the closest invertebrate relatives of the chordates.
Section 29.1 Summary – pages 763-769 Origins of Echinoderms • Most echinoderms have been found as fossils from the early Paleozoic Era. • Fossils of brittle stars are found beginning at a later period. Not much is known about the origin of sea daisies.
Section 1 Check Question 1 Why is radial symmetry an advantage to animals that are stationary or slow moving? (TX Obj 2; 8C)
Section 1 Check Radial symmetry enables stationary or slow moving animals to sense potential food, predators, and other aspects of their environment from all directions.
Section 1 Check Question 2 What is the similarity between the endoskeleton of echinoderms and the exoskeleton of crustaceans? (TX Obj 2; 8C, 10A, 10B) Answer Both of these features are composed of calcium carbonate.