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
Invertebrates Unit Overview – pages 670-671 What Is an animal? Sponges, Cnidarians, Flatworms, and Roundworms Mollusks and Segmented Worms Arthropods Echinoderms and Invertebrate Chordates
Chapter Contents – page Chapter 27Introduction: Mollusks an SegmentedWorms 27.1:Mollusks 27.1:Section Check 27.2:Segmented Worms 27.2:Section Check Chapter 27Summary Chapter 27Assessment
Chapter Intro-page 720 What You’ll Learn You will distinguish among the classes of mollusks and segmented worms. You will compare and contrast the adaptations of mollusks and segmented worms.
27.1 Section Objectives – page 721 Section Objectives: • Identify the characteristics of mollusks. • Compare the adaptations of gastropod, bivalve, and cephalopod mollusks in their biomes.
Section 27.1 Summary – pages 721-727 What is a mollusk? • Slugs, snails, squids, and some animals that live in shells in the ocean or on the beach are all mollusks. These organisms belong to the phylum Mollusca. • Although most species live in the ocean, others live in freshwater and moist terrestrial habitats.
Section 27.1 Summary – pages 721-727 What is a mollusk? • Some mollusks have shells, and others, including slugs and squids, are adapted to life without a hard covering.
Section 27.1 Summary – pages 721-727 What is a mollusk? • All mollusks have bilateral symmetry, a coelom, a digestive tract with two openings, a muscular foot, and a mantle. Arm Reduced internal shell Head Mantle Tentacle Gut Squid Visceral mass Shell Mantle Foot
Section 27.1 Summary – pages 721-727 What is a mollusk? • The mantle (MAN tuhl) is a membrane that surrounds the internal organs of the mollusk. In shelled mollusks, the mantle secretes the shell. Mantle Snail Shell Gut Head Foot Shell Visceral mass Foot Mantle
Section 27.1 Summary – pages 721-727 How mollusks obtain food • Snails, like many mollusks, use a rasping structure called a radula to obtain food. Radula • A radula (RA juh luh), located within the mouth of a mollusk, is a tonguelike organ with rows of teeth. The radula is used to drill, scrape, grate, or cut food.
Section 27.1 Summary – pages 721-727 How mollusks obtain food • Octopuses and squids are predators that use their radulas to tear up the food that they capture with their tentacles. • Other mollusks are grazers and some are filter feeders.
Section 27.1 Summary – pages 721-727 How mollusks obtain food • Bivalves do not have radulas; they filter food from the water.
Section 27.1 Summary – pages 721-727 Reproduction in mollusks • Mollusks reproduce sexually and most have separate sexes. • In most aquatic species, eggs and sperm are released at the same time into the water, where external fertilization takes place. • Many gastropods that live on land, and a few bivalves, are hermaphrodites and produce both eggs and sperm. Fertilization is internal.
Section 27.1 Summary – pages 721-727 Reproduction in mollusks • Some marine mollusks have free swimming larvae that propel themselves. • Most marine snails and bivalves have another developmental stage called a veliger in which he beginnings of a foot, shell, and mantle can be seen.
Section 27.1 Summary – pages 721-727 Nervous control in mollusks • Molusks have simple nervous systems that coordinate their movement and behavior. • Some more advanced mollusks have a brain.
Section 27.1 Summary – pages 721-727 Nervous control in mollusks • Most mollusks have paired eyes that range from simple cups that detect light to the complex eyes of octopuses that have irises, pupils, and retinas similar to the eyes of humans.
Section 27.1 Summary – pages 721-727 Circulation in mollusks • Mollusks have a well-developed circulatory system that includes a three-chambered heart. Heart
Section 27.1 Summary – pages 721-727 Circulation in mollusks • In most mollusks, the heart pumps blood through an open circulatory system. • In an open circulatory system, the blood moves through vessels and into open spaces around the body organs.
Section 27.1 Summary – pages 721-727 Circulation in mollusks • Some mollusks, such as octopuses, move nutrients and oxygen through a closed circulatory system. • In a closed circulatory system, blood moves through the body enclosed entirely in a series of blood vessels.
Section 27.1 Summary – pages 721-727 Respiration in mollusks • Most mollusks have respiratory structures called gills. • Gills are specialized parts of the mantle that consist of a system of filamentous projections that contain a rich supply of blood for the transport for gases.
Section 27.1 Summary – pages 721-727 Excretion in mollusks • Mollusks are the oldest known animals to have evolved excretory structures called nephridia. • Nephridia (nih FRIH dee uh) are organs that remove metabolic wastes from an animal’s body. • Mollusks have one or two nephridia that collect wastes from the coelom, which is located around the heart only.
Section 27.1 Summary – pages 721-727 Excretion in mollusks • Wastes are discharged into the mantle cavity, and expelled from the body by the pumping of the gills.
Section 27.1 Summary – pages 721-727 Diversity of Mollusks • Phylum Mollusca is large and diverse. • Three mollusk classes—Gastropoda, Bivalvia, and Cephalopoda—include the most common and well- known species.
Section 27.1 Summary – pages 721-727 Gastropods: One-shelled mollusks • The largest class of mollusks is Gastropoda, or the stomach-footed mollusks. • The name comes from the way the animal’s large foot is positioned under the rest of its body.
Section 27.1 Summary – pages 721-727 Gastropods: One-shelled mollusks • Shelled gastropods include snails, abalones, conches, periwinkles, whelks, limpets, cowries, and cones. • Instead of being protected by a shell, the body of a slug is protected by a thick layer of mucus.
Section 27.1 Summary – pages 721-727 Gastropods: One-shelled mollusks • Colorful sea slugs, also called nudibranchs, are protected in another way.
Section 27.1 Summary – pages 721-727 Gastropods: One-shelled mollusks • When certain species of sea slugs feed on jellyfishes, they incorporate the poisonous nematocysts of the jellyfish into their own tissues without causing these cells to discharge. • Any fishes trying to eat the sea slugs are repelled when the nematocysts discharge into the unlucky predator.
Section 27.1 Summary – pages 721-727 Bivalves: Two-shelled mollusks • Two-shelled mollusks such as clams, oysters, and scallops belong to the class Bivalvia. • Most bivalves are marine, but a few species live in freshwater habitats.
Section 27.1 Summary – pages 721-727 Bivalves: Two-shelled mollusks • Bivalves have no distinct head or radula. Most use their large, muscular foot for burrowing in the mud or sand at the bottom of the ocean or a lake. • A ligament, like a hinge, connects their two shells, called valves; strong muscles allow the valves to open and close over the soft body.
Section 27.1 Summary – pages 721-727 Bivalves: Two-shelled mollusks • One of the main differences between gastropods and bivalves is that bivalves are filter feeders that obtain food by filtering small particles from the surrounding water. • Gill cilia beat to draw water in through an incurrent siphon. • As water moves over the gills, food and sediments become trapped in mucus.
Section 27.1 Summary – pages 721-727 Bivalves: Two-shelled mollusks • Cilia that line the gills push food particles to the mouth. • Large particles, sediment, and anything else that is rejected is transported to the mantle where it is expelled through the excurrent siphon, or to the foot, where it is eliminated from the animal’s body.
Section 27.1 Summary – pages 721-727 Cephalopods: Head-footed mollusks • This class includes the octopus, squid, cuttlefish, and chambered nautilus. • The only cephalopod with a shell is the chambered nautilus, but some species, such as the cuttlefish, have a reduced internal shell.
Section 27.1 Summary – pages 721-727 Cephalopods: Head-footed mollusks • In cephalopods, the foot has evolved into tentacles with suckers, hooks, or adhesive structures. • Cephalopods swim or walk over the ocean floor in pursuit of their prey, capturing it with their tentacles.
Section 27.1 Summary – pages 721-727 Cephalopods: Head-footed mollusks • Once tentacles have captured prey, it is brought to the mouth and bitten with beaklike jaws. • Then the food is torn and pulled into the mouth by the radula.
Section 27.1 Summary – pages 721-727 Cephalopods: Head-footed mollusks • Cephalopods have siphons that expel water. • These mollusks can expel water forcefully in any direction, and move quickly by jet propulsion. Squids can attain speed of 20m per second using this system of movement. Direction of squid Water in Water out
Section 27.1 Summary – pages 721-727 Cephalopods: Head-footed mollusks • Squids and octopuses also can release a dark fluid to cloud the water. • This “ink” helps to confuse their predators so they can make a quick escape.
Section 1 Check Question 2 Which of the following mollusks does NOT have a radula, and why? (TX Obj 2; 4B, 8C, 10A, 10B) A. octopus B. sea snail C. clam D. slug The answer is C. Clams are filter feeders that do not need a radula to obtain food.
Section 1 Check Question 3 Which of the following is NOT a function of the tentacles of a land snail? (TX Obj 2; 4B, 8C, 10A, 10B) A. smelling B. feeling C. moving the eyes D. capturing prey The answer is D, capturing prey.
Section 1 Check Question 4 Which are the first mollusks you would expect to be affected by pollution and why? (TX Obj 2; 4B, 8C, 10A, 10B) A. clams B. snails C. octopuses D. squid
Section 1 Check The answer is A. Clams are filter feeders. They would be most likely to ingest plankton and become polluted. Later, other mollusks like sea snails that prey on clams might ingest the same pollutant when they eat the clams.
Section 1 Check Question 5 Nephridia are organs used for _____. (TX Obj 2; 4B, 8C, 10A, 10B) A. circulation B. respiration C. movement D. excretion The answer is D, excretion.
27.2 Section Objectives – page 728 Section Objectives: • Describe the characteristics of segmented worms and their importance to the survival of these organisms. • Compare and contrast the classes of segmented worms.
Section 27.2 Summary – pages 728-733 What is a segmented worm? • Segmented worms are classified in the phylum Annelida. They include leeches and bristleworms as well as earthworms. • Segmented worms are bilaterally symetrical and have a coelom and two body openings.