3. 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: InvertebratesInvertebrates Unit 9: Vertebrates Unit 10: The Human Body

4. 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

5. Table of Contents – pages iv-v 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

6. 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

7. Table of Contents – pages iv-v Unit 8: InvertebratesInvertebrates Chapter 25: What Is an Animal? Chapter 26: Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27: Mollusks and Segmented WormsMollusks and Segmented Worms Chapter 28: Arthropods Chapter 29: Echinoderms and Invertebrate Chordates

8. 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

9. Unit Overview – pages 670-671 Invertebrates What Is an animal? Sponges, Cnidarians, Flatworms, and Roundworms Mollusks and Segmented Worms Arthropods Echinoderms and Invertebrate Chordates

10. Chapter Contents – page Chapter 27 Introduction: Mollusks an Segmented WormsIntroduction: Mollusks an Segmented Worms 27.1: MollusksMollusks 27.1: Section CheckSection Check 27.2: Segmented WormsSegmented Worms 27.2: Section CheckSection Check Chapter 27 SummarySummary Chapter 27 AssessmentAssessment

11. 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.

12. 27.1 Section Objectives – page 721 Identify the characteristics of mollusks. Section Objectives: Compare the adaptations of gastropod, bivalve, and cephalopod mollusks in their biomes.

13. Section 27.1 Summary – pages 721-727 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. What is a mollusk?

14. Section 27.1 Summary – pages 721-727 Some mollusks have shells, and others, including slugs and squids, are adapted to life without a hard covering. What is a mollusk?

15. Section 27.1 Summary – pages 721-727 All mollusks have bilateral symmetry, a coelom, a digestive tract with two openings, a muscular foot, and a mantle. What is a mollusk? Visceral mass Mantle Shell Foot Tentacle Arm Head Reduced internal shell Mantle Gut Squid

16. Section 27.1 Summary – pages 721-727 The mantle (MAN tuhl) is a membrane that surrounds the internal organs of the mollusk. In shelled mollusks, the mantle secretes the shell. What is a mollusk? Visceral mass Mantle Shell Foot Head Mantle Gut Shell Foot Snail

17. Radula Section 27.1 Summary – pages 721-727 Snails, like many mollusks, use a rasping structure called a radula to obtain food. 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. How mollusks obtain food

18. 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.

19. Section 27.1 Summary – pages 721-727 Bivalves do not have radulas; they filter food from the water. How mollusks obtain food

20. Section 27.1 Summary – pages 721-727 Mollusks reproduce sexually and most have separate sexes. Many gastropods that live on land, and a few bivalves, are hermaphrodites and produce both eggs and sperm. Fertilization is internal. In most aquatic species, eggs and sperm are released at the same time into the water, where external fertilization takes place. Reproduction in mollusks

21. Section 27.1 Summary – pages 721-727 Some marine mollusks have free swimming larvae that propel themselves. Reproduction in mollusks 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.

22. Section 27.1 Summary – pages 721-727 Molusks have simple nervous systems that coordinate their movement and behavior. Nervous control in mollusks Some more advanced mollusks have a brain.

23. Section 27.1 Summary – pages 721-727 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. Nervous control in mollusks

24. Section 27.1 Summary – pages 721-727 Mollusks have a well-developed circulatory system that includes a three-chambered heart. Circulation in mollusks Heart

25. Section 27.1 Summary – pages 721-727 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. Circulation in mollusks

26. Section 27.1 Summary – pages 721-727 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. Circulation in mollusks

27. Section 27.1 Summary – pages 721-727 Most mollusks have respiratory structures called gills. Respiration in mollusks 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.

28. Section 27.1 Summary – pages 721-727 Mollusks are the oldest known animals to have evolved excretory structures called nephridia. Excretion in mollusks 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.

29. Section 27.1 Summary – pages 721-727 Wastes are discharged into the mantle cavity, and expelled from the body by the pumping of the gills. Excretion in mollusks

30. Section 27.1 Summary – pages 721-727 Phylum Mollusca is large and diverse. Diversity of Mollusks Three mollusk classes—Gastropoda, Bivalvia, and Cephalopoda—include the most common and well- known species.

31. Section 27.1 Summary – pages 721-727 The largest class of mollusks is Gastropoda, or the stomach-footed mollusks. Gastropods: One-shelled mollusks The name comes from the way the animal’s large foot is positioned under the rest of its body.

32. Section 27.1 Summary – pages 721-727 Shelled gastropods include snails, abalones, conches, periwinkles, whelks, limpets, cowries, and cones. Gastropods: One-shelled mollusks Instead of being protected by a shell, the body of a slug is protected by a thick layer of mucus.

33. Section 27.1 Summary – pages 721-727 Colorful sea slugs, also called nudibranchs, are protected in another way. Gastropods: One-shelled mollusks

34. Section 27.1 Summary – pages 721-727 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. Gastropods: One-shelled mollusks Any fishes trying to eat the sea slugs are repelled when the nematocysts discharge into the unlucky predator.

35. Section 27.1 Summary – pages 721-727 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. Bivalves: Two-shelled mollusks

36. Section 27.1 Summary – pages 721-727 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. Bivalves: Two-shelled mollusks A ligament, like a hinge, connects their two shells, called valves; strong muscles allow the valves to open and close over the soft body.

37. Section 27.1 Summary – pages 721-727 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. Bivalves: Two-shelled mollusks

38. Section 27.1 Summary – pages 721-727 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. Bivalves: Two-shelled mollusks

39. Section 27.1 Summary – pages 721-727 This class includes the octopus, squid, cuttlefish, and chambered nautilus. Cephalopods: Head-footed mollusks The only cephalopod with a shell is the chambered nautilus, but some species, such as the cuttlefish, have a reduced internal shell.

40. Section 27.1 Summary – pages 721-727 In cephalopods, the foot has evolved into tentacles with suckers, hooks, or adhesive structures. Cephalopods: Head-footed mollusks Cephalopods swim or walk over the ocean floor in pursuit of their prey, capturing it with their tentacles.

41. Section 27.1 Summary – pages 721-727 Once tentacles have captured prey, it is brought to the mouth and bitten with beaklike jaws. Cephalopods: Head-footed mollusks Then the food is torn and pulled into the mouth by the radula.

42. Section 27.1 Summary – pages 721-727 Cephalopods have siphons that expel water. Cephalopods: Head-footed mollusks 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. Water in Water out Direction of squid

43. Section 27.1 Summary – pages 721-727 Squids and octopuses also can release a dark fluid to cloud the water. Cephalopods: Head-footed mollusks This “ink” helps to confuse their predators so they can make a quick escape.

45. Section 1 Check Which of the following mollusks does NOT have a radula, and why? (TX Obj 2; 4B, 8C, 10A, 10B) Question 2 D. slug C. clam B. sea snail A. octopus The answer is C. Clams are filter feeders that do not need a radula to obtain food.

46. Section 1 Check Which of the following is NOT a function of the tentacles of a land snail? (TX Obj 2; 4B, 8C, 10A, 10B) Question 3 D. capturing prey C. moving the eyes B. feeling A. smelling The answer is D, capturing prey.

47. Section 1 Check Which are the first mollusks you would expect to be affected by pollution and why? (TX Obj 2; 4B, 8C, 10A, 10B) Question 4 D. squid C. octopuses B. snails A. clams

48. 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.

49. Section 1 Check Nephridia are organs used for _____. (TX Obj 2; 4B, 8C, 10A, 10B) Question 5 D. excretion C. movement B. respiration A. circulation The answer is D, excretion.

50. 27.2 Section Objectives – page 728 Describe the characteristics of segmented worms and their importance to the survival of these organisms. Section Objectives: Compare and contrast the classes of segmented worms.

51. Section 27.2 Summary – pages 728-733 Segmented worms are classified in the phylum Annelida. They include leeches and bristleworms as well as earthworms. What is a segmented worm? Segmented worms are bilaterally symetrical and have a coelom and two body openings.

52. Section 27.2 Summary – pages 728-733 The basic body plan of segmented worms is a tube within a tube. What is a segmented worm? The internal tube, suspended within the coelom, is the digestive tract.

53. Section 27.2 Summary – pages 728-733 Food is taken in by the mouth, an opening in the anterior end of the worm, and wastes are released through the anus, an opening at the posterior end. What is a segmented worm?

54. Section 27.2 Summary – pages 728-733 Most segmented worms have tiny bristles called setae (SEE tee) on each segment. What is a segmented worm? The setae help segmented worms move by providing a way to anchor their bodies in the soil so each segment can move the animal along. Setae

55. Section 27.2 Summary – pages 728-733 The most distinguishing characteristic of segmented worms is their cylindrical bodies that are divided into ringed segments. Segmentation supports diversified functions In most species, this segmentation continues internally as each segment is separated from the others by a body partition.

56. Section 27.2 Summary – pages 728-733 Each segment has its own muscles, allowing shortening and lengthening of the body. Segmentation also allows for specialization of body tissues. Certain segments have modifications for functions such as sensing and reproduction. Segmentation supports diversified functions

57. Section 27.2 Summary – pages 728-733 Segmented worms have simple nervous systems in which organs in anterior segments have become modified for sensing the environment. Nervous system Some sensory organs are sensitive to light, and eyes with lenses and retinas have evolved in certain species.

58. Section 27.2 Summary – pages 728-733 In some species there is a brain located in an anterior segment. Nervous system Nerve cords connect the brain to nerve centers called ganglia, located in each segment. Setae Nerve Intestine Gizzard Crop Esophagus Mouth Brain Aortic arches

59. Section 27.2 Summary – pages 728-733 Segmented worms have a closed circulatory system. Circulation and respiration Blood carrying oxygen to and carbon dioxide from body cells flow through vessels to reach all parts of the body. Segmented worms must live in water or in wet areas on land because they also exchange gases directly through their moist skin.

60. Section 27.2 Summary – pages 728-733 Segmented worms have a complete internal digestive tract that runs the length of the body. Digestion and excretion Food and soil taken in by the mouth eventually pass to the gizzard.

61. Section 27.2 Summary – pages 728-733 In the gizzard, a muscular sac and hard particles help grind soil and food before they pass into the intestine. Digestion and excretion Mouth Crop Gizzard

62. Section 27.2 Summary – pages 728-733 Undigested material and solid wastes pass out the worm’s body through the anus. Digestion and excretion Segmented worms have two nephridia in almost every segment that collect waste products and transport them through the coelom and out of the body. Nephridia

63. Section 27.2 Summary – pages 728-733 Earthworms and leeches are hermaphrodites, producing both eggs and sperm. Reproduction in segmented worms During mating, two worms exchange sperm. Each worm forms a capsule for the eggs and sperm.

64. Section 27.2 Summary – pages 728-733 The eggs are fertilized in the capsule, then the capsule slips off the worm and is left behind in the soil. Reproduction in segmented worms In two to three weeks, young worms emerge from the eggs.

65. Section 27.2 Summary – pages 728-733 Bristleworms and their relatives have separate sexes and reproduce sexually. Reproduction in segmented worms

66. Section 27.2 Summary – pages 728-733 Usually eggs and sperm are released into the seawater, where fertilization takes place. Reproduction in segmented worms Bristleworm larvae hatch in the sea and become part of the plankton. Once segment development begins, the worm settles to the bottom.

67. Section 27.2 Summary – pages 728-733 The phylum Annelida includes three classes: class Oligochaeta, earthworms; class Polychaeta, bristleworms and their relatives; and class Hirudinea, leeches. Diversity of Segmented Worms

68. Section 27.2 Summary – pages 728-733 Earthworms are the most well-known annelids because they can be seen easily by most people. Earthworms As an earthworm burrows through soil, it loosens, aerates, and fertilizes the soil.

69. Section 27.2 Summary – pages 728-733 Earthworms Mouth Crop Gizzard Setae Nephridia Circulatory system Nervous system

70. Section 27.2 Summary – pages 728-733 The class Polychaeta includes bristleworms and their relatives—fanworms, lug worms, plumed worms, and sea mice. Bristleworms and their relatives

71. Section 27.2 Summary – pages 728-733 Most body segements of a polychaete have many setae, hence the name. Polychaete means “many bristles”. Bristleworms and their relatives Most body segments of a polychaete also have a pair of appendages called parapodia, which can be used for swimming or crawling over corals and the bottom of the sea.

72. Section 27.2 Summary – pages 728-733 Parapodia also function in gas exchange. Bristleworms and their relatives A polychaete has a head with well-developed sense organs, including eyes.

73. Section 27.2 Summary – pages 728-733 Leeches are segmented worms with flattened bodies and usually no setae. Leeches Unlike earthworms, many species are parasites that suck blood or other body fluids from the bodies of their hosts, which include ducks, turtles, fishes, and humans.

74. Section 27.2 Summary – pages 728-733 Front and rear suckers enable leeches to attach themselves to their hosts. Leeches

75. Section 27.2 Summary – pages 728-733 The saliva of the leech contains chemicals that act as an anesthetic. Leeches Other chemicals prevent the blood from clotting. A leech can ingest two to five times its own weight in one meal.

76. Section 27.2 Summary – pages 728-733 Fossil records show that mollusks lived in great numbers as long as 500 million years ago. Gastropod, bivalve, and cephalopod fossils have been found in Precambrian deposits. Origins of Mollusks and Segmented Worms

77. Section 27.2 Summary – pages 728-733 Annelids probably evolved in the sea, perhaps from larvae of ancestral flatworms. Origins of Mollusks and Segmented Worms

78. Section 27.2 Summary – pages 728-733 Tubes constructed by polychaetes are the most common fossils of this phylum. Some of these tubes appear in the fossil record as early as 540 million years ago. Origins of Mollusks and Segmented Worms

79. Section 2 Check Why must segmented worms live in a moist environment? (TX Obj 2; 4B, 8C, 10A, 10B) Question 1 Answer Segmented worms must live in or near water because they exchange gases directly through their moist skin.

80. Section 2 Check During mating, earthworms exchange _____. (TX Obj 2; 4B, 8C, 10A, 10B) Question 2 D. larvae C. capsules containing both sperm and eggs B. sperm A. eggs The answer is B, sperm.

81. Section 2 Check Using this figure, give the reason why you would determine this to be the anterior end of the organism? (TX Obj 2; 4B, 8C, 10A, 10B) Question 3 1 2 3 4 7 6 8 9 10 5 11 13 14 15 16 12 Brain Pharynx Esophagus Blood vessel Crop Nephridia

82. Section 2 Check The anterior portion of an organism would logically include the brain, as well as the initial parts of a gut, like the esophagus and crop (the esophagus and crop are necessary to the initial phases of digestion). 1 2 3 4 7 6 8 9 10 5 11 13 14 15 16 12 Brain Pharynx Esophagus Blood vessel Crop

83. Section 2 Check Which organism would likely get the most use from a gizzard, an earthworm or a leech? (TX Obj 2; 4B, 8C, 10A, 10B) Question 4 Answer A gizzard grinds organic matter into small pieces so the nutrients in the food can be absorbed. Since a leech’s food is liquid (blood), the earthworm would use a gizzard the most, to grind the food and soil it ingests.

84. Section 2 Check Earthworms are considered to be ______. (TX Obj 2; 4B, 8C, 10A, 10B) Question 5 D. grazers C. filter feeders B. parasites A. predators The answer is D, grazers.

85. Chapter Summary – 27.1 Mollusks have bilateral symmetry, a coelom, and a digestive tract with two openings. Many also have shells. Mollusks Most gastropods, such as snails, have a shell, mantle, radula, an open circulatory system, gills, and nephridia. Gastropods without shells, such as slugs, are protected by a covering of mucus.

86. Chapter Summary – 27.1 Bivalve mollusks have paired shells, called valves, and are filter feeders. They have no radula. Clams and scallops are bivalves. Mollusks Cephalopods have tentacles with suckers, beaklike jaws, a mouth with a radula, and a closed circulatory system. Cephalopods include the octopus, squid, and chambered nautilus.

87. Chapter Summary – 27.2 The phylum Annelida includes the earthworms, bristleworms, and their relatives, and leeches. Annelida are bilaterally symmetrical and have a coelom and two body openings; some have larvae that look like the larvae of mollusks. Their bodies are cylindrical and segmented. Segmented Worms Earthworms have complex digestive, excretory, muscular, and circulatory systems.

88. Chapter Summary – 27.2 Bristleworms and their relatives are mostly marine species. They have many setae and parapodia that are used for crawling along. Segmented Worms Leeches are flattened, segmented worms. Most are aquatic parasites. Fossil remains of mollusks show that they first lived over 500 million years ago. Fossil records show that segmented worms first appeared 540 million years ago.

89. Chapter Assessment Question 1 With the exception of slugs, all mollusks that are slow-moving or sessile have shells. Why? (TX Obj 2; 4B, 8C, 10A, 10B)

90. Shells provide organisms with a place to hide that is always near them, since they cannot quickly escape a predator. Chapter Assessment

91. Question 2 Why is a closed circulatory system more efficient than an open circulatory system? (TX Obj 2; 4B, 8C, 10A, 10B)

92. A closed circulatory system is more efficient because blood is transported entirely in closed vessels that can reach deep into the organism’s tissues and provide efficient gas exchange. In an open circulatory system, tissues farthest from the open spaces containing blood are not so likely to be reached for efficient gas exchange. Chapter Assessment

93. Question 3 Why do scientists consider cephalopods to be the most recently evolved of all mollusks? (TX Obj 2; 4B, 8C, 10A, 10B) Answer Cephalopods possess the most complex structures of all mollusks, such as complex eyes, complex brains, closed circulatory systems and feet that have evolved into complex structures like arms and tentacles.

94. Chapter Assessment Question 4 Why are mollusks considered to be excellent index fossils? (TX Obj 2; 4B, 8C, 10A, 10B) Answer Mollusks are generally well preserved in the fossil record, abundant, easy to recognize, and widely distributed geographically.

95. Chapter Assessment Question 5 Which of the following is NOT a food source for humans and why? (TX Obj 2; 4B, 8C, 10A, 10B) A. abalones B. octopuses C. ammonites D. conches The answer is C. Ammonites are not a food source for any organism, because they are extinct.

96. Chapter Assessment Question 6 How does a leech benefit from the chemicals in its saliva that prevent clots from forming? (TX Obj 2; 4B) Answer Preventing blood clots keeps a free flow of blood available to the leech until it is done feeding.

97. Chapter Assessment Question 7 What is the function of parapodia? (TX Obj 2; 4B, 8C, 10A, 10B) Answer Polychaetes use parapodia for swimming, crawling, and for gas exchange.

98. Chapter Assessment Question 8 Why do annelids have such a limited fossil record? (TX Obj 2; 4B, 8C, 10A, 10B) Answer The fossil record for segmented worms is limited because segmented worms have almost no hard body parts from which fossils could develop.

99. Chapter Assessment Question 9 What is the function of setae? (TX Obj 2; 4B, 8C, 10A, 10B) Answer Setae help segmented worms move by providing a way to anchor their bodies in the soil so each segment can move the animal along.

100. Chapter Assessment Question 10 Which of the following features do annelids NOT share with mollusks? (TX Obj 2; 4B, 8C, 10A, 10B) A. coelom B. bilateral symmetry C. digestive tract with two openings D. segmented bodies The answer is D, segmented bodies.

101. Photo Credits General Biololgical Inc. Digital Stock Joey Jacques Corbis PhotoDisc Alton Biggs

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