Animals pt1


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  • How do hydras ( left, Hydra ) differ from crayfish ( center , green crayfish, Barbi ) and humans ( right , Homo )? They are all multicellular heterotrophic organisms but differ according to their level of organization (hydras have only tissues but crayfishes and humans have organ systems); symmetry (hydras are radially symmetrical but crayfish and humans are bilaterally symmetrical with cephalization); and body plan (hydras have a sac body plan while crayfish and humans have a tube-within-a-tube body plan).
  • All animals are believed to be descended from protists; the Porifera (sponges) with the cellular level of organization may have evolved separately.
  • Mesoderm is the third germ layer.
  • Radially symmetrical animals tend to be sessile. This type of symmetry is useful because it allows these animals to reach out in all directions from one center. Bilaterally symmetrical animals tend to be active and to move forward with an anterior end.
  • When the first embryonic opening becomes the mouth, the coelomate is a protostome. When the first opening is the anus and the second opening becomes the mouth, the animal is a deuterostome.
  • In a sponge, the body wall contains two layers of cells: the outer epidermal cells and the inner collar cells. The collar cells (enlarged) have flagella that beat, moving the water through pores as indicated by the small black arrows in the figure at left. Food particles in the water are trapped by the collar cells and digested within their food vacuoles. Amoeboid cells transport nutrients from cell to cell; spicules form an internal skeleton in some sponges.
  • a. The life cycle of a cnidarian. Some cnidarians have both a polyp and a medusa stage; in others, one form is dominant, and in still others, one form is absent altogether. b. The anemone, which is sometimes called the flower of the sea, is a solitary polyp. c. Corals are colonial polyps residing in a calcium carbonate or proteinaceous skeleton. d. Portuguese man-of-war is a colony of modified polyps and medusae. e. True jellyfish undergo a complete life cycle; the photo shows the medusan stage.
  • Center: The body of Hydra is a small tubular polyp whose body contains two tissue layers. Left: Various types of cells in the body wall. Right, top: Cnidocytes are cells that contain nematocysts. Right, bottom: Hydra reproduces asexually by forming outgrowths called buds, which develop into a complete animal.
  • a. The micrograph of Dugesia shows that this flatworm is bilaterally symmetrical and has a head region with eyespots. b. When the pharynx is extended as shown, food is sucked up into a gastrovascular cavity that branches throughout the body. c. The excretory system with flame cells is shown in detail. d. The reproductive system has both male and female organs, and the digestive system has a single opening. e. The nervous system has a ladder-like appearance.
  • Tapeworm reproduction is by many repeating segments called proglottids, each a bag of eggs. Tapeworm integuments resist the hosts’ digestive juices and it absorbs its food.
  • Schistosomiasis, an infection of humans caused by blood flukes, is an extremely prevalent disease in Egypt – especially since the building of the Aswan High Dam. Standing water in irrigation ditches, combined with unsanitary practices, has created the conditions for widespread infection.
  • a. Flatworms have no body cavity, and mesodermal tissue fills the interior space. b. Roundworms have a pseudocoelom, and the body cavity is incompletely lined by mesodermal tissue. In animals that have no other skeleton, a fluid-filled coelom acts as a hydrostatic skeleton. c. Humans are true coelomates, the body is completely lined by mesodermal tissue, and mesentery holds the internal organs in place.
  • a. The roundworm Ascaris. b. Roundworms such as Ascaris have a pseudocoelom and a complete digestive tract with a mouth and an anus. Therefore, roundworms have a tube-within-a-tube body plan. The sexes are separate; this is a male roundworm. c. The larvae of the roundworm Trichinella penetrate striated muscle fibers, where they coil in a sheath formed from the muscle fiber.
  • Good hygiene, proper disposal of sewage, and cooking meat thoroughly usually protect people from parasitic roundworms.
  • Trochophore larvae also have a band of cilia at the midsection.
  • In protostomes, the first embryonic opening, called the blastopore, becomes the mouth.
  • a. A chiton ( Tonicella ) has a flattened foot and a shell that consists of eigfht articulating valves. b. A chambered nautilus ( Nautilus) achieves buoyancy by regulating the amount of air in chambers of its shell. c. A scallop ( Pecten ) has sensory tentacles extended between the valves. d. A nudribranch (sea slug - Flabellina ) lacks a shell, gills, and a mantle cavity. Dorsal projections function in gas exchange.
  • Table 30.1 (page 622) compares the features of clams a squids.
  • The shell and the mantle have been removed from one side of this clam. Trace the path of food from the incurrent siphon past the gills, to the mouth, the stomach, the intestine, the anus, and the excurrent siphon. Locate the three ganglia: anterior, foot, and posterior. The heart lies in the reduced coelom.
  • Each segment of an earthworm has its own set of longitudinal and circular muscles and its own nerve supply, so each segment or group of segments can function independently.
  • a. Clam worms are predaceous polychaetes that undergo cephalization. Note also the parapodia, which are use for swimming and as respiratory organs. b. Fan worms (a type of tube worm) are sessile filter feeders whose ciliated tentacles spiral in this example.
  • External segmentation reflects a coelom divided by septa. The brain connects to the ventral nerve chord with a lateral nerve on most segments. Nephridia in most segments remove wastes.
  • The top diagram shows the external anatomy of an earthworm. Note the clitellum. The bottom diagram is a cross section of an earthworm showing the internal anatomy and how the setae project through the body wall.
  • When earthworms mate, they are held in place by a mucus secreted by the clitellum. The worms are hermaphroditic, and when mating, sperm pass from the seminal vesicles of each to the receptor vesicles of the other.
  • The Health Focus (page 625) discusses the medicinal value of leeches.
  • Over one million species of arthropods have been described but many more may exist. Each of the five major groups of arthropods contains species that are adapted to terrestrial life. The exoskeleton contains chitin.
  • a. A millipede (flat-backed millipede, Sigmoria ) has only one pair of antennae, and the head is followed by a series of segments, each with two pairs of appendages. b. The hairy tarantulas of the genus Aphonopelma are dark in color and sluggish in movement. Their bite is harmless to people. c. A crab (dungeness crab, Cancer ) is a crustacean with a calcified exoskeleton, one pair of claws and four other pairs of walking legs. d. A wasp (paper wasp, Polistes ) is an insect with two pairs of wings, both used for flying, and three pairs of walking legs. e. A centipede (stone centipede, Lithobius ) has only one pair of antennae, and the head is followed by a series of segments, each with a single pair of appendages.
  • a. Externally, it is possible to observe the jointed appendages, including the swimmerets, the walking legs, and the claws. These appendages, plus a portion of the carapace, have been removed from the right side so the gills are visible. b. Internally, the parts of the digestive system are particularly visible. The circulatory system can also be clearly seen. Note the ventral solid nerve cord.
  • a. Walking sticks ( Diapheromera ) are herbivorous, with biting and chewing mouthparts. b. Bees ( Apis ) have four translucent wings and a thorax separated from the abdomen by a narrow waist. c. Flies (housefly, Musca ) have a single pair of wings and lapping mouthparts. d. Dragonflies ( Aeshna ) have two pairs of similar wings. They catch and eat other insects while flying. e. Butterflies (American copper butterfly, Lycaena ) have forewings larger than their hindwings. Their mouthparts form a long tube for siphoning up nectar from flowers.
  • a. Externally, the tympanum receive sound waves, and the hopping legs and the wings are for locomotion. b. Internally, the digestive system is specialized. The Malpighian tubules excrete a solid nitrogenous waste (uric acid). A seminal receptacle receives sperm from the male, which has a penis.
  • Chiggers are the larvae of certain mites that feed on the skin of vertebrates.
  • a. A scorpion (Kenyan giant scorpion, Pandinus ) has pincerlike chelicerae and pedipalps; its long abdomen ends with a stinger that contains venom. b. Most spiders are harmless, but the venom of the black widow spider ( Latrodectus ) is harmful to humans. c. In the western United States, the wood tick ( Ixodes ) carries a debilitating diseases called Rocky Mountain spotted fever. d. Arachnids breathe by means of book lungs, in which the “pages” are double sheets of thin tissue (lamellae).
  • Animals pt1

    1. 1. Chapter 30: Animals: Part I 30- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction o display.
    2. 2. Evolution and Classification of Animals <ul><li>Animals are multicellular heterotrophs that ingest their food. </li></ul><ul><li>Animals belong to the Eukarya and kingdom Animalia . </li></ul><ul><li>In general, animals have some form of locomotion and have tissues and organs. </li></ul><ul><li>The adult is typically diploid and practices sexual reproduction. </li></ul><ul><li>An embryonic stage undergoes development. </li></ul>30-
    3. 3. Evolution of Animals <ul><li>It is difficult to trace the complete evolutionary tree of animals because soft-bodied animals are poorly preserved as fossils. </li></ul><ul><li>All animals probably evolved from a protistan ancestor. </li></ul><ul><li>All the major animal phyla include some invertebrates , animals without backbones. </li></ul><ul><li>The phylum Chordata is mainly composed of vertebrates . </li></ul>30-
    4. 4. Animal diversity 30-
    5. 5. Criteria for Classification <ul><li>The classification of animals is based on the level of organization or number of germ layers, symmetry, type of coelom, body plan, and presence or absence of segmentation. </li></ul><ul><li>An evolutionary tree based on these features depicts a possible evolutionary relationship between the animals. </li></ul>30-
    6. 6. Evolutionary tree 30-
    7. 7. <ul><li>Level of Organization </li></ul><ul><li>Animals can have the cellular level , the tissue level , or the organ level of organization. </li></ul><ul><li>One of the main events during animal development is the establishment of germ layers . </li></ul><ul><li>If two germ layers (ectoderm and endoderm) are present, then the animal has the tissue level of organization; if all three germ layers are present, the organ level of organization is attained. </li></ul>30-
    8. 8. <ul><li>Type of Body Plan </li></ul><ul><li>Two body plans are present in the animal kingdom: the sac plan and tube-within-a-tube plan. </li></ul><ul><li>Animals with a sac plan have an incomplete digestive system with only one opening. </li></ul><ul><li>Animals with the tube-within-a-tube plan have a complete digestive system. </li></ul><ul><li>Two openings allows for specialization along the length of the tube. </li></ul>30-
    9. 9. <ul><li>Type of Symmetry </li></ul><ul><li>Animals can be asymmetrical, radially symmetrical, or bilaterally symmetrical. </li></ul><ul><li>Asymmetrical animals have no particular symmetry. </li></ul><ul><li>Radial symmetry means the animal is organized similar to a wheel. </li></ul><ul><li>Bilateral symmetry means the animal has definite right and left halves. </li></ul><ul><li>Bilateral symmetry leads to cephalization. </li></ul>30-
    10. 10. 30-
    11. 11. <ul><li>Type of Coelom </li></ul><ul><li>A true coelom (in coelomates ) is an internal body cavity completely lined with mesoderm, where internal organs are found. </li></ul><ul><li>Coelomates are either protostomes or deuterostomes. </li></ul><ul><li>Acoelomates have mesoderm but no body cavity. </li></ul><ul><li>Animals that have a pseudocoelom have a body cavity incompletely lined with mesoderm. </li></ul>30-
    12. 12. <ul><li>Segmentation </li></ul><ul><li>Segmentation is the repetition of body parts along the length of the body. </li></ul><ul><li>Animals can be segmented or nonsegmented. </li></ul><ul><li>Segmentation leads to specialization of parts because the various segments can become differentiated for specific purposes. </li></ul>30-
    13. 13. Introducing the Vertebrates <ul><li>Sponges are asymmetrical. </li></ul><ul><li>Cnidarians have radial symmetry. </li></ul><ul><li>All other phyla contain bilaterally symmetrical animals. </li></ul><ul><li>Flatworms have three germ layers but no coelom. </li></ul><ul><li>Roundworms have a pseudocoelom and a tube-within-a-tube body plan. </li></ul>30-
    14. 14. Sponges <ul><li>Sponges are mainly marine animals at the cellular level of organization. </li></ul><ul><li>The sponge body wall has an outer layer of epidermal cells; a middle layer consisting of semi-fluid matrix where amoeboid cells transport nutrients, produce spicules , and form sex cells; and an inner layer of collar cells with flagella that wave water through pores and out an osculum . </li></ul>30-
    15. 15. <ul><li>Collar cells also engulf food particles and pass them to amoeboid cells. </li></ul><ul><li>Sponges are classified according to type of spicules . </li></ul><ul><li>Chalk sponges have spicules made of calcium carbonate; glass sponges have spicules that contain silica. </li></ul><ul><li>Most sponges also contain spongin fibers made of collagen. </li></ul><ul><li>Sponges are sessile filter feeders. </li></ul><ul><li>They reproduce asexually by budding or by fragmentation . </li></ul>30-
    16. 16. Sponge 30-
    17. 17. Cnidarians <ul><li>Cnidarians are mostly coastal marine animals with a tissue level of organization and radial symmetry. </li></ul><ul><li>They may be a polyp or a medusa or may alternate between the two forms. </li></ul><ul><li>They have cnidocytes that discharge stinging nematocysts , long threads that may have spines and contain a poison. </li></ul><ul><li>Cnidarians are diverse and include sea anemones, coral, and jellyfishes. </li></ul>30-
    18. 18. Cnidarian diversity 30-
    19. 19. <ul><li>Hydra </li></ul><ul><li>A hydra polyp has an outer layer of epidermis derived from ectoderm and an inner layer called gastrodermis derived from endoderm. </li></ul><ul><li>Mesoglea lies between the two layers and contains a nerve net that communicates with muscle fibers so that the animal is able to move. </li></ul><ul><li>Digestion begins in a gastrovascular cavity and finishes in gastrodermal cells . </li></ul><ul><li>Nutrients and gases are distributed from layer to layer by diffusion. </li></ul>30-
    20. 20. Anatomy of Hydra 30-
    21. 21. Flatworms <ul><li>Flatworms are characterized by the tissue level of organization and a sac body plan. </li></ul><ul><li>These acoelomates have three germ layers, and have all organs except respiratory and circulatory organs. </li></ul><ul><li>The flat body facilitates diffusion of oxygen and other molecules from cell to cell. </li></ul>30-
    22. 22. <ul><li>Planarians </li></ul><ul><li>Planarians are freshwater, free living, flatworms. </li></ul><ul><li>Flame cells function in excretion. </li></ul><ul><li>The small brain extends to a ladder arrangement of nerves. </li></ul><ul><li>Light-sensitive organs (eyespots) are in the head; planarians exhibit cephalization . </li></ul><ul><li>One organism has both male and female sex organs – they are hermaphroditic . </li></ul>30-
    23. 23. Planarian 30-
    24. 24. <ul><li>Parasitic Flatworms </li></ul><ul><li>Flukes and tapeworms are two classes of parasitic flatworms; both have intermediate hosts. </li></ul><ul><li>Flukes are oval to elongate and have suckers at the anterior end. </li></ul><ul><li>Blood flukes cause schistosomiasis ; other flukes infect the digestive tract, bile duct, and lungs. </li></ul><ul><li>A tapeworm has an anterior scolex with hooks and suckers to hold itself inside the gut. </li></ul>30-
    25. 25. Schistosomiasis 30-
    26. 26. Roundworms <ul><li>Roundworms have the tube-within-a-tube plan; they are prevalent in soil and some parasitize animals and plants. </li></ul><ul><li>The pseudocoelom is a body cavity incompletely lined with mesoderm. </li></ul><ul><li>The fluid-filled interior forms a hydrostatic skeleton . </li></ul><ul><li>Most species of roundworms have separate males and females. </li></ul>30-
    27. 27. Coelom structure and function 30-
    28. 28. <ul><li>Ascaris </li></ul><ul><li>Ascaris larvae are swallowed and burrow through the intestinal wall and make their way through various organs until they reach the lungs. </li></ul><ul><li>In the lungs, they grow in size for 10 days, then move up to the throat, and are then swallowed. </li></ul><ul><li>After they mature in the intestine, females produce eggs that pass out with feces. </li></ul>30-
    29. 29. Roundworm anatomy 30-
    30. 30. <ul><li>Other Roundworms </li></ul><ul><li>Trichinosis is a roundworm infection from eating undercooked pork containing encysted Trichinella larvae. </li></ul><ul><li>The filarial worm is carried by mosquitoes and causes elephantiasis by blocking lymphatic drainage. </li></ul><ul><li>Pinworms are common infections in children. </li></ul><ul><li>Hookworm is a more serious infection seen in the southern United States. </li></ul>30-
    31. 31. Molluscs <ul><li>Molluscs , along with annelids and arthropods, are protostomes because the first embryonic opening becomes the mouth. </li></ul><ul><li>Because the true coelom form by the splitting of the mesoderm, protostomes are also schizocoelomates . </li></ul><ul><li>Many protostomes also have trochophore (top-shaped) larvae . </li></ul>30-
    32. 32. Protostomes versus deuterostomes 30-
    33. 33. Characteristics of Molluscs <ul><li>A mollusc body typically contains a visceral mass , a mantle , and a foot . </li></ul><ul><li>Molluscan groups are distinguished by a modification of the foot. </li></ul><ul><li>In gastropods , the foot is ventrally flattened. </li></ul><ul><li>In cephalopods , the foot has evolved into tentacles about the head. </li></ul>30-
    34. 34. <ul><li>Squids are cephalopods that display marked cephalization, move rapidly by jet propulsion , and have a closed circulatory system . </li></ul><ul><li>The camera-type eye of cephalopods evolved separately from the eye of vertebrates. </li></ul><ul><li>In cephalopods, the brain is formed from a fusion of ganglia, and nerves leaving the brain supply the body. </li></ul><ul><li>Rapid secretion from an ink gland helps cephalopods escape enemies. </li></ul>30-
    35. 35. Molluscan diversity 30-
    36. 36. <ul><li>Bivalves </li></ul><ul><li>Bivalves , such as clams and relatives, have a hatchet foot and are filter feeders. </li></ul><ul><li>Water enters by an incurrent siphon . </li></ul><ul><li>Food trapped on the gills is swept toward the mouth. </li></ul><ul><li>A coelom is present but reduced. </li></ul><ul><li>The circulatory system pumps blood through sinuses. </li></ul>30-
    37. 37. <ul><li>In bivalves, there is no head and three pairs of ganglia control the bivalve. </li></ul><ul><li>The digestive system of a clam includes a mouth with labial palps , an esophagus, a stomach, and an intestine, which coils about the visceral mass and then is surrounded by the heart as it extends to the anus. </li></ul><ul><li>The anus empties at an excurrent siphon . </li></ul><ul><li>Sexes are usually separate and the gonad is located around the coils of the intestine. </li></ul>30-
    38. 38. Clam 30-
    39. 39. Annelids <ul><li>Annelids are segmented both externally, and internally by partitions called septa . </li></ul><ul><li>Annelids have a hydrostatic skeleton , and partitioning of the coelom permits each body segment to move independently. </li></ul><ul><li>The tube-within-a-tube body plan allows the digestive tract to have specialized organs. </li></ul>30-
    40. 40. <ul><li>Annelids have an extensive closed circulatory system with blood vessels that run the length of the body and branch to every segment. </li></ul><ul><li>The brain is connected to a ventral solid nerve cord with ganglia in each segment. </li></ul><ul><li>The excretory system has nephridia in each segment. </li></ul><ul><li>A nephridium is a tubule that collects wastes and excretes through an opening in the body wall. </li></ul>30-
    41. 41. Marine Worms <ul><li>Polychaetes are marine worms with paddlelike parapodia at the side of each segment. </li></ul><ul><li>Some polychaetes are sessile tube worms . </li></ul><ul><li>A clam worm is a predaceous marine worm with a defined head region. </li></ul><ul><li>During breeding seasons, some worms form sex organs in special segments and shed these segment during breeding. </li></ul>30-
    42. 42. Polychaete diversity 30-
    43. 43. Earthworms <ul><li>Earthworms are oligochaetes having few setae per segment. </li></ul><ul><li>Most scavenge for food in the soil and the moist body wall functions in gas exchange. </li></ul><ul><li>When muscles contract in each segment, setae anchor in the soil, and aid locomotion. </li></ul><ul><li>Five “hearts” pump blood and a branch blood vessel reaches each segment. </li></ul><ul><li>These worms are hermaphroditic. </li></ul>30-
    44. 44. <ul><li>Segmentation in earthworms is evidenced by: </li></ul><ul><li>Body rings </li></ul><ul><li>Coelom divided by septa </li></ul><ul><li>Setae on most segments </li></ul><ul><li>Ganglia and lateral nerves in each segment </li></ul><ul><li>Nephridia in most segments </li></ul><ul><li>Branch blood vessels in each segment </li></ul>30-
    45. 45. Earthworm, Lumbricus 30-
    46. 46. 30-
    47. 47. Leeches <ul><li>Most leeches are fluid feeders that attach themselves to open wounds using suckers. </li></ul><ul><li>Bloodsuckers, such as the medicinal leech, can cut through tissue. </li></ul><ul><li>An anticoagulant ( hirudin ) in their saliva keeps blood from clotting. </li></ul>30-
    48. 48. Arthropods <ul><li>Arthropods are the most varied and numerous of animals. </li></ul><ul><li>The success of arthropods is largely attributable to a flexible exoskeleton , jointed appendages , and specialization of body regions. </li></ul><ul><li>Three body regions – head , thorax , and abdomen – with specialized appendages in each region, and a well-developed nervous system characterize this group. </li></ul>30-
    49. 49. Arthropod diversity 30-
    50. 50. Crustaceans <ul><li>Crustaceans are largely marine and have a head that bears compound eyes, two pair of antennae, and specialized mouth parts. </li></ul><ul><li>Five pairs of walking legs include a first pair of pinching claws. </li></ul><ul><li>In the crayfish, head and thorax are fused into a cephalothorax which is covered on the top and sides by carapace . </li></ul><ul><li>The abdominal segments have swimmerets . </li></ul>30-
    51. 51. <ul><li>The crayfish has an open circulatory system in which the heart pumps blood into a hemocoel consisting of sinuses where the hemolymph flows about the organs. </li></ul><ul><li>Respiration takes place by gills under the hard carapace, and there is a ventral solid nerve cord. </li></ul><ul><li>Sexes are separate in the crayfish. </li></ul>30-
    52. 52. Male crayfish, Cambarus 30-
    53. 53. Insects <ul><li>The head of an insect usually bears a pair of antennae, compound eyes, and simple eyes. </li></ul><ul><li>The thorax bears three pairs of legs and up to two pairs of wings, and the abdomen contains most of the internal organs. </li></ul><ul><li>The insect exoskeleton is lighter and contains less chitin than that of many other arthropods. </li></ul>30-
    54. 54. Insect diversity 30-
    55. 55. <ul><li>Grasshoppers are examples of insects adapted to a terrestrial life; they respire by tracheae and have wings that allow them to evade enemies; the third pair of legs is suitable for jumping. </li></ul><ul><li>There is a tympanum for the reception of sound waves and a male penis for passing sperm to the female without desiccation. </li></ul>30-
    56. 56. <ul><li>Malpighian tubules function in excretion in grasshopper. </li></ul><ul><li>Grasshoppers undergo gradual metamorphosis from nymph to adult. </li></ul><ul><li>Butterflies undergo complete metamorphosis , changing from larva to pupa to adult. </li></ul>30-
    57. 57. Female grasshopper 30-
    58. 58. Arachnids <ul><li>The arachnids include terrestrial spiders, scorpions, ticks, and mites. </li></ul><ul><li>The cephalothorax bears six pairs of appendages: the chelicerae and the pedipalps , and four pairs of walking legs. </li></ul><ul><li>Scorpions are the oldest terrestrial arthropods. </li></ul><ul><li>Ticks and mites are parasitic. </li></ul>30-
    59. 59. <ul><li>Spiders are well-adapted to life on land and have Malphigian tubules – they secrete uric acid, helping to conserve water. </li></ul><ul><li>Spiders spin silk used in various ways. </li></ul><ul><li>Where spiders spin webs, the type of web is a feature that demonstrates the evolutionary relationship among spiders. </li></ul>30-
    60. 60. Arachnid diversity 30-
    61. 61. Chapter Summary <ul><li>Animals are multicellular heterotrophs exhibiting at least some mobility. </li></ul><ul><li>Animals are grouped according to level of organization, symmetry, body plan, pattern of embryonic development, and presence or absence of segmentation. </li></ul><ul><li>Sponges are multicellular with limited mobility and no symmetry. </li></ul>30-
    62. 62. <ul><li>Cnidarians are radially symmetrical with true tissue layers. </li></ul><ul><li>Planarians are bilaterally symmetrical with a definite head region. </li></ul><ul><li>Roundworms have a pseudocoelom and a tube-within-a-tube body plan. </li></ul><ul><li>Molluscs have a muscular foot (variously modified) and a visceral mass enveloped by a mantle. </li></ul>30-
    63. 63. <ul><li>Annelids are segmented with a well developed true coelom. </li></ul><ul><li>Arthropods have jointed appendages and a water-repellent exoskeleton that must be periodically shed. </li></ul><ul><li>Each of the five major groups of arthropods contains species that are adapted to terrestrial life. </li></ul>30-