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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 33 Invertebrates

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Kingdom Animalia Overview: Life Without a Backbone Invertebrates – Are animals that lack a backbone – Account for 95% of known animal species Figure 33.1

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal phylogeny Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Echinodermata Chordata Figure 33.2

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Porifera Sponges are sessile and have a porous body and choanocytes (Collar cells) Sponges, phylum Porifera

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Porifera · Asymmetrical · Sessile · Filter (Suspension) Feeders · 5000 salt water species 150 fresh water spp · No tissues, organs, or organ systems · Reproduce sexually (Most are hermaphrodites) or asexually (Budding/Fragmentation) · Believed to have evolved from protists

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Porifera Sponges are suspension feeders – Capturing food particles suspended in the water that passes through their body Azure vase sponge (Callyspongia plicifera) Osculum Spicules Water flow Flagellum Collar Food particles in mucus Choanocyte Phagocytosis of food particles Amoebocyte Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes. Spongocoel. Water passing through porocytes enters a cavity called the spongocoel. Porocytes. Water enters the epidermis through channels formed by porocytes, doughnut-shaped cells that span the body wall. Epidermis. The outer layer consists of tightly packed epidermal cells. Mesohyl. The wall of this simple sponge consists of two layers of cells separated by a gelatinous matrix, the mesohyl (“middle matter”). The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes. Amoebocyte. Amoebocytes transport nutrients to other cells of the sponge body and also produce materials for skeletal fibers (spicules) Figure 33.4

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Porifera Choanocytes, flagellated collar cells – Generate a water current through the sponge and ingest suspended food

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cnidaria Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes All animals except sponges – Belong to the clade Eumetazoa, the animals with true tissues Phylum Cnidaria – Is one of the oldest groups in this clade

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cnidaria Radial Symmetry (Diploblastic) Made of only 2 layers of cells (Outer layer for protection, inner layer for digestion) 9000 species e.g. jellyfish, coral, sea anemones, hydra Have two forms (Sessile polyp and mobile medusa) Has a simple nerve net…1 st organized nervous tissue in animals Reproduce sexually and asexually (budding) 1 st predators 1 st digestive cells (Gastrovascular cavity)

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cnidaria The basic body plan of a cnidarian – Is a sac with a central digestive compartment, the gastrovascular cavity A single opening – Functions as both mouth and anus

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cnidaria There are two variations on this body plan – The sessile polyp and the floating medusa Mouth/anus Tentacle Gastrovascular cavity Gastrodermis Mesoglea Epidermis Tentacle Body stalk Mouth/anus Medusa Polyp Figure 33.5

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tentacle “Trigger” Nematocyst Coiled thread Discharge Of thread Cnidocyte Prey Figure 33.6 Cnidaria Cnidarians are carnivores – That use tentacles to capture prey The tentacles are armed with cnidocytes – Unique cells that function in defense and the capture of prey

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cnidaria classes Table 33.1

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cnidaria – Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa (a) These colonial polyps are members of class Hydrozoa. (b) Many species of jellies (class Scyphozoa), including the species pictured here, are bioluminescent. The largest scyphozoans have tentacles more than 100 m long dangling from a bell-shaped body up to 2 m in diameter. (c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison, which can subdue fish and other large prey, is more potent than cobra venom. (d) Sea anemones and other members of class Anthozoa exist only as polyps. Figure 33.7a–d

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CoralAnemone Hydra

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bilateria Most animals have bilateral symmetry The vast majority of animal species belong to the clade Bilateria – Which consists of animals with bilateral symmetry and triploblastic development

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protostome vs Deuterostome Differentiation

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Spiral vs Radial Cleavage

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flatworms Members of phylum Platyhelminthes – Live in marine, freshwater, and damp terrestrial habitats – Are flattened dorsoventrally and have a gastrovascular cavity Although flatworms undergo triploblastic development – They are acoelomates

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flatworms Bilateral symmetry Phylum Platyhelminthes species e.g. Tapeworms, flukes, planaria 1 st animal with nerve cord 1 st animal with defined head (planaria) 1 st animal with a pharynx (throat) Have only one opening to the body (pharynx) Planarians can regenerate (cut in half and each half will regenerate) Reproduce sexually (most are hermaphroditic) or asexually (regeneration)

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flatworms are divided into four classes Table 33.2

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Turbellarian Turbellarians – Are nearly all free-living and mostly marine Figure 33.9

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Planaria The best-known turbellarians, commonly called planarians – Have light-sensitive eyespots and centralized nerve nets Pharynx. The mouth is at the tip of a muscular pharynx that extends from the animal’s ventral side. Digestive juices are spilled onto prey, and the pharynx sucks small pieces of food into the gastrovascular cavity, where digestion continues. Digestion is completed within the cells lining the gastro- vascular cavity, which has three branches, each with fine subbranches that pro- vide an extensive surface area. Undigested wastes are egested through the mouth. Ganglia. Located at the anterior end of the worm, near the main sources of sensory input, is a pair of ganglia, dense clusters of nerve cells. Ventral nerve cords. From the ganglia, a pair of ventral nerve cords runs the length of the body. Gastrovascular cavity Eyespots Figure 33.10

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

25 Flukes Trematodes that parasitize humans – Spend part of their lives in snail hosts

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tapeworm Tapeworms – parasitic – lack a digestive system Proglottids with reproductive structures 200 µm Hooks Sucker Scolex Figure Scolex

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rotifers Rotifers are smaller than many protists – But are truly multi-cellular and have specialized organ systems 0.1 mm Figure st alimentary canal Separate mouth & anus

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rotifers Rotifers have an alimentary canal – A digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom Rotifers reproduce by parthenogenesis – In which females produce more females from unfertilized eggs

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nemerteans Members of phylum Nemertea – Are commonly called proboscis worms or ribbon worms Figure 33.15

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nemerteans The nemerteans unique proboscis – Is used for defense and prey capture – Is extended by a fluid-filled sac Nemerteans also have a closed circulatory system – In which the blood is contained in vessels distinct from fluid in the body cavity – Have no heart

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mollusca Molluscs have a muscular foot, a visceral mass, and a mantle Phylum Mollusca – Includes snails and slugs, oysters and clams, and octopuses and squids Most molluscs are marine – Though some inhabit fresh water and some are terrestrial Molluscs are soft-bodied animals – But most are protected by a hard shell

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phylum Mollusca Bilateral symmetry 3 classes (Gastropoda, Bivalvia, Cephalopoda) Gastropods (Stomach footed) e.g. Periwinkles, slugs, snails, & conches Bivalves (Two shells) e.g. Clams, oysters, and scallops have two shells connected by a ligament Cephalopods (Head footed) e.g. Octopi, Squid Coelomates Have digestive tract with mouth and anus · 1 st animals with simple brain and paired complex eyes · 1 st open circulatory system with 2 or 3 chambered heart · Respiration through gills · Excretion of metabolic wastes through nephridia Reproduce sexually (Many are hermaphroditic)

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Molluscs All molluscs have a similar body plan with three main parts – A muscular foot – A visceral mass – A mantle- Membrane surrounding internal organs

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mollusc Anatomy Visceral mass Mantle Foot Coelom Intestine Gonads Mantle cavity Anus Gill Nerve cords Esophagus Stomach Shell Radula Mouth Nephridium. Excretory organs called nephridia remove metabolic wastes from the hemolymph. Heart. Most molluscs have an open circulatory system. The dorsally located heart pumps circulatory fluid called hemolymph through arteries into sinuses (body spaces). The organs of the mollusc are thus continually bathed in hemolymph. The long digestive tract is coiled in the visceral mass. Radula. The mouth region in many mollusc species contains a rasp-like feeding organ called a radula. This belt of backward- curved teeth slides back and forth, scraping and scooping like a backhoe. The nervous system consists of a nerve ring around the esophagus, from which nerve cords extend. Figure 33.16

35 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mollusca Most molluscs have separate sexes – With gonads located in the visceral mass The life cycle of many molluscs – Includes a ciliated larval stage called a trochophore

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Table Classes of Mollusca

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chitons Class Polyplacophora is composed of the chitons – Oval-shaped marine animals encased in an armor of eight dorsal plates Figure 33.17

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastropods About three-quarters of all living species of molluscs – Belong to class Gastropoda A land snail(a) A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution. (b) Figure 33.18a, b

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastropods Most – Are marine, but there are also many freshwater and terrestrial species – Possess a single, spiraled shell Slugs lack a shell – Or have a reduced shell

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastropods The most distinctive characteristic of this class – Is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head Anus Mantle cavity Stomach Intestine Mouth Figure 33.19

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bivalves Molluscs of class Bivalvia – Include many species of clams, oysters, mussels, and scallops – Have a shell divided into two halves Figure 33.20

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bivalves The mantle cavity of a bivalve – Contains gills that are used for feeding as well as gas exchange Hinge area Gut Coelom Heart Adductor muscle Anus Excurrent siphon Water flow Incurrent siphon Gill Mantle cavity Foot Palp Mouth Shell Mantle Figure 33.21

43 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cephalopods Class Cephalopoda includes squids and octopuses – Carnivores with beak-like jaws surrounded by tentacles of their modified foot

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cephalopods Most octopuses – Creep along the sea floor in search of prey Figure 33.22a (a) Octopuses are considered among the most intelligent invertebrates.

45 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cephalopods Squids use their siphon – To fire a jet of water, which allows them to swim very quickly Figure 33.22b (b) Squids are speedy carnivores with beaklike jaws and well-developed eyes.

46 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ` One small group of shelled cephalopods – The nautiluses, survives today Figure 33.22c (c) Chambered nautiluses are the only living cephalopods with an external shell.

47 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Annelids Are segmented worms Annelids – Have bodies composed of a series of fused rings

48 Phylum Annelida Bilateral symmetry & Coelomates species e.g. Earthworm, leeches Digestive tube with mouth and anus 1 st gizzard (Used to grind food) 1 st developed central nervous system (Ventral nerve cord connects brain to EACH segment) Closed circulatory system Have chaetae (setae) for locomotion Have nephridia to eliminate metabolic waste Reproduce sexually (most are hermaphroditic) Segmentation is important in the evolution of specialized body tissues

49 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

50 The phylum Annelida is divided into 3 classes Table 33.4

51 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oligochaetes Oligochaetes (class Oligochaeta) – Are named for their relatively sparse chaetae, or bristles made of chitin – Include the earthworms and a variety of aquatic species

52 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Annelida Earthworms eat their way through the soil, extracting nutrients as the soil moves through the alimentary canal – Which helps till the earth, making earthworms valuable to farmers

53 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polychaetes Members of class Polychaeta – Possess paddlelike parapodia that function as gills and aid in locomotion Parapodia Figure 33.24

54 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Leeches Members of class Hirudinea – Are blood-sucking parasites, such as leeches Figure 33.25

55 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nematodes Are nonsegmented pseudocoelomates covered by a tough cuticle Among the most widespread of all animals, nematodes, or roundworms – Are found in most aquatic habitats, in the soil, in moist tissues of plants, and in the body fluids and tissues of animals

56 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phylum Nematoda Bilateral symmetry species 1 st tubular digestive system 1 st animal with 2 body openings (mouth & anus) Pseudocoelomates Ascaris – found in soil. Eggs enter human children’s mouth, develop in the intestines, enter the bloodstream and travel to the lungs. Adults are coughed up and swallowed.

57 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ascaris

58 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

59 · Pinworms – Most common roundworm infection in the U.S. Eggs are ingested (usually by children) and develop in the intestines. Adult females exit child’s anus while child sleeps. Symptoms of infection are an itchy anus · Trichinella – Found in undercooked pork Trichinella or wild game

60 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

61 · Hookworm – common in warm climates. Found in contaminated soil and enters the body through the feet when people walk barefooted.

62 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nematoda The cylindrical bodies of nematodes (phylum Nematoda) – Are covered by a tough coat called a cuticle 25 µm Figure 33.26

63 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arthropoda Arthropods are segmented coelomates that have an exoskeleton and jointed appendages Two out of every three known species of animals are arthropods Members of the phylum Arthropoda – Are found in nearly all habitats of the biosphere

64 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings General Characteristics of Arthropods The diversity and success of arthropods – Are largely related to their segmentation, hard exoskeleton, and jointed appendages

65 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arthropods Early arthropods, such as trilobites – Showed little variation from segment to segment Figure 33.28

66 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings · Bilateral symmetry · Coelomates · All are segmented · 1 st animal with jointed appendages · All have an exoskeleton · Exoskeleton pros: External protection, support for muscle attachment · Exoskeleton cons: They are heavy, limit movement, can’t grow, limits size of organism, arthropod must molt [Ecdysis] (New exoskeleton is soft and does not protect against predators) · Have 3 fused body segments (Head, thorax, and abdomen) · Have complete digestive system including specialized mandibles (Jaws) · Have open circulatory system with a heart · Use spiracles and tracheal tubes for respiration

67 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings · · Use malpighian tubules for excretion of metabolic wastes · Nervous system includes brain, nerve cord, simple or compound eyes, and antennae. Simple eyes have one lens, compound eyes have many lenses. Antennae are used to detect motion, sound, and to smell (Pheromones) · Reproduction is sexual (Two types of development: Metamorphosis and Incomplete metamorphosis) · Metamorphosis includes 4 stages (Egg  Larva  Pupa  Adult) · Incomplete metamorphosis includes 3 stages (Egg  Nymph  Adult) · · Evolved from annelids Classes of arthropods include: Arachnida (Spiders, mites, ticks, & scorpions), Crustacea (Crabs, lobsters, shrimp, crayfish, & barnacles), and Insecta

68 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arthropods As arthropods evolved – The segments fused, and the appendages became more specialized The appendages of some living arthropods – Are modified for many different functions Antennae (sensory reception) Head Thorax Swimming appendages Walking legs Mouthparts (feeding) Pincer (defense) Abdomen Cephalothorax Figure 33.29

69 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arthropods The body of an arthropod – Is completely covered by the cuticle, an exoskeleton made of chitin When an arthropod grows – It molts its exoskeleton in a process called ecdysis

70 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arthropods Arthropods have an open circulatory system – In which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs A variety of organs specialized for gas exchange – Have evolved in arthropods

71 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Molecular evidence now suggests – That living arthropods consist of four major lineages that diverged early in the evolution of the phylum Table 33.5

72 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cheliceriforms Cheliceriforms, subphylum Cheliceriformes – Are named for clawlike feeding appendages called chelicerae – Include spiders, ticks, mites, scorpions, and horseshoe crabs

73 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cheliceriformes Most of the marine cheliceriforms are extinct – But some species survive today, including the horseshoe crabs Figure 33.30

74 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger. (a) Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM). (b) Web-building spiders are generally most active during the daytime. (c) 50 µm Figure 33.31a–c Cheliceriformes Most modern cheliceriforms are arachnids – A group that includes spiders, scorpions, ticks, and mites

75 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arachnids Arachnids have an abdomen and a cephalothorax – Which has six pairs of appendages, the most anterior of which are the chelicerae Digestive gland Intestine Heart Stomach Brain Eyes Poison gland Pedipalp Chelicera Book lung Sperm receptacle Gonopore (exit for eggs) Silk gland Spinnerets Anus Ovary Figure 33.32

76 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Myriapods Subphylum Myriapoda – Includes millipedes and centipedes

77 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Myriapods Millipedes, class Diplopoda – Have a large number of legs Each trunk segment – Has two pairs of legs Figure 33.33

78 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Myriapods Centipedes, class Chilopoda – Are carnivores with jaw-like mandibles – Have one pair of legs per trunk segment Figure 33.34

79 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Insects Subphylum Hexapoda, insects and their relatives – Are more species-rich than all other forms of life combined – Live in almost every terrestrial habitat and in fresh water

80 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flight is obviously one key to the great success of insects An animal that can fly – Can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl

81 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Insect Development Many insects – Undergo metamorphosis during their development In incomplete metamorphosis, the young, called nymphs – Resemble adults but are smaller and go through a series of molts until they reach full size

82 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Insect Development Insects with complete metamorphosis – Have larval stages specialized for eating and growing that are known by such names as maggot, grub, or caterpillar The larval stage – Looks entirely different from the adult stage Larva (caterpillar) (a) (b) Pupa (c) Pupa (d) Emerging adult (e) Adult Figure 33.6a–e

83 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Crustaceans While arachnids and insects thrive on land – Crustaceans, for the most part, have remained in marine and freshwater environments

84 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Crustaceans Subphylum Crustacea – Typically have biramous, branched, appendages that are extensively specialized for feeding and locomotion

85 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Crustaceans Decapods are all relatively large crustaceans – And include lobsters, crabs, crayfish, and shrimp Ghost crabs (genus Ocypode) live on sandy ocean beaches worldwide. Primarily nocturnal, they take shelter in burrows during the day. (a) Figure 33.38a

86 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Crustaceans Planktonic crustaceans include many species of copepods – Which are among the most numerous of all animals Planktonic crustaceans known as krill are consumed in vast quantities by whales. (b) Figure 33.38b

87 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Crustaceans Barnacles are a group of mostly sessile crustaceans – Whose cuticle is hardened into a shell The jointed appendages projecting from the shells of these barnacles capture organisms and organic particles suspended in the water. (c) Figure 33.38c

88 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Echinoderms Echinoderms and chordates are deuterostomes

89 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Characteristics of deuterostomes – Radial cleavage – Development of the coelom from the archenteron – Formation of the mouth at the end of the embryo opposite the blastopore

90 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Echinoderms Sea stars and most other echinoderms – Are slow-moving or sessile marine animals A thin, bumpy or spiny skin – Covers an endoskeleton of hard calcareous plates

91 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Echinoderms Unique to echinoderms is a water vascular system – A network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange Stomach Anus Ring canal Gonads Ampulla Podium Radial nerve Tube feet Spine Gills A short digestive tract runs from the mouth on the bottom of the central disk to the anus on top of the disk. The surface of a sea star is covered by spines that help defend against predators, as well as by small gills that provide gas exchange. Madreporite. Water can flow in or out of the water vascular system into the surrounding water through the madreporite. Branching from each radial canal are hundreds of hollow, muscular tube feet filled with fluid. Each tube foot consists of a bulb-like ampulla and suckered podium (foot portion). When the ampulla squeezes, it forces water into the podium and makes it expand. The podium then contacts the substrate. When the muscles in the wall of the podium contract, they force water back into the ampulla, making the podium shorten and bend. Radial canal. The water vascular system consists of a ring canal in the central disk and five radial canals, each running in a groove down the entire length of an arm. Digestive glands secrete digestive juices and aid in the absorption and storage of nutrients. Central disk. The central disk has a nerve ring and nerve cords radiating from the ring into the arms. Figure 33.39

92 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

93 Echinoderms The radial anatomy of many echinoderms – Evolved secondarily from the bilateral symmetry of ancestors

94 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sea Stars Sea stars, class Asteroidea – Have multiple arms radiating from a central disk The undersurfaces of the arms – Bear tube feet, each of which can act like a suction disk (a) A sea star (class Asteroidea) Figure 33.40a

95 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

96 Brittle Stars Brittle stars have a distinct central disk – And long, flexible arms A brittle star (class Ophiuroidea)

97 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sea Urchins and Sand Dollars Sea urchins and sand dollars have no arms – But they do have five rows of tube feet that function in movement (c) A sea urchin (class Echinoidea) Figure 33.40c

98 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sea Cucumbers Sea cucumbers – Upon first inspection do not look much like other echinoderms – Lack spines, and their endoskeleton is much reduced (e) A sea cucumber (class Holothuroidea) Figure 33.40e

99 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chordates – Phylum Chordata – Consists of two subphyla of invertebrates as well as the hagfishes and the vertebrates – Shares many features of embryonic development with echinoderms

100 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A summary of animal phyla Table 33.7


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