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Invertebrates Invertebrates

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  Chapter 33
• Animals that lack a backbone
• Account for 95% of the animal species


                                                  Other bilaterians (including
                                                     Nematoda, Arthropoda,
                                                     Mollusca, and Annelida)



                                  Ancestral colonial
         Figure 33.2
• Exploring invertebrate diversity
                       NEMATODA (25,000 species)                      ARTHROPODA (1,000,000 + species)
                       BRACHIOPODA (335 species)                     NEMERTEA (900 species)

                           PORIFERA (5,500 species)                  CNIDARIA (10,000 species)
                    A roundworm                                           A scorpion (an arachnid)
                  A brachiopod                                                       A ribbon worm
                       CYCLIOPHORA (1 species)                        TARDIGRADA (800 species)
               ACANTHOCEPHALA (1,100 species)                        CTENOPHORA (100 species)
                                                            100 µm
                                   5 mm
                         A sponge                                                   A jelly
                            PLACOZOA (1 species)                         KINORHYNCHA (150
                                          0.5 mm                              species)
                                                   100 µm

                             An acanthocephalan
                    A cycliophoran (colorized SEM)           A ctenophore, or comb jelly
                                                            Tardigrades (colorized SEM)

                                                                        250 µm
                     ONYCHOPHORA (110 species)                 HEMICHORDATA (85 species)
             MOLLUSCA (93,000 species) A placozoan (LM) A kinorhynch (LM)
                                                              ANNELIDA (16,500 species)
                 PLATYHELMINTHES (20,000 species)                       ROTIFERA (1,800

                                         An octopus                                  A marine annelid
                        A species)
             LORICIFERA (10marine flatworm                   A rotifer (LM) (16 species)
                              An onychophoran
                      ECTOPROCTA (4,500 species)            An acorn worm
                                                                 PHORONIDA (20 species)
                               50 µm

                       ECHINODERMATA (7,000 species)                  CHORDATA (52,000 species)

                     Figure 33.3              Ectoprocts Phoronids
            Figure 33.3        A loriciferan (LM)       A priapulan
   Figure 33.3    A sea urchin                                                     A tunicate
         Porifera – Sponges
•   Sessile, porous body, and choanocytes
•   Live in both fresh and marine waters
•   Lack true tissues and organs
•   Water is drawn through the pores into a
    central cavity (spongocoel) and flows out
    through a larger opening (osculum)
•   Suspension feeders -collect food
    particles from water passing through
    food-trapping equipment.
         Porifera – Sponges
• Made up of individual cells
  – Choanocytes – have flagella; trap food
  – Body is made up of two cell layers divided by
    a gel layer (mesohyl)
  – Amoebocytes – cells found in the mesohyl;
    take up food and digest it and then spread the
        Porifera – Sponges
• Most hermaphrodites - each individual
  producing both sperm and eggs
• Have cross fertilization
• Can regenerate
• Hydra, jellyfish
• Radial symmetry
• Gastrovascular cavity - sac with a central
  digestive compartment; acts as a hydroskeleton
• Has two forms – polyps (cyndrical form with
  tentacles) and medusa (flat, mouth down
• Carnivores with tentacles that has cnidocytes
  which contain nemacotcysts (stinging cells)
• Simple body – sac with a cavity
• Single opening – mouth and anus
• Have contractile tissues and merves
  (nerve net)
• No brain
• Classes – hydrozoans, schphozoans,
  cubozoans, and anthozoans
                                           (b) Many species of jellies (class   (c) The sea wasp (Chironex       (d) Sea anemones and other
                                               Scyphozoa), including the            fleckeri) is a member of         members of class Anthozoa
                                               species pictured here, are           class Cubozoa. Its poison,       exist only as polyps.
                                               bioluminescent. The largest          which can subdue fish and
                                               scyphozoans have tentacles           other large prey, is more
         Table 33.1                            more than 100 m long                 potent than cobra venom.
                                               dangling from a bell-shaped
                                               body up to 2 m in diameter.
(a) These colonial polyps are members of
    class Hydrozoa.
Figure 33.7a–d
• Class Hydrozoa
  – Alternate polyp and medusa forms
  – Hydras only in polyp form
     • Reproduces asexually by budding
     • Reproduces sexually by forming
       resistant zygotes that stay dormant
      Hydrozoans Life Cycle
                                                                3 Other polyps, specialized
                       2 Some of the colony’s                  for reproduction, lack                           4 The medusae
                       polyps, equipped with tentacles,        tentacles and produce tiny                       swim off, grow, and
                       are specialized for feeding.            medusae by asexual budding.                      reproduce sexually.

                1 A colony of
                  polyps (inset,                                           Medusa
                      LM) results                                                                                        MEIOSIS
                   from asexual                                                                         Gonad
                     by budding.                                                                       SEXUAL
                                                                                                                                Egg          Sperm

                                       Portion of                         (BUDDING)
                                       a colony
                                       of polyps                                                                                FERTILIZATION



                                                                                                   (larva)                             Key

                                                                                                                                      Haploid (n)
              1 mm                                  6 The planula eventually settles   5 The zygote develops into a                   Diploid (2n)
Figure 33.8                                         and develops into a new polyp.     solid ciliated larva called a planula.
• Class Scyphozoa
  – Mostly medusa
  – Polyp stage is reduced
  – Marine freshwater
• Class Cubozoans
   – Marine
   – Box shaped medusa stage
   – Has complex eyes
   – Very toxic cnidocytes
• Class Anthozoa
   – Sea anemones and corals
   – Occur only as polyps
   – Most sessile
   – Have hard external skeletons
         Bilateral Symmetry
• Most animal species belong to the clade
         phylum Platyhelminthes -
• Live in marine, freshwater, and damp
  terrestrial habitats
• Very thin so all cells interact with the
• Acoelomates
• Gastrovascular cavity with one opening
• Flame bulbs help with excretion

   Table 33.2
      phylum Platyhelminthes -
 • Class Turbellaria
    – Almost all free living & mostly marine
    – Planarians (carnivores that prey on smaller
       • Cilia – help to move over the mucus they secrete
       • Have light-sensitive eyespots and centralized
         nerve nets
       – Lack organs for gas exchange and circulation
       – Asexually by regeneration and sexually b/c
Figure 33.9

     phylum Platyhelminthes -
                1 Mature flukes live in the blood vessels of the human
                  intestine. A female fluke fits into a groove running
                  the length of the larger male’s body, as shown in          Male
                  the light micrograph at right.
• Class Monogenea
  – Parasites in or on animals                                              Female

  – Suckers for attaching to host
             5 These larvae penetrate
               the skin and blood
                                                                            1 mm

                                                                 2 Blood flukes reproduce

  – Ciliated larva starts infection on host
               vessels of humans                                   sexually in the human host.
               working in irrigated                                The fertilized eggs exit the
               fields contaminated                                 host in feces.
               with infected human

• Class Trematoda
                                                                         3 The eggs develop in
                                                                           water into ciliated

  – Parasites to vertebrates                                               larvae. These larvae
                                                                           infect snails, the
                                                                           intermediate hosts.

  – Suckers to attach to host
             4 Asexual reproduction
               within a snail results in
               another type of motile

  – Life cycle – complex and includes
               larva, which escapes from
               the snail host.              Snail host
     Figure 33.11

    intermediate hosts (human and snail)
  – Ex – blood flukes
       phylum Platyhelminthes -
• Class Cestoidea -            – Mature proglottids, loaded
  tapeworms                       with thousands of eggs, are
  – Parasitic in vertebrates      released from the posterior
                                  end of the tapeworm and
  – Lack a digestive
                                  leave with the host’s feces
                               – Eggs ingested by
  – Has suckers and
                                  intermediary hosts, such as
    hooks                                                   Proglottids with
                                  pigs or cattle            reproductive structures

  – Long series of
                                                                           200 µm

                               – The eggs develop into larvae
    proglottids (ribbons)
                                  that encyst in the muscles of
                                          Scolex    Hooks

    sacs of sex organs lie                         Sucker

                                  their host.
                                 Figure 33.12
    posterior to the scolex
    (head)                     – Humans acquire the larvae by
                                  eating undercooked meat
     Phylum Rotifera - Rotifers
• Are tiny animals that inhabit fresh water, the
  ocean, and damp soil
• Multicellular and have specialized organ
• Have an alimentary canal - digestive tube with a
  separate mouth and anus that lies within a fluid-
  filled pseudocoelom
• Figure 33.13
  Have cilia around their mouth and a pharnyx0.1 mm

• Rotifers reproduce by parthenogenesis
  – In which females produce more females from
    unfertilized eggs
• Have a lophophore – circular crown of
  ciliated tentacles around the mouth
• Have a true coelom                Lophophore

• Ectoprocts –
  – Colonial animals
  – In a hard exoskeleton with pores so
    lophophores can extend
                                            Ectoprocts, such as this sea
                                            mat (Membranipora
                               Figure 33.14amembranacea), are colonial
• Phoronids
  – Are tube-dwelling marine worms
  – Live buried in the sand within chitinous tubes
    & extend the lophophore from the tube when
    feeding and pull it back in when threatened

                                 In phoronids such as
                                 Phoronis hippocrepia, the
                                 lophophore and mouth
                                 are at one end of an
                     Figure 33.14b
                                 elongated trunk.
• Brachiopods
  – Resemble clams
  – But the two halves of the shell are dorsal and
    ventral rather than lateral, as in clams
  – Live attached to the substratum by a stalk


                          (c) Brachiopods have a hinged shell.
                              The two parts of the shell are
             Figure 33.14c dorsal and ventral.
• Proboscis worms or ribbon worms
• Structurally - acoelomate
• Small fluid-filled sac
• Sac and fluid act as an extensible probiscus
  which shoots out of the worm’s body delivering a
• Has an alimentary canal
• Have similar excretory, sensory, and nervous
  systems to flatworms
  Figure 33.15
• Have a complete digestive tract and a closed
  circulatory system (blood is contained in
• Have a muscular foot, visceral mass and a
• Snails and slugs, oysters and clams, and
  octopuses and squids
• Soft-bodied animals, but most are protected by a
  hard shell of calcium carbonate
• Some have reduced or lost their shells from
• Similar body plan
   – A muscular foot (typically for locomotion)
   – A visceral mass with most of the internal
   – A mantle (fold of tissue that drapes over the
      visceral mass and secretes a shell)
• If the mantle extends beyond the visceral mass,
  have a mantle cavity (a water filled chamber that
  houses the gills, anus, and excretory pores)
• Radula – rasping organ that scrapes food.
• Most have separate sexes but some are
   – Life cycle includes a ciliated larvae
• Most are open circulatory system with a dorsal
  heart that pumps hemolymph
• There are 4 major classes

       Table 33.3
• Class Polyplacophora - chitons
  –   Oval shaped body
  –   Shells divided into eight dorsal plates
  –   Have an unsegmented body
  –   Found on rocks
• Class Gastropoda
  – Snails and slugs; can be predators
  – Mostly marine but also freshwater and land
  – During embryonic development, gastropods
    undergo torsion (visceral mass is rotated up
    to 180 degrees so the anus and mantle cavity
    are above the head in adults)
  – Protected by single, spiraled shells
  – Have distinct head with eyes at the tips of
• Class Bivalvia
  – Clams, oysters, mussels, and scallops
  – Shells divided into two halves
  – 2 parts are hinged at the mid-dorsal line, and
    powerful adductor muscles close the shell
    tightly to protect the animal.
  – When the shell is open, the bivalve may
    extend its foot for digging or anchoring
  – No distinct head and radula has been lost
  – Has gills with mucus on it to trap food
  – Suspension feeders
  – Water moves through a siphon
         • Class Cephalopoda
              – Exs – squid and octopus
              – Carnivores with beak-like jaws surrounded by
                  tentacles of their modified foot
              – Rapid movements to dart toward their prey
                                             Figure 33.22b
                                                           (b) Squids are speedy
                                                               carnivores with beaklike jaws
                                                               and well-developed eyes.
                  which they capture with several long tentacles
              – A mantle covers the visceral mass, but the
                  shell is reduced and internal in squids,
                  missing in many octopuses
              – Haveinvertebrates.
          (a) Octopuses are considered among the
33.22a        most intelligent a closed circulatory system

              – Well developed sense organs and a complex
       Annelida - Earthworms
• Segmented bodies
• Live in the sea, freshwater habitats, and
  damp soil
• Coelom of the earthworm – separated by
  septa, but the digestive tract, longitudinal
  blood vessels, and nerve cords penetrate
  the septa and run the animal’s length
• Have a digestive system (a pharynx, an
  esophagus, crop, gizzard, and intestine)
• Closed circulatory system
• In each segment - pair of excretory tubes
  (metanephridia) that remove wastes from
  the blood and coelomic fluid
• Brainlike pair of cerebral ganglia
• Cross-fertilizing hermaphrodites - 2
  earthworms exchange sperm and then
  separate. The received sperm are stored
  while the clitellum, secretes a mucous
  cocoon which slides along the body to pick
  up eggs and stored sperm and slides off
  the body into the soil.
• Some reproduce asexually by
  fragmentation followed by regeneration
• Class Oligochaeta
  – Includes earthworms
  – Have chaetae (bristles)
  – As moves through soil eat
  – Undigested food leaves through anus
  – Hermaphrodites
  – Sperm stored in clitellum
  – Closed circulatory system
  – Mouth, pahrynx, crop, gizzard, intestine, anus
  – Cerebral ganglion and nerve cords
• Class Polychaeta
  – Each segment has a pair of paddlelike or
    ridgelike parapodia (“almost feet”) that
    function in movement
  – Each parapodium has chaetae
• Class Hirudinea (leeches)
  – Predators or parasites that suck blood
  – The leech secretes hirudin, an anticoagulant,
    into the wound, allowing the leech to suck as
    much blood as it can hold
•   Roundworms
•   Found in most aquatic habitats
•   Nonsegmented
•   Covered with a tough exoskeleton
    (cuticle); when grows sheds this
•   Muscles are longitudinal
•   Sexual and internal fertilization
•   Decomposition and nutrient cycling
• Body segmentation
• Hard exoskeleton
• Jointed appendages
• Well developed sensory organs (antennae)
• Also have cephalothorax, abdomen, mouthparts
  walking legs and pincers
• Open circulatory system- hemolymph fluid is
  propelled by a heart through short arteries into
  sinuses (hemocoel) surrounding tissues and

               Antennae            Head


                                                           Walking legs

Figure 33.29    Pincer (defense)
                                    Mouthparts (feeding)
Table 33.5
• Subphylum Cheliceriforms
  – Clawlike feeding appendages –chelicerae
  – Include spiders, ticks, mites, scorpions, and
    horseshoe crabs
  – Lack antennae and have simple eyes
  – Modern cheliceriforms - arachnids (spiders,
    scorpions, ticks, and mites)
  – Abdomen and a cephalothorax which has six
    pairs of appendages, the most anterior of
    which are the chelicerae
                Digestive                                                    Brain
                gland                             Heart


                  Ovary                                                                     Poison

                                                          Book lung
                                    Gonopore        Sperm                      Pedipalp
Figure 33.32           Silk gland   (exit for eggs) receptacle
• Subphylum Myriapods
  – Millipedes and centipedes
  – All are terrestrial          Figure 33.33

  – Head has antennae and 3 pairs of
    appendages including a mandible
  – Millipedes – Each segment has 2 pairs of legs
  – Centipedes – each segment has 1 pair of
    legs; carnivores

             Figure 33.34
• Subphylum Hexapoda - Insects
   – Most diverse
   – Diversity related to flowering plants
   – Flight is obviously one key to the great success of
   – Most go through metamorphosis
         • Incomplete – young still looks like adult but
            smaller; different body proportions and no wings
         • Complete – larval stage looks different than adults
     (a) Larva (caterpillar)
   – Sexual reproduction with different sexes
                             (b) Pupa
                                      (c) Pupa
                                               (d) Emerging adult
         • Mostly internal

    Figure 33.6a–e                                (e) Adult
                    The insect body has three regions: head,
                    thorax, and abdomen. The segmentation                                 Cerebral ganglion. The two nerve
                    of the thorax and abdomen are obvious,               Heart. The       cords meet in the head, where the
                    but the segments that form the head are fused.       insect heart     ganglia of several anterior segments
                                                                         drives hemolymph are fused into a cerebral ganglion
                      Abdomen      Thorax    Head                        through an       (brain). The antennae, eyes, and
                                                                         open circulatory other sense organs are concentrated
                                                       Compound eye      system.          on the head.

                                                                                            artery   Crop

                   Malpighian tubules.
                    Metabolic wastes are
                      removed from the        Vagina
               hemolymph by excretory
               organs called Malpighian
                  tubules, which are out-
                       pocketings of the
                          digestive tract.

                Tracheal tubes. Gas exchange in insects is        Nerve cords. The insect   Insect mouthparts are formed from
                accomplished by a tracheal system of branched,    nervous system            several pairs of modified appendages.
                chitin-lined tubes that infiltrate the body and   consists of a pair of     The mouthparts include mandibles,
                carry oxygen directly to cells. The tracheal      ventral nerve cords       which grasshoppers use for chewing.
                system opens to the outside of the body           with several              In other insects, mouthparts are
                through spiracles, pores that can control air     segmental ganglia.        specialized for lapping, piercing, or
                flow and water loss by opening or closing.                                  sucking.
Figure 33.35
• Insects are classified into about 26 orders
                              ORDER              NUMBER OF                                 MAIN CHARACTERISTICS                                         EXAMPLE

                         Lepidoptera            120,000
                                                               Butterflies and moths are among the best-known insects. They
                                                               have two pairs of wings covered with tiny scales. To feed, they
                                                               uncoil a long proboscis. Most feed on nectar, but some species
                                                               feed on other substances, including animal blood or tears.                 Swallowtail
                      ORDER                NUMBER OF                               MAIN CHARACTERISTICS                                        EXAMPLES

                         Odonata        4,000                  Dragonflies and damselflies have two pairs of large, membran-
                                                              Cockroaches have a dorsoventrally flattened body, with legs
                                                               ous wings. They have an elongated abdomen, large, compound
                                                              modified for rapid running. Forewings, when present, are
                                                               eyes, and chewing mouthparts. They undergo incomplete meta-             German
                                                              leathery, whereas hind wings are fanlike. Fewer than 40 cock-
                                                               morphosis and are active predators.                                     cockroach
                                                              roach species live in houses; the rest exploit habitats ranging
                                                              from tropical forest floors to caves and deserts.                                                Dragonfly

                        Orthoptera            13,000
                                                              Grasshoppers, crickets, and their relatives are mostly herbi-
                   Coleoptera           350,000               Beetles comprise the most species-rich order jumping, two
                                                              vorous. They have large hind legs adapted for of insects. They
                                                              have two pairs of wings, one of which is thick and leathery, the
                                                              pairs of wings (one leathery, one membranous), and biting or             Japanese
                                                              other membranous. They have an armored exoskeleton and
                                                              chewing mouthparts. Males commonly make courtship sounds                 beetle
                                                              mouthparts adapted for biting and chewing. Beetles undergo
                                                              by rubbing together body parts, such as a ridge on their hind
                                                              complete metamorphosis.
                                                              leg. Orthopterans undergo incomplete metamorphosis.


                   Dermaptera           1,200                 Earwigs are generally nocturnal scavengers. While some
                         Phasmida               2,600         species are wingless, others have two pairs of wings, one of
                                                              Stick is thick and leathery, the other membranous. Earwigs
                                                              whichinsects and leaf insects are exquisite mimics of plants. The
                                                              eggs of some species even large seeds of the plants on un-
                                                              have biting mouthparts and mimicposterior pincers. They which the
                                                              Insects live. Their body is cylindrical
                                                              dergo incomplete metamorphosis. or flattened dorsoventrally.                           Earwig
                                                              They lack forewings but have fanlike hind wings. Their                        Stick insect
                                                              mouthparts are adapted for biting or chewing.

                   Diptera              151,000               Dipterans have one pair of wings; the second pair has become
                                                              modified into balancing organs called halteres. Their head is
                                                              large and mobile; their mouthparts are adapted for sucking,
                                                              piercing, or lapping. Dipterans undergo complete metamorpho-             Horsefly
                                                              sis. Flies and mosquitoes are among the best-known dipterans,
                         Phthiraptera           2,400         which live as scavengers, predators, and parasites.
                                                                Commonly called sucking lice, these insects spend their entire
                                                                life as an ectoparasite feeding on the hair or feathers of a single
                                                                host. Their legs, equipped with clawlike tarsi, are adapted for             Human
                                                                clinging to their hosts. They lack wings and have reduced eyes.
                   Hemiptera                                                                                                                louse
                                        85,000                  Sucking lice are so-called “true bugs,” including bed bugs,
                                                               Hemipteransundergo incomplete metamorphosis.
                                                               assassin bugs, and chinch bugs. (Insects in other orders are           Leaf-
                                                               sometimes erroneously called bugs.) Hemipterans have two               Footed
                                                               pairs of wings, one pair partly leathery, the other membranous.        bug
                                                               They have piercing or sucking mouthparts and undergo
                         Siphonaptera           2,400          incomplete metamorphosis.
                                                                Fleas are bloodsucking ectoparasites on birds and mammals.
                                                                Their body is wingless and laterally compressed. Their legs are
                                                                modified for clinging to their hosts and for long-distance
                                                                jumping. They undergo complete metamorphosis.
                   Hymenoptera          125,000                                                                                                              Flea
                                                              Ants, bees, and wasps are generally highly social insects. They
                                                              have two pairs of membranous wings, a mobile head, and
                                                              chewing or sucking mouthparts. The females of many species
                         Thysanura              450           have a posterior stinging organ. Hymenopterans undergo com-
                                                               Silverfish are small, wingless insects with a flattened body and
                                                              plete metamorphosis. live in leaf litter or under bark. They can also
                                                               reduced eyes. They                                                          Cicada-killer wasp
                                                               infest buildings, where they can become pests.

                   Isoptera             2,000                                                                                                           Silverfish
                                                              Termites are widespread social insects that produce enormous
                                                              colonies. It has been estimated that there are 700 kg of
                                                              termites for every person on Earth! Some termites have two
                         Trichoptera            7,100         pairs of membranous wings, while others are wingless. They
                                                               The on wood caddisflies of microbial symbionts carried in
                                                              feed larvae of with the aid live in streams, where they make houses
                                                               from sand chambers in their hindgut.
                                                              specializedgrains, wood fragments, or other material held to-                        Termite
                                                               gether by silk. Adults have two pairs of hairy wings and chewing
                                                               or lapping mouthparts. They undergo complete metamorphosis.
   Figure 33.37                                                                                                                                         Caddisfly
    Figure 33.37
• Marine and freshwater
• Have specialized branched appendages
  for feeding and locomotion
• Has 2 antennae
• 3 or more appendages are modified as
  mouthparts including the mandibles
• Have walking legs on their thorax and
  appendages on the abdomen
•   Larger crustaceans have gills for gas exchange
•   Sexes are separate
•   Isopods – found in the deep ocean; pill bugs
•   Decapods - all relatively large crustaceans;
    lobsters, crabs, crayfish, and shrimp
     – Have a cuticle hardened by calcium
• Copepods - Planktonic crustaceans;
  among the most numerous
• Barnacles - mostly sessile crustaceans
  whose cuticle is hardened into a shell
   – Anchored to rocks
   – To feed extend appendages
  Echinoderms and Chordates are
• Echinderms
  – Slow-moving or sessile marine animals
  – Prickly
  – Have a water vascular system - network of
    hydraulic canals branching into tube feet that
    function in locomotion, feeding, and gas
  – Separate sexes
  – Radiate from center at 5 points
  – Not perfectly radial
                                                                    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
                        Central disk. The central                                   Spine          covered by spines that help
                        disk has a nerve ring and                                                  defend against predators, as
                       nerve cords radiating from                                                  well as by small gills that
                            the ring into the arms.                                      Gills
                                                                                                   provide gas exchange.

                                                                                                     Madreporite. Water can flow
                                                                                                     in or out of the water vascular
                       Digestive glands secrete                                           Radial
                                                                                                     system into the surrounding
                       digestive juices and aid in                   Gonads               nerve
                                                        Ring                                         water through the madreporite.
                      the absorption and storage        canal              Ampulla
                                      of nutrients.                       Podium
               Radial canal. The water vascular                 Branching from each radial canal are hundreds of hollow, muscular tube
               system consists of a ring canal in the           feet filled with fluid. Each tube foot consists of a bulb-like ampulla and
               central disk and five radial canals,             suckered podium (foot portion). When the ampulla squeezes, it forces
               each running in a groove down the                water into the podium and makes it expand. The podium then
               entire length of an arm.                         contacts the substrate. When the muscles in the wall of the podium
Figure 33.39                                                    contract, they force water back into the ampulla, making the podium
                                                                shorten and bend.
   Echinoderms and Chordates
       are Deuterostomes
• Echinoderms continued
  – Divided into 6 classes
  1. Sea stars (asteroidea)
     • Multiple arms
     • Star shpaed
     • Regenerates
     • Turns stomach inside out to get prey
  2. Brittle stars (Ophiuroidea)
     • Figure 33.40b disk and long flexible arms
         Central (b) A brittle star (class Ophiuroidea)
     • No suckers on feet
Table 33.6
  Echinoderms and Chordates
      are Deuterostomes
• Echinoderms continued
  3. Sea urchins and sand dollars (Echinoidea)
    •   No arms
    •   5 rows of tube feet that help with slow movement
    •   Have muscles for locomotion
    •   Mouth has a ring-like jaw for seaweed
  Echinoderms and Chordates
      are Deuterostomes
• Echinoderms continued
  4. Sea Lilies and Feather Stars (Crinoidea)
    • Lilies – are attached to a substrate by a stalk
    • Feather – move with long flexible arms
    • Both use arms for suspension feeding
  5. Sea Cucumbers (Holothuroidea)
    • Lack spines, and their endoskeleton is much
    • 5 rows of (e) A sea cucumber (class Holothuroidea)
    Figure 33.40e tube feet
    • Have tentacles which are modified tube feet
  Echinoderms and Chordates
      are Deuterostomes
• Echinoderms continued
  – Sea daisies (Concentricycloidea)
    •   Disk shaped body with small spines
    •   Incomplete digestive system
    •   Live on submerged wood
    •   Armless body
    •   Discovered in 1986
    •   Two species are known

                      Figure 33.40f (f) A sea daisy (class Concentricycloidea)
• Phylum Chordata
• Consists of two subphyla of invertebrates as
  well as the hagfishes and the vertebrates
• Shares many features of embryonic
  development with echinoderms
• A summary of animal phyla

     Table 33.7

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