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Characteristics of Simple Worms


Characteristics of Simple Worms Phylum Platyhelminthes is made up of flat worms. They have a flattened tube of muscle, simple digestive system, a single opening that ... – PowerPoint PPT presentation

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Title: Characteristics of Simple Worms

Characteristics of Simple Worms
  • Phylum Platyhelminthes is made up of flat worms.
  • They have a flattened tube of muscle, simple
    digestive system, a single opening that serves as
    both mouth and anus.
  • Phylum Nemertea are more complex with a flat
  • They have a simple blood vascular system, one-way
    digestive system, separate mouth, and anus.
  • They are carnivores.

  • Phylum Nematoda are structurally simple round
  • More complex than the other two phyla. Most are
    parasitic worms, some live in sea animals.
  • This phylum also includes human parasite forms.
  • Special Attributes of Simple Worms
  • Lineus longissimus, a nemertean, found in
    the North Sea is perhaps the longest known
    creature in the world more than 60 meters (197

Features of segmented worms
  • Members of the Phylum Annelida (which means
    little rings)
  • Most are in the class Polychata
  • 6000 species of polychata
  • Tube-shaped body divided into segments (which is
    where the name comes from)
  • Found
  • Fresh water
  • Salt water
  • Moist soil

  • They have a body cavity which holds their organs
  • Closed circulatory system
  • Crawling worms (2- 4 inches) are carnivores
  • Those that burrow are deposit feeders
  • They all have Setae
  • Bristle-like structures on the sides of each
  • Helps worms move through the soil and hold on to
    the soil
  • Some have developed gills on these

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  • The planktonic larval phase is called a
  • Band of cilia around the body
  • Some species can reproduce asexually by fission.
    Earthworms do NOT reproduce asexually. They
    reproduce sexually. They are hermaphroditic.
    Other annelids are either male or female.
  • Most live in tubes made of mucus, seaweed,
    cemented mud, etc

Characteristics of Annelids
  • Worms in phylum Annelida stand apart because of
    their structural complexity.
  • They have a heart, nephridia, and sometimes,
  • Most important, they exhibit metamerism the
    division of the body into repeating blocks or
  • Special Attributes of Annelids
  • Of particular relevance to oceanography class
    Polychaeta, because many polychaete worms live
    in the marine environment.
  • 1. Tubeworms have flower-like antennae.
  • 2. Bristleworms sting when touched.
  • 3. Spongeworms live on sponges.
  • 4. Fireworms live on the surface of fire coral.

Other types
  1. Oligochaetes class Hirudinea. They are
    earthworm relatives
  2. Leeches most are freshwater, those that are
    marine water typically live on another fish.
    They have no parapodia
  3. Sipunculans unsegmented bodies and bury
    themselves in mud. Exclusively marine and in
    shallow waters

  1. Echiurans over 100 species and are exclusively
  2. Pogonophora lack a digestive system (including
    mouth and gut). Also known as beard worms
  3. Chaetognaths one of the smallest animal phyla.
    They have eyes, teeth, grasping spines,
    transparent and fish like fins and tails

Characteristics of Mollusks
  • Phylum Mollusca the mollusks ranges from
    squid and octopuses to sea slugs, snails,
    oysters, clams, and conches.
  • It has the most species of any other ocean group
  • Making it the most successful at 110,00 species
  • Immense diversity in structure and habitat
  • Can be found in splash zones of rocky shores to
    deep sea hydrothermal vents
  • Can thrive on just about every concievable diet

  • Three characteristics all members share
  • A muscular bag called the mantle.
  • A thin layer of tissue that covers the body
  • Produces the shell
  • Shell is made of CaCO3 to protect its soft body
  • A muscular foot beneath the head (ventral).
  • Used for locomotion
  • Most have a head with eyes, sensory organs, and a
    radula (a tongue with rough scraping teeth used
    for feeding).
  • Radula is made of Chitin
  • A highly resistant material found in many
  • Bodies are unsegmented, Bilaterally symmetrical

All mullusks have the same basic body plan with
some modifications
  • Shell is internal in squids and absent in sea
    slugs and octopuses
  • Portions of the body are coiled and asymmetrical
    in snails
  • The radula is modified or absent in some mollusks

  • Special Attributes of Class Gastropoda
  • Snails, whelks, slugs, and most single-shelled
    mollusks belong in class Gastropoda.
  • 75,000 species, mostly marine
  • Basically a coiled mass of vital organs enclosed
    by a dorsal shell
  • Shell is usually coiled and rests of the on a
    ventral creeping foot

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Varied types of feeding
  • Use radula to scrape algae from rocks
  • Periwinkles, limpets, abalone
  • Deposit feeders feed off of soft bottoms
  • Mud snail
  • Carnivores
  • Whelks, oyster drills, cone shells
  • They specialize in prey like clams, oysters,
    worms, and even small fish
  • Violet snails prey on siphonophores
  • Sea slugs (nudi-branch) feed off of sponges and
  • They use noxious chemicals and nematocysts

  • Torsion is a developmental process.
  • It occurs after the veliger settles and begins
    maturing. Its body twists into a permanent loop
    that rearranges the organs and brings them
    together allowing the body to draw into the
    spiral shell common to this class.

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Class Bivalvia
  • Belonging to class Bivalvia (bi meaning two) are
    mollusks that have two hinged shells.
  • Mussels, clams, oysters, and scallops are all
  • Has the basic Mollusk structure
  • Body is laterally compressed and enclosed in 2
    valved shells
  • No head nor radula
  • Gills used for breathing Oxygen and sorting small
    food particles
  • Inner surface lined by a mantle
  • body lies in mantle cavity

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  • Use a shovel-shaped foot to burrow in sand and
  • Forms siphons by fusing edge of mantle to draw in
    and out water to allow clams to feed and obtain
    oxygen while buried in sediment

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  • Do not burrow
  • Instead attaches to rocks and other surfaces
    using byssal threads

  • Cement shell to hard surfaces
  • Often another oyster
  • Pearls form when oysters secretes CaCO3 to coat
    an irritant
  • Can be particles of sand to parasites lodged
    between the mantle and the iridescent
  • Cultured pearls are obtained by carefully
    inserting bits of shell or plastice

  • Some scallops live unattached and swim for short
    distance by rapidly ejecting water from mantle
    cavity and clapping valves
  • Giant clam is the largest bivalve at over 1 meter
  • Fouling organism is a common problem for ocean
  • Some bivalves attach to wood such as on boats

Class Cephalopoda
  • They are all predators that specialize in
  • Very agile swimmers, displaying a complex nervous
  • They have a reduced or eliminated shell
  • The basic structure is a head pushed down toward
    a foot that has been modified as arms equipped
    with suckers to capture prey

  • They have eyes that are similar to ours in
  • Bodies are protected by a thick muscular mantle
  • Elongated in squid, rounded in octopuses
  • Mantle forms a mantle cavity enclosing 2 or 4
  • They have a structure called a Funnel
  • Muscular tube formed by what remains of the foot
    used as siphon (an exit for water that enters
    through a free edge of the mantle
  • Used for swimming by forcing water out
  • Funnel is flexible allowing it to be relocated

  • This class includes cuttlefish, squid and
  • Cuttlefish (order Sepioidea) differ from squid
    and octopuses by having an internal shell used
    primarily for buoyancy.
  • Squid (order Teuthoidea) differ from cuttlefish
    and octopuses with their streamlined,
    torpedo-shaped bodies adapted to life in open
  • Octopuses (order Octopoda) differ from squid and
    cuttlefish by having no shell and living in rocky
    reefs and coral.
  • Octopuses are probably the most intelligent

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Biology of Mollusks
  • Digestion
  • Contain a separate anus and mouth
  • Digestion involves digestive glands such as
    salivary glands that release enzymes which break
    down food into simpler molecules
  • Circulatory system transports nutrients and
    oxygen to cells using a dorsal, muscular heart
  • Most mollusk have an open circulatory system
  • All cephalopods have a closed system

Differences in digestion
  • Chitons and snails use a combination of
    extracellular and intracellular digestion
  • Snails keep chloroplast intact and continue to
    carry put photosynthesis
  • Carnivorous snails modify radula to drill and
    capture prey. May even have jaws.
  • All extracellular
  • Bivalves have long strings of mucus in mouth to
    trap food

  • Crystalline style in stomach rotates food to help
  • Contents eventually pass into large digestive
    gland for intracellular digestion
  • Giant clams contain zooxanthellae that live in
    tiny branches of gut that extend into mantle for
    extra nutrients
  • Cephalopods are entirely extracellular. Stomach
    is connected to an extra sac to speed up digestion

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Nervous System and Behavior
  • Snails, chiton, and bivalves possess a ganglia
  • Cephalopods have a true brain.
  • Design of their brain is similar to humans
  • Like humans, body is controlled through a
    combination of nerve fibers and the brain
  • High learning capacity
  • Can control color change depending on mood

Reproduction and Life History
  • Some are hermaphrodites
  • Bivalves, chitons, and some snails fertilize
  • Cephalopods and most snails are internal
  • Males modify an arm to transfer a spermatophore
  • Snails use a long, flexible penis
  • Female octopuses protect the eggs until hatched
  • Young develop in yolk-filled egg
  • Female usually dies after eggs hatch

  • Phylum Arthropoda is the most numerous of
    multicellular animal phyla.
  • There are several intermediate classifications.
  • There may be as many as one million arthropod
  • 3 out every 4 animals is an arthropod
  • Characteristics segmented bodies, jointed legs,
    a chitinous exoskeleton.
  • Segmented bodies with bilateral symmetry
  • Segmentation adds flexibility
  • Jointed appendages
  • Including the mouth
  • Moved by sets of attached muscles
  • They have a chitinous exoskeleton
  • Secreted by underlying layer of tissue
  • Tough, non-living material

  • In order to grow, arthropods must shed their
    rigid shells
  • Process is known as molting
  • Animal takes in water to expand and forms a new
  • Exoskeleton limits size and growth
  • Will never be a giant but exoskeleton and joints
    gives a successful combination of protection,
    support, flexibility, and increase surface area
    for muscle attachments

Superclass Crustacea
  • an intermediate classification.
  • Characteristics include
  • A pair of appendages on each body segment.
  • Specialized for swimming
  • Two pairs of antennae.
  • Mandibles for chewing.
  • Teardrop-shaped larvae.
  • Exoskeletons are shed as they grow.

Special Attributes Krill
  • Class Malacostraca includes two orders of
    interest due to their roles as food for humans
    and food for nature.
  • Order Euphausiacea krill
  • Krill are important primary and secondary
    consumers that link smaller plankton to larger
  • In subpolar food webs, they are vital. Whales,
    seals, sea birds, and penguins only survive in
    highly productive waters. Much of the food web
    above krill depends on it for life.

  • 10 legs
  • 1st pair usually has claws to obtain food and
  • Referred to as cheliped
  • Rest of body is divided into the Cephalothorax
    and abdomen
  • Have claws and an extended carapace that encloses
    the gills.
  • Because humans eat these shellfish, they are an
    important food source and resource on which the
    fishing industry relies.
  • Includes shrimp, lobster, crabs, hermit crabs
  • Hermit crabs are not actual crabs
  • Shrimps have laterally compressed bodies and
    elongated abdomen like a lobster
  • Also scavengers
  • Crabs have a broad cephalothorax and a tucked in

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Special Attributes of Class Cirripedia
  • Barnacles unique lifestyle sets them apart into
    class Cirripedia.
  • Life begins as free-swimming larvae like other
  • When the larva finds a surface on which to live
    (rocks, boats, etc.) it fuses itself in place
    upside down.
  • The exoskeleton forms the carapace (hard shell)
    the barnacle can withdraw into for protection.

Special Attributes of Copepods
  • Copepods play a central role in the ocean food
  • They are important primary and secondary
    consumers of phytoplankton and zooplankton.
  • Relatively few larger animals can consume the
    tiniest plankton, but many can eat the larger
    copepods. Fish, krill, and giant
    plankton feeders, including whale sharks, baleen
    whales, and manta rays all eat copepods.
  • Copepods are important to ocean food webs because
    they link the tiny primary producers and
    consumers to the large animals higher up the web.

  • Filter feeder
  • Stiff, hair like fibers to catch food
  • Particles carried by currents caused by other
    moving appendages
  • Parasitic crustaceans have bristles used for
    piercing and sucking
  • Maxillipeds are the appendages closest to the
    mouth are turned upward and specialized to sort
    out food and push it in to the mouth
  • 3 pairs
  • Stomach has chitinous teeth/ridges for grinding
    and bristles for sifting

Nervous system and Behaviour
  • Small, simple brains that are more centralized in
  • Highly developed sensory organs
  • They have compound eyes
  • In decapods eyes act as periscope
  • Keen sense of smell
  • Use a pair of statocysts for balance
  • Use signals to communicate with each other

  • Generally have 2 genders
  • Gametes are rarely shed into water
  • Males have a specialized appendages to transfer
  • Even hermaphroditic species
  • Usually occurs immediately after female decapods
  • Can store sperm for long periods of time
  • Nauplius is a common crustacean larva

Characteristics of Echinoderms
  • Even though the organisms in phylum Echinodermata
    dont at first look and act much like animals,
    they are.
  • They move. They attack prey. They defend
    themselves. They just tend to do so very slowly.
  • They all share
  • A radially symmetrical body divided into five
  • Most have hundreds of tiny tube feet to crawl and
  • Most have a water vascular system that brings
    oxygen to the body cells.
  • Echinoderms have some traits close to chordates.
  • The adult is radially symmetrical.
  • The larvae are bilaterally symmetrical.
    Bilateral symmetry, along a vertical axis, is
    what mammals, fish, etc. have.

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Special Attributes of Crinoids
  • Class Crinoidea include feather stars and sea
  • The primary characteristics of this
  • class are
  • Long feather-like arms and short, hook-like legs
    called cirri.
  • They have upward-facing mouths.
  • Most are nocturnal feeders. At night, they
    unfurl their arms to capture plankton and
    nutrients carried into their paths by the
  • By day they coil up tightly and hide in the reef.
  • Most crinoids attach to the bottom by their cirri.

Special Attributes of Sea Stars
  • Sea stars belong to class Asteroidea.
  • They are predators with downward-facing mouths.
  • They have tube feet covering their undersides.
  • They usually have five arms.
  • A few species have toxic spines for protection.
  • Each arm carries an equal share of the animals
    systems and organs.
  • They can regenerate a lost limb, some grow into
    several new animals when cut into pieces.

Special Attributes of Brittle Stars
  • Brittle stars belong to class Ophiuroidea.
  • This class has slender legs that are
    proportionately longer and thinner than those on
    sea stars.
  • Brittle stars feed on detritus and small animals.
  • They use arms and tube feet for locomotion.

Special Attributes of Sand Dollars and Sea Urchins
  • Sand dollars and sea urchins are part of class
  • They have the five-section body, but no arms.
  • Sand dollars and sea urchins share a disk-shaped
  • They have tube feet on the underside.
  • Sea urchins graze on algae.
  • Swimmers avoid sea urchins because of their
  • Some species have toxins in the spines for
  • Urchins can move their spines to assist in

Special Attributes of Sea Cucumbers
  • Sea cucumbers are part of class Holothuroidea.
  • They have an elongated five-segment body with
    tentacles around the mouth.
  • Most feed by moving with their mouths open,
    allowing sand to flow through. A few are filter
  • Some expel a sticky mass of white tubes covered
    in toxin.
  • They are protected by tough skins and by the
    ability to expel part of their internal organs
    for predators while saving the rest to survive.

  • Carnivorous
  • They invert stomach through the mouth to envelope
  • The intestine is short or missing
  • The body cavity is filled with a coelomic fluid
  • Also serves to bring in oxygen.
  • Sea cucumbers bring in water through the anus to
    the respiratory branches
  • Extensions of gut

  • They have separate sexes with 5, 10, or more
    gonads that shed sperm or eggs
  • Spawning
  • Gametes do not survive long in the water
  • Individual spawn all at once
  • Fertilized egg develop into the plankton and
    results in a ciliated larva
  • Some echinoderms carry eggs

  • Asexual reproduction
  • Fission
  • The central disk splits into 2 new individuals
  • Regeneration
  • The ability to grow missing parts
  • Requires that part of the central disk be present
    to grow a new individual
  • Sea star do not require the disk