The Worm by bsw17644


									                The Worm

A Sophisticated Yet Small
    Characteristics of Worms
• Invertebrates
• Bilateral Symmetry
• Definite head where nerve and sense
  organs are concentrated
• Complex tissues: develops from 3 different
  tissue types including mesoderm (muscle)
          Habitats of Worms
1. Water: fresh and salty
  1. Aquatic worms swim
     1. Clam worms are predators
  2. Aquatic worms attach themselves
     permenantly to surfaces and build burrows
     1. Giant Tube Worms
2. Mud: worms burrow and crawl
3. Live hosts: parasitic worms
          Three Worm Phyla
1. Flatworms, Platyhelminthes
  – Flattened body shape, simplest worm
  – Developed organs and organ systems
  – Digestive cavity with one opening
  – Free living (planaria) or parasitic (flukes and
  – Hermaphroditic but cannot fertilize own eggs
         Parasitic Flatworms
• Flukes live in body tissues of animals
  making them sick
• Tapeworms live in intestines of animals
  – No digestive cavity! Absorbs nutrients directly
    from host.
  – Reproduction: pieces of worm break off and
    end up in host waste; if ingested by another
    animal, the eggs hatch in the new host
     • Don’t eat poop! WASH YOUR HANDS!
         Three Worm Phyla
2. Roundworms, Nematoda
  – Rounded body shape
  – Tiny, but visible to human eye
  – “tube within a tube”: 1-way digestive tract
    with a separate mouth and anus
  – Reproduction: sexual with separate male
    and female worms which produce 200,000
    eggs per day!
  – Free living and Parasitic worms
        Parasitic Roundworms
•   Hosts include plants, insects, animals,
•   Examples
    1. Hookworms: Enter sole of foot, bloodstream,
       lungs, and coughed into stomach
    2. Trichinella: Live in muscles of mammals
       (pigs); Eggs may infect humans if eat
       undercooked pork
      1. Trichinosis: flu-like symptoms, although rare,
         there is a risk to heart and nervous tissues
         Three Worm Phyla
3. Segmented Worms, Annelida
  – Body divided into small units or segments
  – Fluid-filled body cavity called a coelom
  – Coelom holds organs and supports them
    with “water skeleton”
  – Regeneration occurs in many species
  – Reproduction: Both male and female organs
    but require a mate; Secretes cocoon (egg
    case) with eggs and another worms’ sperm;
    Embryonic worms develop until emerging
    from cocoon as fully formed worms!
      Focus: Planaria Flatworms
•   Free living, freshwater worms; 2.5 cm long
•   Eyespots on top of head sense light/dark!
•   Food enters mouth (opposite end of head)
•   Sexual and asexual reproduction
    – Planaria can divide in half and regenerate two
      new worms!
• Nerve cells form simple brain in head…
    – Learning studies with planaria
Focus: Planaria
   Freshwater Planaria

                Land Planarian
 Focus: Earthworms (Annelida)
• Brain, nerve cord, and 5 hearts!
• Stiff bristles on segments aid movement
• Digestive organs: crop, gizzard, and
  – Grind up soil and remove organic material
  – Leave behind inorganics important to plants
    such as nitrates and phosphates (casts)
  – Aerate and mix soil, allow water to enter
  – Eats and discards it’s weight in soil each day
Focus: Earthworms
Focus: Giant Tube Worms
            •Phylum: Annelida
            •Habitat: Hydrothermal vents
            •Symbiosis with bacteria
            •Worm can retract into
            protective tube; Up to 8 feet
            •No mouth or digestive tract!
                                   Works Cited
•   Title image:
•   Land Planaria:
•   Planaria:
•   Planaria (green):
•   Planaria diagram:
•   Earthwrom:
•   Anatomy:
•   Tube worms:
•   Vents:

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