Invertebrates

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Invertebrates

• Chapter 33

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Invertebrates

• Invertebrates are animals without a backbone.
• The main phyla we will talk about are
• Porifera
• Cnidaria
• Platyhelminthes
• Nemotodes
• Mollusks
• Annelids
• Arthropods
• Echinodermata
• Some chordates

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Phylum Porifera

• Phylum Porifera are the sponges.
• They have radial symmetry.
• Resemble a sac filled with holes.
• They are non-motile filter feeders.
• Individual cells are specialized, but they have
  no true tissues.

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Phylum Cnidaria

• Cnidarians include hydras, jellyfish, sea
  anemones, and coral.
• They have radial symmetry.
• They have stinging threads.
• They can be polyps (stuck to the ocean floor), or
  medusa (floating jellyfish).
• Mouths lead to gastrovascular cavities where food
  is digested.

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Phylum Platyhelminthes

• Phylum Platyhelminthes are the flatworms,
  planarians, and flukes.
• They are the simplest animals with bilateral
  symmetry.
• Incomplete digestive tract.
• Flukes and tapeworms are parasitic flatworms.

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Phlyum Nemotoda

• Nemotodes are roundworms.
• They are the first pseudocoelomates and the first
  animals to evolve a complete digestive tract.
• They are used in research and found in
  undercooked pork.

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Phylum Mollusca

• Mollusca are the mollusks.
• They are the first animals with a true coelom, a
  circulatory system, and a nervous system.
• They have radulas which are used to scrape up
  food.
• Mollusks have a foot for locomotion, a mass where
  the organs are housed, and a mantle which
  protects them.

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Phylum Mollusca

• There are 3 types of mollusks
• Gastropods sea slugs, snails and slugs
• Bivalves clams, oysters, mussels, and scallops
  (2 hinged shells)
• Cephalopods built for speed and motility,
  include squid and octopi have sophisticated
  sense organs.

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Phylum Annelida

• Annelids include earthworms, Christmas tree
  worms, polychaetes (sand worms) and leeches.
• Annelids are the first animals to have segmented
  bodies.

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Phylum Arthropoda

• Arthropods include crayfish, lobsters, crabs,
  barnacles, scorpions, millipedes, centipedes,
  spiders, ticks, and insects.

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Phylum Arthropoda

• It is the largest phyla by number of animals.
• Arthropods have a hard exoskeleton, soft bodies,
  and jointed legs.
• Crustaceans like lobsters and crayfish are
  arthropods.
• Insects have 6 legs and a pair of wings and a
  body made of a head, thorax, and abdomen.

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Phylum Echinodermata

• Echinoderms are sea stars, sand dollars, and sea
  urchins.
• They have spiny skin and an endoskeleton.
• They have a water vascular system that is used
  for movement.
• They are radially symmetrical as adults, and
  bilateral as larvae.

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Phylum Chordata

• Chordates have 4 features
• 1. a dorsal, hollow nerve cord
• 2. a notochord (flexible rod between the
  digestive tract and the nerve cord)
• 3. Pharyngeal slits (gills)
• 4. Muscular post-anal tail

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Phylum Chordata

• Some chordates are actually invertebrates the
  tunicates and lancelets.
• Tunicates are stationary and look like small
  bags.
• Lancelets are small, bladelike animals that live
  in sand.