Animals - Protostomes

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Animals - Protostomes

• Chapter 29

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Characteristics of Protostomia

• Based on embryonic development
• Spiral cell arrangement early cell divisions
  are diagonal to the polar axis
• Determinate cleavage each cells fate is fixed
  very early
• Blastophore develops into the mouth

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Platyhelminthes Flatworms

• The largest group of acoelomate worms
• Contain a mesoderm
• Have tissues organized into organs
• Bilaterally symmetrical
• Flat, ribbon-like body
• Have a highly branched gastrovascular cavity
• Dissolved substances move through the body by
  diffusion
• Most do not have a respiratory or circulatory
  system

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Planaria
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Marine Flatworm
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Tapeworm
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Fluke
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Nematodes Roundworms

• Pseudocoelomates fluid movement acts as a
  simple circulatory system
• Have a one-way digestive tract

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Ascaris
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Trichinella
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Hookworms
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Mollusks Soft-bodied Animals

• Snails, slugs, oysters, clams, scallops,
  octopuses, squid
• A larval stage called a trochophore
• Second largest phylum of animals
• Found in almost all marine, freshwater and land
  ecosystems
• Three major classes
• Gastropods
• Bivalves
• Cephalopods

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Gastropod means stomach-foot
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Bivalve means two-shells
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Cephalopods head-foot squid, chambered
nautilus, octopus
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Annelids Segmented Worms

• Coelomates
• 2/3rds are marine
• Each segment contains digestive, excretory,
  circulatory and locomotor organs and is separated
  from other segments by septa
• Some segments also contain areas responsible for
  specific functions such as reproduction, feeding
  or sensation
• A primitive brain the cerebral ganglion is
  located at the anterior end, with a nerve cord
  that runs the length of the body

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Marine Tube Worms glue grains of sand together to
make their tubes
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Marine Feather Duster Tube Worms
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Earthworms are hermaphrodites but dont fertilize
their own eggs
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Leeches can be useful medicinally
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Arthropods jointed legged animals

• All have jointed appendages legs, antennae, and
  mouth parts
• The largest group of animals more arthropods
  than all other groups combined
• Divided into two groups those with jaws and
  those with fangs or pincers

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Three body parts head, thorax, abdomen
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Cephalothorax combines head and thorax with a
separate abdomen
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Arthropods must molt their exoskeletons as they
grow
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Spider fangs
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Some arachnids have pincers
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Centipedes 1 pair of legs/segment
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Millipedes 2 pairs of legs/segment
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Isopod
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Shrimp
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Lobster
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Crabs
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Crayfish
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Barnacles