Porifera

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Lecture 2

• Porifera Cnidaria

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Phylum Porifera The sponges
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Evolutionary relationships

• Why or Porifera considered animals rather than
  Protists?
• How do they differ from other animals (3 ways)?

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(No Transcript)
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Sponge structure

• Review key parts
• No tissues, organs or body systems!

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Water movement and feeding choanocyte, Fig. 33.4

• Role of flagellum
• Role of collar
• Movement of particles
• Phagocytosis

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Amoebocytes

• Move in amoeboid fashion through mesohyle
• Secrete spicules and/or spongin
• finish digestion
• Garbage-collector cells
• Transport waste to excurrent pore
• Can develop into other cell types
• Somewhat like stem cells!

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Protection

• Sponges are sessile
• Toxins/warning coloration
• Painful or sharp covering (spicules)
• Regenerative ability
• Camouflage (if not toxic)
• Bore into shells.
• NOTE Nudibranch predators co-opt sponge
  defenses (toxins, spicules)

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Nudibranch (Phylum Mollusca, Class Gastropoda)
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Phylum Cnidaria
Scyphozoa
Anthozoa
Hydrozoa
Cubozoa
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Phylum Cnidaria
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Evolutionary relationships
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Radiata vs. Bilateria
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Body organization
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Key features

• Polyps and medusae
• Two germ tissue layers (called..?)
• Mesoglia
• Gastrovascular cavity (functions?)
• Nervous system nerve net
• Neurons? Brain? Nerve cords (bundles of axons)?
• Tentacles with cnidocytes (stinging cells)

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Cnidocytes/nematocystsHow do they work?
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Life-history strategies