Porifera, Ctenophora, Cnidaria

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  • Porifera, Ctenophora & Cnidaria
    • Porifera 'pore-bearer'
      • 9,000-15,000 species - 50 in freshwater, others marine
      • Polar to tropics - most prefer clear, quiet water
      • Sessile
      • Low-energy
      • Filter feeders
      • Loosely organised - no symmetry, muscles or nervous system
      • Body plan = aggregation of cells built around water canal system - chimney-like
      • Water currents: enter through ostia, leave via osculum at top
      • Few types of cells including choanocytes ('funnel cell')
      • Jelly-like extracellular matrix
      • Sexual reproduction
        • Sperm sent out via osculum
        • Ciliated larvae, often free swimming
          • Settle and develop into juveniles
        • Asexual reproduction by budding
      • 3 classes: demospongia hexactinella calcarea
    • Ctenophora 'comb carriers'
      • Comb jellies
      • 2 cell layers separated by gelatinous mesoglea
      • Common in open sea
      • ~150 species
      • Complete through-gut
      • Ctenes - cells with plates of cilia which move animal
    • Cnidaria
      • Genera to remember: Actinia, Aurelia & Hydra
      • ~11,000 species
        • All aquatic
        • Almost all marine
      • Diploblastic - 2 cell layers separated by mesogloea
      • Muscle fibres and nerve nets
      • Cnidocytes ('stinging cells') - catch prey with little energy
      • LIFE CYCLE
        • Sessile polyp
          • Asexual
          • Individual polyps may bud to form colonies
        • Motile medusae
          • Shed eggs and sperm into water
      • Sometimes called coelenterates
      • 4 EXTANT CLASSES
        • Anthozoa ('flower animals')
          • Sea anemones, hard corals, soft corals
          • All marine
          • Lack medusa stage
        • Hydrozoa ('water animals')
          • Diverse life cycles
          • Polyp commonly dominates life cycle
          • Most are colonial
        • Scyphozoa (jellyfish)
          • 'Cup-shaped'
          • All marine
          • Medusa often large
          • Polyps small and in-conspicuous
        • Cubozoa (box jellyfish)
          • Square bell rather than round
          • Eyes with a retina, lens, iris and visual behaviour
          • Some extremely venemous

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