1. Cnidaria
    • metazoan: have true tissue but lack organs
    • radial symmetry
    • 2 germ layers (endoderm and ectoderm)
    • acoelomate: lack body cavity
  2. Cnidocytes
    contain nemtocysts - stinging organelles
  3. Nematocysts
    • stinging organelles in Cnidarians
    • when stimulated, ejact small harpoon-like projection w/ toxins
    • involved in anchoring, feeding, or defense
  4. Anthozoa
    coral and sea anemones
  5. Hydrozoa
    hydras and some corals
  6. Cubozoa
    box jellyfish and sea wasp
  7. Scyphozoa
    jellyfish and sea nettles
  8. Cnidarian Body Plan (2)
    • sessile polyp: attached to surface
    • medusa: free-swimming
    • in both forms, ring of tentacles surrounds mouth to capture food/protect organism
  9. GVC
    • Gastrovascular Cavity
    • allows for ingestion of "food" much larger than individual cells
    • helps distribute food in preliminary phases of digestion
    • lined with gastrodermis
  10. Gastrodermis
    • has gland cells that secrete digestive enzymes => proteases
    • aids in digestion
  11. Proteases
    • secreted by glands in gastrodermis
    • hydrolyzes peptide bonds
  12. Pseudopods
    • engulf partially digested material
    • stores food in food vacuoles where final digestion occurs
    • formed from nutritive-muscular cells
  13. Nutritive-Muscular cells
    • contain flagella that beat and move fluid within gastrovascular cavity
    • form pseudopods
  14. Cnidarian Body Wall
    • two cellular layers:
    • outer epidermis: dervied from ectoderm
    • inner gastrodermis: derived from endoderm
    • mesoglea: space inbetween these layers
  15. Mesoglea
    • spaced between outer epidermis and inner gastrodermis
    • filled with extracellular matrix
    • thick and "jelly-like"
    • fuctions like endoskeleton -> provides support and attachment point for muscle cells
  16. Cnidarian Nervous system
    • primative/ in form of an irregular net that allows animal to respond to stimuli in a coordinated fashion
    • limited sensory capabilities
    • no sign of cephalization = central nervous system
  17. Hydra
    • freshwater
    • lacks medusa stage
  18. Hydra Body
  19. Hydra Basal Disk
    where it attaches to surface
  20. Hydra Reproduction
    • both asexual and sexual (with gametes
    • produce young asexually by mitotic cell division
    • some dioecious: male and female repro organs
  21. Cnidarian: Symmetry
    radial with oral and aboral surface
  22. Cnidarian: other body plans
    medusa and polyp
  23. Cnidarian: # Germ layers
    • 2 (development of tissues, no organs)
    • ectoderm -> epidermis
    • endoderm -> gastrodermis
  24. Cnidarian: Metamerism
    segmentation: none
  25. Cnidaria: Coelom
  26. Cnidaria: Skeletal System
    • none in hydrazoa
    • CaCO3 in coral (anthrozoa)
    • mesoglea: space btwn epidermis and gastrodermia that functions like endoskeleton but is NOT a true cellular layer
  27. Cnidaria: Cephalization
    central nervous system: none
  28. Cnidaria: Nervous System
    • primative
    • irregular net
    • respond to stimuli in coordinated fashion (i.e. outer tentacles engulf while inner contracts)
    • limited sensory capabilities
  29. Cnidaria: Digestive System
    • Gastrovascular cavity
    • tentacles used to gather food
    • gastrodermis lines cavity -> glands that secrete protease
    • nutritive muscular cells form pseudopods -> engulf partially digested food and transport them to final digestion site
  30. Cnidaria: Circulatory System
    • none (Diffusion)
    • cilia surrounding cavity moves fluid and food
  31. Cnidaria: Respiratory System
    none (Diffusion)
  32. Cnidaria: Excretory System
    none (Diffusion)
  33. Cnidaria: Sexual Cycle
    • monoecious or dioecious
    • hydras can be either dioecious or hermaphroditic
  34. Cnidaria: Locomotion
    • Tumbling, swimming, floating, gliding
    • tentacles and body contract and release for swimming in medusa stage
    • in polyp stage, nematocysts help attach it to surface
  35. Cnidaria: Notes
    • cnidocytes with nematocysts
    • 10,000 species, mostly marine
    • hydras are freshwater and have no medusa stage
    • evolved 580 mya
  36. Cnidaria: Classes
    • anthrozoa: coral and amemone
    • hydrozoa: hydras, obella/obelia
    • cubozoa: box jellyfish, sea wasps
    • scyphozoa: jellyfish, sea nettles
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