1. Phylum Cnidaria

2. Phylum Cnidaria – “stinging cell”
A.k.a Coelenterata (hollow cavity)
Radiata (radial symmetry)

3. Jelly Fishes

4. Sea Anemones

5. Corals

6. One step above sponges…
Differ from sponges - have rudimentary organs
Incomplete digestive & excretory systems
No blood or circulatory system

7. Classification 3 Classes Hydrozoa = Hydra Scyphozoa = Jellyfish
Anthozoa = Sea anemones & coral

8. Morphology Body wall - 3 layers Epidermis (outside)
Mesoglea (inner transluscent jelly-like material)
Gastrodermis (inside lining)

9. Skeletal Structure
Corals secrete calcium carbonate to build exoskeleton
Most sea anemones and hydra use water pressure from inside body cavity (hydrostatic pressure) to maintain body form

10. Body Features Mouth usually surrounded by tentacles (radial symmetry)
Tentacles covered in cnidocytes = specialized stinging cells
Nematocysts = Shoots like a harpoon from cnidocyte. Contains deadly toxin.
Gastrovascular cavity – Hollow digestive cavity
Mouth serves as entrance/exit point

11. Nervous System
No brain
Nerve net
Capable of responding
to stimuli

12. Habitat Aquatic, mostly marine
Hydra – Freshwater, independent, free swimming
Jellyfish – Marine, independent, free swimming
Coral & Anemone – Marine, sessile, colonial

13. Body Forms Polyp – present in all 3 classes Hollow tube with tentacles
Can be free swimming (hydrozoa, scyphozoa) or sessile (anthozoa)

14. Body Forms Medusa – only present in hydrozoa and scyphozoa
Free swimming
Umbrella shaped with tentacles
Mesoglea constitutes bulk

15. Reproduction Hydrozoa & Scyphozoa – Anthozoa –
Asexual reproduction in polyp form by budding
Sexual reproduction in medusa form
Anthozoa –
No medusa form, but can reproduce asexually (budding) or sexually

16. Close-up of
Hydrozaon polyp

17. Hydrozoan medusa