1. Sponges

2. Jellyfish, Sea Anemones
Phylum Cnidaria
Jellyfish, Sea Anemones

3. Basic Info Soft-bodied animals with stinging tentacles
Live as singles, groups, and in connected colonies
Many different species (~9000)
All species have stinging cells called nematocysts

4. Habitat Most species live only in the sea
Found in all marine environments

5. Body Structure All have radial symmetry Polyp – sessile and flowerlike
Medusa – motile bell-shaped

6. Gastrovascular Cavity
Three cell layers: Epidermis, mesoglea, gastroderm
Gastroderm layer lines a central cavity called the gastrovascular cavity

7. Form and Function

8. Nematocysts – stinging cells located in tentacles
Shoots a poison dart into prey that paralyzes or kills it.
Tentacles – long extensions of the body help push food into the mouth

9. Body Systems Digestive:
Gastrovascular cavity – breaks down food into smaller, digestible pieces.
Mouth – entrance for food and exit for wastes
Gvc cavity branches in some cnidarians to transport food throughout the body.
Respiratory and Excretory:
Gastrovascular cavity filled with moving water for exchange of materials
Nervous:
Simple nerve net concentrated around the mouth

10. Organs Some medusae have simple organs called statocysts and ocelli
Statocysts are used for balance and orientation
Ocelli are “eye-spots” that detect light.

11. Movement No muscular system
Epidermal cells can change shape to cause movement
Medusae draw in water and expel it under high pressure to move – (jet propulsion)

12. Reproduction Most can reproduce sexually or asexually
Budding is common in polyps
Medusae often release gametes into the water where they can fertilize internally or externally

13. Class Hydrozoa Most common is a Hydra Interesting lifecycle
Mostly polyp form

14. Class Scyphozoa Jellyfish Life cycle similar to hydra
Can be up to 2 metres wide

15. Class Anthozoa Anemones and Corals Polyp throughout life cycle
Some sea anemones have photosynthetic symbionts

16. Importance Corals and anemones provide extensive habitats for fish
Medical research due to the toxicity of some of the chemicals they produce