1. Invertebrates
Sponges & Cnidarians

2. Sponges Kingdom: Animalia Simplest invertebrates
Phylum: Porifera (sponges)
Simplest invertebrates
Asymmetrical (no symmetry!)
No tissues, gut or nerves

3. How Do Sponges Eat? Filter feeders: feed on tiny plants and animals
Water carries food into the sponge through pores (ostia)
Ostia: holes on the outside of the body
Inside the sponge, collar cells remove food from the water
Collar cells: special cells that line the central cavity of the sponge; they digest food
The water exits through an osculum
Osculum: hole at the top of the sponge

4. Sponge Anatomy Where does the water enter? Where does the water exit?
What structure on the collar cells pushes the water up?

5. Body Part Abilities
If a part of a sponge is broken off, the missing part can regenerate, or grow back
If a sponge is broken into pieces, new sponges could form from each piece
If you force a sponge body through a strainer, the separated cells could come back together and reform the same sponge!

6. Kinds of Sponges All live in the water (most in salt water)
Come in different shapes/sizes
Most sponges have a skeleton made of hard fibers called spicules
Grouped by their type of skeleton
Barrel sponge
Tube Sponge
Finger Sponge
Vase Sponge

7. Cnidarians Pronounced “nigh-dare-e-ins” Kingdom: Animalia
Phylum: Cnidaria
Invertebrates that have stinging cells
More complex than sponges
Have complex tissues, a gut & simple nerves
Include: jellyfish, hydrozoa, sea anemones and coral

8. Two Body Forms Cnidarians have ONE of the two body forms:
Medusa: swim through the water
Polyp: attach to a surface
Some change forms at different times in their life

9. Special Cells
All cnidarians have tentacles covered with stinging cells
Nematocysts: stinging cells that release spears into an organism when it brushes the tentacles
Some can release poison
Used for protection and to catch food

10. Kinds of Cnidarians **We split them into four classes:
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Scyphozoa
Anthozoa
Cubozoa

11. Hydrozoans Hydra, Portuguese Man-o’War
Hydra are always polyps (attached)
Live in fresh and salt water
Many live in colonies

12. Scyphozoans Jellyfish Catch other inverts and fish in tentacles
Spend most of their life as a medusa

13. Anthozoans Sea Anemones and Corals Spend their lives as polyps
Often brightly colored
Live in colonies

14. Cubozoans Are square shaped when viewed from above
Resemble true jellyfish
Have well developed eyes
Are one of the most deadliest animals in the ocean