1. PHYLUM CNIDARIA (Sea Anemones, Jellyfish, Coral, Hydras)
~ species
FACT: Cnidarians have a single external opening that serves as both
the mouth and the anus!

2. CNIDARIA Cnidae refers to the creatures’ “stinging cells”
Are further up the “evolution ladder”
meaning they are more complex than Porifera (sponges)
Three Classes
Class Hydrozoa
Class Scyphozoa
Class Anthozoa

3. CNIDARIA MULTICELLULAR
cells are specialized and organized into tissues and sometimes even into simple organs
all Cnidarian have specialized defense cells that sting = cnidocytes
cnidocytes (the cell) contain a unique organelle = called nematocyst = “stinger”
GERM LAYERS
Only endoderm and ectoderm
Endoderm – forms inner gastrodermis
Ectoderm – forms outer epidermis

4. CNIDARIA MOVEMENT medusa form (bell-shaped) is motile (moving)
polyp form (vase-shaped) is sessile (non-moving)
some cnidarians exist in both forms throughout their life cycle (alteration of generations)
medusa polyp
(motile) (sessile)

5. CNIDARIA Two body forms Polyp Medusa Tubular shape Mouth faces upwards
Sessile
Medusa
Mouth faces downwards
Motile (drifters)

6. CNIDARIA REPRODUCTION Asexual – budding
Sexual – monoecious, produce both sperm and eggs
Sexual – male (produce sperm)
- female (produce eggs)

7. CNIDARIA no body cavity because no true mesoderm radial symmetry
non-segmented
have tissues
gastrodermis (gas exchange and digestion)
epidermis (protection)
middle layer = mesoglea (jelly-like)
have a “nerve net”

8. CNIDARIA
DETAILED STRUCTURE (Example of Hydra)

9. CNIDARIA
BODY SYSTEMS
REPRODUCTIVE SYSTEM – a rudimentary system in some organisms
Asexual Reproduction
budding (no system)
Sexual Reproduction
Monoecious = individuals produce both sperm (testis) and eggs (ovary)
Dioecious = male produce sperm (testis) and females produce eggs (ovary)

10. CNIDARIA BODY SYSTEMS REPRODUCTIVE SYSTEM and LIFE CYCLES
Alternation of generations
Aurelia (jelly fish) Obelia (hydra)

11. CNIDARIA BODY SYSTEMS DIGESTIVE SYSTEM – not a true system
food enters gastrovascular cavity via mouth
extracellular digestion (enzymes secreted into cavity)
cells lining the cavity absorb digested nutrient and smaller food particles

12. CNIDARIA BODY SYSTEMS CIRCULATORY SYSTEM – not a true system
nutrients and gasses diffuse directly across the thin cell layers
RESPIRATORY SYSTEM – not a true system
gas exchange directly between cells and water by diffusion (O2 diffuses into and CO2 out of cells)
Both across epidermis and gastrovascular tissues

13. CNIDARIA BODY SYSTEMS EXCRETORY SYSTEM – not a true system
waste diffuses from cells into gastrovascular cavity
waste is then released through the mouth
MUSCULAR SYSTEM – NONE
no muscle cells but some cells can contract and relax (e.g. in the tentacles)
SKELETAL SYSTEM – NONE

14. CNIDARIA BODY SYSTEMS Nervous System – a basic system
a net of nerve cells
react to presence of food and danger
for feeding and protection
Hydra Feeding

15. CNIDARIA GENERAL INFORMATION HABITAT
mostly marine waters (marine = salt water)
some freshwater species
SIZE
as small as 0.5 cm tall
bell of up to 2.4 m diameter and tentacle ranging upwards of 50 meters

16. CNIDARIA - Class Hydrozoa
colonial organisms
hydras, Portuguese Man-of-War
medusa and polyp forms

17. CNIDARIA - Class Scyphozoa
“Cup Animals”
jelly fish
predominantly in the medusa form

18. CNIDARIA - Class Anthozoa
“Flowering Animals”
sea anemones
coral
predominantly in the polyp form
sea anemone coral
and clown fish

19. http://www.youtube.com/watch?v=pYUZxS1bZR4 = Steve Irwin and Box Jelly