1. Lesson 10.2: Cnidarians (Jellies & Corals)
*Refer to Chapter 6 in your Textbook

2. Learning Goals: I can label the anatomy of a cnidarian.
I can describe the life cycle of a cnidarian.
I can differentiate between the different classes of cnidarians.

3. Cnidarian Characteristics:
Tissues, but still no organs
Radial Symmetry:
have a central axis (like a pizza)
Two Body Plans:
Polyp: sessile stage
Medusa: free-floating stage

4. Cnidarian Structures:
Tissues:
Ectoderm (or Epidermis): outer most layer of cells
Mesoglea: gelatinous material making up majority of the animal’s body
Endoderm: lining of the inside of the body
Gastrovascular cavity: (pre-stomach)
where digestion occurs
Mouth/Anus:
food enters and waste is removed

5. Cnidarian Structures:
Tentacles:
feeding and locomotion
Nematocysts:
Coiled stinging dart ready to strike
located on tentacles
Cnidocytes:
Stinging cells located
within the dart

7. Cnidarian Life Cycle: Both asexual and sexual in same cycle Asexual:
From polyp to medusa
Sexual:
From medusa to polyp
*Draw the diagram on
the board

8. Cnidarian Classes: Class Hydrozoa:
Colony = individual members physically connected and adapted to share resources
Ex. Portuguese Man of War
Individual polyps have different roles:
Feeding - Carnivorous Predator
Reproduction
Defense

9. Cnidarian Classes: Class Schyphyzoa “True Jellies”
Medusa is the predominant stage
Carnivorous Predator
Class Cubozoa “Box Jellies”
Most venomous jellyfish in the
world

10. Cnidarian Classes: Class Anthozoa “Flower animal”
Sea anemones and corals
No medusa stage, Sessile
Corals secrete a hard skeleton
Suspension feeding:
grab plankton from the water
while sessile

11. Cnidarian Ecological Roles:
Symbiotic Relationships:
Zooxanthellae with Coral
Clownfish with Anemone
Habitat:
Coral reefs are the most diverse
ecosystem on Earth
Human:
Tourism
Pets
Medicine