Download Phylum Cnidaria

*Refer to Chapter 6 in your Textbook
Learning Goals:
1. I can label the anatomy of a cnidarian.
2. I can describe the life cycle of a cnidarian.
3. I can differentiate between the different classes of
cnidarians.
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
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
Cnidarian Structures:
 Tentacles:
 feeding and locomotion
 Nematocysts:
 Coiled stinging dart ready to strike
located on tentacles
 Cnidocytes:
 Stinging cells located
within the dart
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
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
Cnidarian Classes:
 Class Schyphyzoa “True Jellies”
 Medusa is the predominant stage
 Carnivorous Predator
 Class Cubozoa “Box Jellies”
 Most venomous jellyfish in the
world
 Carnivorous Predator
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
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