1. Cnidarians
Sandra Benito J.H., 9B

2. Facts

3. Before: Coelenterata phylum, meaning "hollow guts."
Name: Cnidarians
Before: Coelenterata phylum, meaning "hollow guts."
Included certain ctenophores and sponges.
From the Greek "cnidos," meaning "stinging nettle.“
Number of species currently existing: 10,105 species
Taxonomic Classification:
Domain: Eukaryota
Kindom: VI. Animalia
Phyla: B. Cnidaria
Class: Cubozoa (Box jellies) Swimming
Class: Scyphozoa (Jellyfishes) Swimming
Class: Anthozoa (Anemones and corals) Sessile
Class: Hydrozoa (Hydra) Both

6. Characteristics

7. Found in marine environments.
Two basic body types:
Polyps
Medusae
Tentacles
Venomous cell organelles (cnidea)
Gastrovascular cavity
Three-layered body; epidermis, mesoglea and gastrodermis
Radially symmetric
Carnivorous
Solitary or colonial
Asexual and/or sexual reproduction
Nervous system
No cardiovascular system

10. History

11. Fossil history:
Vendian/ Ediacaran period
650 to 540 million years ago
Soft-bodied organisms
Cambrian period - coral fossils
Early Ordovician - more developed corals

12. Generalized Life Cycle And Life Expectancy

13. Life span is undetermined.
Life cycles vary by class and species
Some skip stages (e.g. Hydra)
Alternation of generations (e.g. Obelia)
Asexual reproduction medusae grows on external tissue
Matured medusae swim away
Sexual cells released
Eggs are fertilized
Zygote/planula settles and develops into a polyop

15. Digestive System

16. Absorb dissolved organic chemicals
Filter food particles
Nutrients from endosymbiotic algae
Predate
Crustaceans and plankton
Medusae forms sink on top of the prey
Gastrodem layer releases enzymes that kill the prey
Cells absorb the nutrients
Nutrients spread by diffusion or mobile cells
Indigestible remnants are ejected

17. Respiratory and Circulatory System

18. No circulatory system
No respiratory organs
Absorb/expel O and CO2 into water
Water in digestive cavity is expelled

19. Sensory System

20. Simple sensory system
Net of nerves made of sensitive neurons
Sensitive neurons are connected by chemical synapse
Neuron sends neurotransmitter (chemical) to cell group

21. Bibliography New Oxford American Dictionary