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CNIDARIA
Lesson 1 - Page 1

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The pieces in your kit represent only a small group that make up the Phylum Cnidaria. Corals are usually referred to when people talk about warm, clean areas like Florida, Hawaii or Australia. This is so, because coral are sensitive to changes in water conditions, without the right conditions the corals will not survive. The part that you have in your kit, is the skeleton that the animal makes. The animal itself has most of the characteristics listed above. Corals usually make good fossils because they leave behind their skeleton. The three types that you have represent two different types of living habits. The branching coral or stem coral is a colony. It is made up of many individuals that live together on a common skeleton. Each opening represents where each of the individuals lived. The mushroom and flower coral on the other hand is an individual. One animal made this skeleton. The many radiating walls (septa) helped support the animal when it was alive. Emphasize with your students the difference between colonies and individuals and to make sure they understand that the real animal looked like an upside down jellyfish, whose tentacles capture food.
KEY POINTS:
  • includes hydroids, jellyfish, sea anemones, and corals
  • lives near shore to deep ocean depths
  • ranges in size from one millimeter to several meters
  • all have radial symmetry
  • sac-like body has central body cavity
  • body wall consists of 3 layers
  • single opening serves as both mouth and anus and is surrounded by food capturing tentacles
  • stinging cells (nematocysts)
 

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