Radially symmetric animals with stinging cells, including jellyfish, corals and sea anemones.
Two body forms: polyp (sessile) and medusa (free-swimming). Cnidocytes with nematocysts fire stinging threads. A gastrovascular cavity has one opening. Nerve nets coordinate movement.
Cnidarians have a mouth ringed by tentacles. Medusa and polyp stages can alternate. Corals build reefs.
Key idea: cnidocytes are unique to cnidarians.
Radially symmetric animals with stinging cells, including jellyfish, corals and sea anemones.
Cnidarians is one of the 53 topics in Zoology & Animal Diversity. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Flatworms, Animal Skeletons, Animal Kingdom.
Corals are colonial polyps secreting calcium carbonate skeletons.
Cnidarians is a Beginner topic, so no earlier topic is required. Other Beginner topics in Zoology & Animal Diversity that pair well with it include Animal Kingdom, Vertebrates and Invertebrates, Sponges.
The closest topics to Cnidarians are Flatworms, Animal Skeletons, Animal Kingdom, Animal Symmetry. Comparing them side by side is a good way to see how the ideas connect.
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Cnidarians. To practise the whole of Zoology & Animal Diversity, use the Zoology & Animal Diversity quiz.
Cnidarians: Radially symmetric animals with stinging cells, including jellyfish, corals and sea anemones. Flatworms: Soft-bodied, bilaterally symmetric worms with no body cavity, including tapeworms and flukes. Read both side by side and note what each one explains.
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Flatworms and explain the difference aloud. Finally, take the Zoology & Animal Diversity quiz and come back to this page for any question you miss.
Soft-bodied, bilaterally symmetric worms with no body cavity, including tapeworms and flukes.
🦁 Zoology & Animal DiversityHydrostatic skeletons, exoskeletons and endoskeletons give support and enable movement.
🦁 Zoology & Animal DiversityMulticellular heterotrophic eukaryotes without cell walls that typically move and ingest food.
🦁 Zoology & Animal DiversityAnimals show radial, bilateral or no symmetry, which relates to their lifestyle and movement.
🦁 Zoology & Animal Diversity