Weeks 9, 10: Cnidaria,Ctenophora, and coral reefs

Weeks 9 and 10: Cnidaria, Ctenophora and Coral Reefs

Note: Cnidaria is the more updated name for phylum Coelenterata, so we will be using that term.

Read chapters 6 and 7 in The Seaside Naturalist. These are some of the meatiest chapters we’ve covered yet. There is a lot of information here. Take your time. You have two weeks to explore these fascinating creatures so don’t try to rush through them. My advice is to split the reading up into several sessions, taking notes on each as you go, and copying the diagrams into your notebook. Alternate the reading/note-taking sessions with hands-on activities related to what you have read. With that in mind, I make the following suggestions for entries in your notebook:

Diagrams (labeled, with descriptive paragraphs):

  • General Medusa and polyp body plans (p55)
  • Alternation of generations(hydroid and jellyfish life cycles)(p57)
  • Siphonophore structure (p59)
  • polyps of hard and soft coral colonies (p66)
  • Sea Gooseberry structure (p71)

Chart (use Excel or another spreadsheet program,  MS Word table, or draw by hand) of the different classes within phylum cnidaria, the organisms belonging to each class, and important distinguishing characteristics for each class. This will help you to keep track of the taxonomy of the many different organisms within phylum Cnidaria.

Vocabulary: as you read, take note of any vocabulary that is new to you (ex: zooxanthellae) and be sure you figure out what it means. Write them in your notebook if it helps you to remember them.

Hands on activities: The types of Cnidarians and Ctenophorans you can find will vary widely depending on your location. I suspect that not many of us are lucky enough to live near coral reefs (though we do happen to be that lucky). But at least some species of hydroids, jellyfish, and sea anemones can be found just about anywhere. Now is the time to look for them and see what you can find. Look in a wide variety of places–sea walls, jetties, dock pilings and abandoned boats are great places to find cnidarians, as are tide pools and rocky coastlines.  As you read through your book, take note of specific places you might want to look (such as hermit crab shells for pink “snail fur” hydroids).Try to find at least one example from each of the three classes of cnidarians (ctenophorans may be more difficult to find). Study them closely and take note of interesting structures and behaviors (try feeding corals, hydroids and anemones with some finely ground fish or brine shrimp). Do not touch coral–it is very fragile. Anemones are safe to touch gently, and jellyfish, well, touch the ones that are safe to touch (what do they feel like?), observe the dangerous ones from a distance. Sketch your finds in your notebook. Identify and label them.

Seeing the real thing in the wild is always the best option, but if you simply cannot get out to find any live organisms, you might consider the following options:

  • Visit your local aquarium or nature center, like the Miami Seaquarium, Georgia Aquarium, etc
  • visit a local aquarium supply shop (or pet shop) and observe the salt water tanks there.
  • Sometime restaurants or office buildings have awesome saltwater set-ups. See if you can hunt these down. It’s a good way to get close up without getting wet!
  • Another option is DVD’s. Try Netflix or blockbusters (or your library) for the  excellent Blue Planet DVD’s: Blue Planet: Coral Seas would be the appropriate episode for this week (all of the Blue Planet DVD’s are available to watch instantly on Netflix!! YAY!!!). I’d suggest watching this DVD even if you can get out to the reefs, it is so good!
  • another Netflix instant watch: IMAX Coral Reef Adventure
  • Online video clips: Here is a link to a page with many short videos of various Cnidarians:Cnidaria movies. Some nice jellyfish clips here.   Gorgeous soft corals and sea fans here. Ctenophores here. Enjoy!

***Younger kids may want to do the following:


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