Sponges, Cnidarians, Flatworms and Round Worms

Sponges, Cnidarians, Flatworms and Round Worms What you’ll learn: Describe the structures that make up sponges and cnidarians Compare how sponges and cnidarians get food and reproduce Differentiate between flat and round worms Why it’s important: Studying the body plans of these organisms will help you understand the complex organ systems in other organisms

Sponges (not the square kind) Adult sponges are sessile because they don’t move to find their food. All sponges are filter feeders, meaning water flows through their bodies and tiny plankton get stuck and eaten Not many animals eat sponges, their soft bodies are supported by sharp, glass like material called spicules. They can also be covered in soft, squishy material called spongin.

Note Check 1. How does a sponge get its food? 2. How does spongin and spicules differ, which would be more difficult for a predator to eat?

Sponge Reproduction Sponges normally reproduce asexually. This means a piece of the original sponge (a bud) breaks off and grows into a whole new sponge. This new sponge is IDENTICAL to the old sponge. It is similar to a clone of the first one since it has the same genetic make up.

Cnidarians All cnidarians have tentacles that surround their mouths. These include sea jellies, sea anemones, coral, and hydra. The tentacles on these animals have stinging cells called nematocysts that are used to catch prey. (They can also sting humans) Since they all have radial symmetry they can catch food in any direction.

Note Check 1. Give 2 examples of cnidarians. 2. What type of symmetry do cnidarians have? 3. All cnidarians have ___________________.

Cnidarians- Body Forms Cnidarians come in two forms, juveniles and adults. Juvenile cnidarians are known as polyps. These are vase shaped and many times sessile. Adult, free swimming forms, are known as medusas. Sea Jellies are not very strong swimmers and often just drift with the current.

Cnidarian Life Cycle

Note Check 1. What do we call a juvenile cnidarian? 2. How are adults different from juveniles?

Flat Worms Flatworms are soft bodied animals made up of 3 layers of tissues. They have bilateral symmetry. Most flatworms are parasites that feed on a host. Tapeworms are a specific type of flat worm that lives in the intestines of its host, including inside humans. Most tapeworms are not directly ingested by humans but infect a first host, like a cow then pass onto the human when they eat infected meat.

Round Worms Round worms are the most widespread animal on Earth If you own a dog, you have heard of the dangerous condition called heartworm. This is just one type of roundworm. Roundworms are describe as a body like a tube inside of a tube. Roundworms and Earthworms are NOT the same animal. Roundworms are very diverse, some are decomposers, others are predators and like the heartworm, they can also be parasites.

Heartworm inside a Dog How could this affect a dog’s health? How can you prevent this?

Sponges, Cnidarians, Flatworms and Round Worms