Student Resources

Echinodermata -Workbook Questions

What are the different types of symmetry that animals can have?  (p. 89)

The following symmetries can be found in animals: asymmetric, spherical, radial, biradial, and bilateral.

How do sponges and cnidarians trap and capture their food?  (p. 90)

Sponges are filter feeders. Flagella on their collar cells create water currents that draw water, and the food suspended in it, toward the collar and through the small spaces between the collar’s microvilli. Water passes through the spaces; food is trapped on the surface of the collar and ingested by phagocytosis. Cnidarians capture their prey using the stinging cnidocytes on tentacles surrounding their oral opening. The tentacles put the captured prey inside the gastrovascular cavity, and extracellular digestion creates particles small enough for the nutritive muscular cells lining the gastrovascular cavity to ingest by phagocytosis. Flagella on the different cells of the gastrodermis keep the contents of the gut mixed. 

What are the different parts of the water vascular system, and how are they connected to each other?  (p. 90)

The external opening to the water vascular system is the madreporite, connected to the stone canal and connected to the ring canal surrounding the oral opening. Radial canals extend from the ring canal down each arm, or ambulacral groove, and are connected to lateral canals, and in turn, the tube feet. Each tube foot has an internal ampullae and external podium and can be isolated from the rest of the water vascular system by a valve at the junction of the tube foot and the lateral canal. Tiedemann’s bodies and polian vesicles are often connected to the ring canal. 

Why are plants considered a nutrient-poor food?  (p. 92)

Large biomolecules, protein and carbohydrate, are what food is made of; but it’s only useful if it can be digested into smaller subunits or amino acids and sugar units. The most common carbohydrate in plants is cellulose, and animals can’t digest it. As a result, this potential carbohydrate nutrient is unavailable. To make matters worse, the cellulose is the main constituent of the cell walls that surround the cellular cytoplasm, filled with nutrients that animals can digest. To get the nutrients, they must grind and crush these cell walls to release the plant nutrients. The result is that they consume large amounts of plant materials to obtain small amounts of nutrients.

Protozoa || Porifera || Cnidaria || Platyhelminthes || Nematoda || Annelida || Mollusca || Arthropoda
Echinodermata || Chordate Origins || Jawed Fishes || Amphibia || Mammalia