Echinoderm

Professor Dave explains.

In the previous tutorial, we went over some general information regarding phylum Echinodermata.

Now let's get into some more detail by examining echinoderm body systems.

Echinoderms generally have an endoskeleton, coelom, water vascular system, digestive system, hemal system, nervous system, and reproductive system.

Professor Dave explains.

After discussing the general anatomy and characteristics of phylum Echinodermata, it's time to get a sense of the diversity of this clade, which will take several tutorials.

Though the echinoderm phylum is still large, diverse, and ecologically significant, there was a time when at least twenty classes existed on Earth, as is evidenced by the fossil record.

Today, the five extant echinoderm classes are Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, and Holothuroidea.

Finally, the sea lilies of order Isocrinida have a long stalk with a series of cirri and a holdfast used for attachment to the substrate.

Though the sea lilies are much less mobile as adults than the feather stars, many are able to abandon a site if threatened, though often quite slowly.

And that covers just one of the extant classes of Echinodermata.

Let's move forward and check out some other classes.