Echinoderm Diversity Part 3: Classes Echinoidea and Holothuroidea (Sea Urchins and Sea Cucumbers)

To finish things up with Echinodermata, we will look at class Echinoidea, the sea urchins, and class Holothuroidea, the sea cucumbers. What are these spiny things we call urchins? What is their anatomy like? What the heck is a sea cucumber? These are fascinating creatures, so let's learn about them!