Phylum Echinodermata

Let's take a look at the common characteristics found in Phylum Echinodermata, which includes the sea stars, sand dollars, sea urchins, and more! These spiny skinned animals share things like having complete digestion and are triploblastic, but they also have a very unique way of moving: WATER! Learn more about these characteristics and their water vascular system and look through two more videos to see them in action.

[mulan]

you seriously dont know how much you have helped me. i have finals comin up and this was extremely helpful. i literally binge watched all you videos in 9 hours haha

[blandp]

Wait! I am more closely related to a starfish than to an ant? Mind blown! Thanks for posting these lectures to youtube.

[matrixtitan]

Hi yeah Matrix here. Ok, here's what I think.
Sea stars are bilaterally symmetrical. I explain. For an organism to be radially symmetrical, all of it's divided parts must be identical(same). But in the case of sea stars, I'm not all that sure that that's possible because sea stars have an organ called the madreporite which it uses to draw or suck up water into it's water vascular system. Since it has only one of that, radial symmetry will be quite impossible because no matter how many times you divide it into numerous parts, only one part will have the madreporite. It's like having an Orange and its stalk. The only symmetry that can be gotten from it is bilateral because trying to divide that radially will just disprove the word radial since inly one or two or just a few will have parts of the stalk included and not all. Just saying ma'am. What do you think?