Echinoderms come in countless shapes and sizes, but there are a few unique features that unite the 6,500 living species. Many adults of this phylum have 5-way radial symmetry; a pattern most prominent in the shape of the starfish. In addition, they have skeletons made up of interlocking calcium carbonate plates and spines called ossicles. This provides rigidity for their complex structures, making up the protective shell of urchins, or the column-like spine of crinoids. These skeletons are also the reason why fossils for echinoderms are so widespread and well-preserved, with some crinoid fossils being as old as 500 million years. Perhaps the most peculiar creatures of this phylum are the holothurians. Sea cucumbers, with their retractable feeding tentacles and tube feet around the mouth which they use to forage in the sea floor mud.
00:00 - An Introduction to Echinoderms
01:27 - The Structure of Echinoderms
02:01 - Ossicles Explained
02:35 - Holothurians Explained (Sea Cucumbers)
02:53 - The Swimming Sea Cu
1 view
161
30
4 years ago 02:19:29 1
Damn, that’s interesting!
6 years ago 00:00:15 3.3K
damn boy that’s a thicc
7 years ago 00:02:21 25
damn that’s good
11 years ago 00:00:48 96
damn !!! that’s hard
11 years ago 00:02:06 98
Comedy Central’s Key & Peele: Damn, Check That S**t Out
4 years ago 00:00:22 249
Persona 4 Golden - damn that’s crazy bro but did I ask