What is the difference between saving an Excel file in .xlsx and in .csv? Would it be better to import into R using .xlsx or .csv?
The phylum Echinodermata, which contains about 6000 species, gets its name from the Greek, literally meaning âspiny skin.â This phylum exists exclusively in the sea and includes sea stars, urchins, brittle stars, and sea cucumbers. They are simple animals, lacking a brain and complex sensing organs.
Skeletal Composition. Echinodermata means spiny skinned.. Surprisingly, the external spines are composed of the same material as the internal skeleton. Calcium carbonate and protein form the rigid inner skeleton, or ossicles, of echinoderms.The exoskeleton is composed of soft, spongelike micro-structures called stereom.he uniform symmetry of echinoderms sets the creatures off from other marine life. All echinoderms are pentameral -- they have limbs in multiples of five. This trait is easily recognizable in starfish and brittle stars with only five limbs.