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.
Echinoderms are characterized by their radial symmetry, water vascular system and internal skeleton. The most striking feature of all echinoderms is their pentamerous radial symmetry.That is, the body can be divided into five parts (or appendages) which point outward from the center of the body. Interestingly, although most mature echinoderms are radially symmetrical, the larvae usually have bilateral symmetry.haracteristic of all echinoderms is the presence of an internal skeleton covered with spines and skin. The skeleton varies with the type of echinoderms. In sea stars and brittle stars, the skeleton consists of multitudes of small calcareous plates called âossiclesâ that move with one another, forming flexible joints.