All phyla of animals are invertebrates with the exception that only two of the three subphyla in Phylum Chordata are invertebrates: Urochordata and Cephalochordata.
Ubiquitous and filling diverse niches, invertebrates are integral to the ecology, productivity, and harmony of all ecosystems, and central to the extraordinary diversity of life that is so cherished by humans.
The exact number of phyla of invertebrates varies according to the taxonomic scheme.
The nematodes or roundworms are one of the most common phyla of invertebrates, with over 20,000 different described species, of which over 15,000 are parasitic.
Invertebrates include simple organisms, such as sponges and flatworms, and more complex animals, such as arthropods and molluscs.
Today, invertebrates are classified into about 30 phyla.
Echinoderms are a phylum of marine invertebrates found at all depths.