Category: Other invertebrates

The described species of animals are over one million. Of these, about 55 animals possess a backbone or vertebral column and are known as “Vertebrates”. The remaining animals which lack backbone or vertebral column are referred to as “Invertebrates”. As we have discussed about arthropods- the largest phylum among invertebrates, we will discuss the rest of the phyla here, viz. Protozoa, Porifera, Ctenophora, Platyhelminthes, Nematoda, Annelida, Mollusca, Echinodermata and Hemichordata. It has been confirmed by evolutionary studies that all the members of an individual phylum have been derived from a common ancestral type. Thus all these phyla display different patterns, each manifesting a characteristic, anatomical and functional integrity and common ancestry.