Non Chordates (Invertebrata) upto Phyla level

Invertebrates — animals that lack a vertebral column — make up roughly 99 percent of all described animal species, spanning everything from the cellular-level sponges to the chordate-adjacent hemichordates. This section works through the ten major invertebrate phyla recognised in the Tamil Nadu Class 11 Zoology syllabus, in the order the classification tree in section 2.2 places them: Porifera and Cnidaria and Ctenophora (the Parazoa and Radiata grades), then the Protostomia phyla Platyhelminthes, Aschelminthes, Annelida, Arthropoda and Mollusca, and finally the Deuterostomia phyla Echinodermata and Hemichordata. For each phylum the same set of questions is answered: what level of organisation and symmetry it shows, whether and how it is coelomate, whether i …