The key difference between Mollusca and Echinodermata is the habitat they live in. Echinodermata are naturally marine, free-living or solitary sedentary and benthic, gregarious., etc These are symmetrical animals in radial manner with the symmetry of pentamerous . Notochord is a rod-like structure that separates the nervous system from the gut and also acts as a support. The main difference between chordates and protochordates is that the chordates are the animals that have distinct characteristics such as a notochord, dorsal nerve chord, pharyngeal slits, and a muscular tail whereas the protochordates are an informal group of invertebrates within chordates. It body will be elongated , and star shpaed as well spherical . The main difference between Hemichordata and Chordata is that Hemichordata contains an epidermal nervous system whereas Chordata contains a central nervous system. There are examples of other invertebrates that live in both fresh and salt water and on land. ⭕️ Echinodermata- These are the groups of animals under non-chordates that do not have notochord. Echinoderms in the larval stage have bilateral symmetry and as adults, they have radial symmetry. There are many interesting differences between these two animal groups, and the main distinction includes the presence or absence of the internal calcified, hard skeleton. They have a ventral nerve cord. The major difference between echinoderms and other invertebrates is that there are few examples echinoderms that do not live in ocean water and none live on land. Molluscs live in both terrestrial and aquatic environments. The organisms belonging to this phylum are generally found in marine environments. Molluscs have a hemocoel while echinoderms have a coelom. Echinoderms also display radial symmetry as do the jellyfish and sea anemones. Protochordata is a major division of Chordata. However, it is interesting to notice some of the echinoderms also have an internal skeleton. Mollusca and Echinodermata are two phyla that belong to the Kingdom Animalia. They are triploblastic organisms. They have a bilaterally symmetrical body without any head region.