NEET BIOLOGY

Detailed explanation-1: -A notochord is present in the phylum Chordata (comprising three subphyla: amphioxus, tunicates, and vertebrates) and, more arguably, in some other animals. Among invertebrate chordates (Fig.

Detailed explanation-2: -All chordates have a notochord at some stage in their lives, but in some (such as tunicates) the notochord is lost in the adult, whereas in others (such as the vertebrates) the notochord is present in the embryo, but in later stages is largely replaced and surrounded by the vertebrae, or backbones.

Detailed explanation-3: -Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, e.g., porifera to echinoderms.

Detailed explanation-4: -Phylum porifera, coelenterata and platyhelminthes are non-cordates.

Detailed explanation-5: -Non-chordates are animals without a notochord – the rod-like elastic structure that supports the body. This phylum consists of a small group of worm-like, marine species with an organ-system level of organization. Members of Porifera, Arthropoda, Mollusca and Echinodermata fall under Non-chordates.