Question

Give one example of hemichordata, urochordata and cephalochordata.

Answer 1

Hint:Animals can be distinguished on the basis of the existence of a backbone. Animals with a backbone or notochord are called chordates whereas non-chordates are animals lacking a backbone or notochord. Chordata is a phylum that comprises species such as mammals, fish, birds, reptiles and amphibians (all vertebrates); sea squirts (tunicates); and lancelets (cephalochordates).

Complete answer:
Protochordates are an informal group of species primarily referred to as invertebrate animals closely related to vertebrate animals. This group consists of Phylum Hemichordata and Subphylum Urochordata and Cephalochordata. They are distinguished by the appearance of a notochord at some point of their lives.

Hemichordata refers to any of a group of wormlike marine invertebrates closely related to both chordates and echinoderms. The Hemichordates are made up of three classes: Enteropneusta, Pterobranchia, and Planctosphaeroidea. An example of a hemichordate is Balanoglossus or acorn worm.

Urochordata is a subphylum of Chordata which includes the Tunicates and other classes such as Larvacea, Thaliacea etc. Tunicates or Urochordata are marine filter-feeding animals, found at all latitudes, and living mostly in shallow water. They are also known as “Sea Squirts''. An example of urochordata is Ascidia. In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life. Amphioxus, also known as lancelets, is an example of a Cephalochordate.

Note:Notochord is a long rod-like support system that extends around the back of the animal dividing the nerve tissue from the gut. It offers a place for muscles to attach for convenience of movement. Protochordates do not have a proper notochord present at all times of their life or for the full lifespan of the animal.