Tag: zoology

Any wormlike invertebrate of the phylum Pentastomida (or subphylum of Arthropoda), having two pairs of hooks at the sides of the mouth: all are parasitic, some in the respiratory tracts of mammals.

Hemichordates are marine invertebrates which are closely related to both chordates and echinoderms. They are deuterostomes which have pharyngeal gill slits and most of them have a dorsal nerve cord and they lack a notochord.

Hemichordates means half chordates. It is a connecting link between non-chordates and chordates as they share some characteristics of both. The chordates have creatine in their energy cycle for the muscle contaction while non-chordates have arginine but the hemichordates have both i.e., creatine as well as arginine.

Protochordates are the animals having a dorsal hollow nerve cord, pharyngeal gill slits, and a notochord. They are usually referred to as the oldest chordates. They mainly include tunicates and cephalochordates. They are bilaterally symmetrical and possess a coelom. They do not have a closed circulatory system or jointed legs.

So, the correct answer is 'Both C  and D'.

Asterias ( star fish) is an example of echinodermata and not protochordata as they have a hard calcium carbonate structure that it uses as their skeleton.

Earthworm is an annelid, hydra is a coelenterate, liverfluke is a platyhelminthes, acorn worm (Balanoglossus, Saccoglossus) is a hemichordate belonging to class Enteropneusta.

Hemichordates consists of a small group of worm-like marine animals with an organ-system level of organization. They are nonchordates. The circulatory system is of open type. The blood flows to a cavity known as hemocoel which bathes the organs directly with oxygen and nutrients and there is no distinction between blood and interstitial fluid. They respire with help of gill slits.