Question

Heart of hemichordates is
A. Ventral
B. Dorsal
C. Lateral
D. Absent

Answer 1

Hint: Hemichordata is a phylum of marine animals and is generally considered a sister of echinoderms. They are bilaterally symmetrical with a triploblastic body. Acorn worm is an example of Hemichordata.

Complete answer:
The hemichordates are free living muscular organisms which are exclusively marine. They are closely related to chordates but do not have notochord.

The structural features are:
- They have muscular bodies divided into anterior proboscis, intermediate collar and posterior trunk. Proboscis is a long tube like structure which the animal uses for burrowing.
- Mouth located in between the proboscis and collar.
- Trunks contain perforated gills, pharynx, food pipe, intestine and anus.
- A hollow neural tube is present.
- The circulatory system is open type and the heart is dorsal (back side).
- A rudimentary notochord like structure called the stomochord is present.

Ventral heart - The heart of the chordates is ventral. The human beings, birds, belong to the phylum chordata.
Lateral heart - Lateral heart is known as pseudoheart. It is present in earthworms.

Hence the correct answer is B. The heart of Hemichordate is dorsal.

Note: Open circulatory system is mainly found in in-vertebrates. The blood flows freely in the cavities as the vessels are absent to carry blood. For example the insects have an open circulatory system. The blood is pumped through the heart into the cavities and the tissues bathe in the blood. The flow of blood is slow.