Question
Question: Identify the animal (A) and name the phylum to which it belongs (B).  and name the phylum to which it belongs (B).
A
a. A - Balanoglossus, B - Hemichordata
b. A - Balanoglossus, B - Cephalochordata
c. A - Nereis, B - Urochordata
d. A - Nereis, B - Annelida
Solution
The given diagram is elongated, symmetrical, bilaterally symmetrical and richly ciliated. This body looks unsegmented and divided into three regions: Proboscis, collar and trunk. These all features belong from hemichordates.
Complete answer:
As we can see in the diagram, the animal is elongated, symmetrical, bilaterally symmetrical and richly ciliated. There is no segment on the body and the body is divided into three regions: Proboscis, collar and trunk.
So, our first option is A - Balanoglossus, B -Hemichordata. Balanoglossus is an ocean-dwelling acorn worm. It resembles an earthworm. Its body is long like a worm like, it is cylindrical. The body of Balanoglossus is composed of an anterior part proboscis, a collar and a long trunk and it belongs to phylum hemichordata.
The 2nd option is A - Balanoglossus, B - Cephalochordata. As we already mentioned, Balanoglossus belongs to the phylum hemichordata.
The 3rd option is A - Nereis, B - Urochordata. The body of Nereis is dorsoventrally flat, which is segmented and having 80 to 120 segments and divided into acorn, trunk and pygidium. It belongs to the phylum annelida.
The last option is A - Nereis, B - Annelids. As we already mentioned about Nereis, which have a segmented body. So, the given diagram is of Balanoglossus, which belongs to the phylum Hemichordata.
Hence, the correct answer is option (A), A-Balanoglossus, B-Hemichordata.
Note: The length of Balanoglossus is 3 cm to 2 meter. Different species of Balanoglossus will show different colors. They are light brown or yellow or light red in colour. Balanoglossus is also called the connecting link between chordates and non - chordata.