Question

A marine cartilaginous fish that can produce electric current is
A)Pristis
B)Torpedo
C)Trygon
D)Scoliodon
Name the two major groups of fishes based on the composition of endoskeleton.

Answer 1

Fishes are aquatic. Paired and unpaired fins are present. Respiration occurs typically by gills. Each eye has a well-developed nictitating membrane, eyelids are absent. Lateral line sense organs are present. Heart is two chambered (S-shaped, venous heart) with sinus venosus and conus arteriosus.

Complete answer:
Based on the endoskeleton fishes are of two types namely:

Chondrichthyes:
1.They are marine animals with streamlined bodies.
2.Endoskeleton is made up of cartilage.
3.Notochord is persistent throughout life.
4.Their jaws are powerful. Mouth is located ventrally.
5.Teeth are modified placoid scales which are backwardly directed.
6.Kidneys are mesonephric.
7.Skin is tough, containing minute placoid scales.
8.Gill slits are separate and without operculum (gill cover). Except in the Chimaeras.
9.Air bladder or swim bladder is absent, so they have to swim constantly to avoid sinking.
10.Heart is two chambered one auricle and one ventricle).
11.Organisms belonging to this class are cold-blooded (poikilothermous) i.e. they do not possess the capacity to regulate their body temperature.
12.Organisms are predaceous, some of them have electric organs (e.g. Torpedo) and some possess poison sting (e.g. Trygon).

Now let us find solution from given options:
A)Pristis : it is also termed as sawfish. These fishes show anadromous migration.
B)Torpedo : it is also termed as electric ray. It possesses electric organs and can produce electric current.
C)Trygon : it is termed as poison sting. It produces poison that has damaging properties. D)Scoliodon : it is termed as dog fish due to its appearance .

Hence, the correct answer is option (B)

Note: Fishes belong to kingdom vertebrata. In vertebrates that are the organisms that possess the vertebral column the notochord is replaced by the vertebral column. It consists of five sub phylum fishes, amphibians, reptiles, birds and mammals. Fishes have two chambered hearts to possess double circulation.