Question

The unsegmented animals with a soft body is known as
A. Annelida
B. Arthropoda
C. Mollusca
D. Platyhelminthes

Answer 1

Hint: The different classification of the living organism is based on their characteristics. Organisms with similar types of characteristics are classified under a single group. The classification of organisms helps in the selection, identification as well as naming that are required for scientific studies.

Complete answer:
The living organisms are classified into the invertebrates and the subphylum Vertebrates. The invertebrates are known as the lower animals and were also known as the non-chordates. These animals do not contain a vertebral column that is known as notochord. The invertebrates do not have a skeleton, no notochords and represent less complexity in terms of body organization as compared to the vertebrates. The invertebrates are classified into different phylums which are Porifera, Ctenophora, Aschelminthes, Platyhelminthes, Annelida, Mollusca, Arthropoda and Echinodermata.

-The phylum Mollusca represents the animals that have an unsegmented and a soft body. In molluscs, the soft body is protected by a hard covering like structure which is known as the mantle. They are bilaterally symmetrical organisms and are triploblastic. They consist of a radula which is the rasping organ and it helps in feeding, e.g. pila, aplysia.
-Annelida is represented by the round segments which are known as metamers. They have a bilaterally symmetrical, triploblastic body. They are found in both freshwater and marine habitats and also in soil. They bear parapodia and setae for locomotion, e.g. earthworm, nereis.
-Arthropoda are the organisms that bear jointed legs or appendages. They are segmented organisms and bear an exoskeleton. Body is divided head, thorax and abdomen and the head bears compound eyes and tentacles. The most common examples of this phylum are cockroach, butterflies and prawns.
-Platyhelminthes are the flatworms and the body is dorsoventrally flattened. The body is soft and unsegmented but few species represent segments such as T. solium. They are acoelomate and are mostly parasitic in habitats but few are free livings.

Hence, the correct answer is option (C).

Note: The molluscs are the soft bodied animals. The soft body is protected by a hard covering which is made up of calcium. They are unsegmented organisms. They bear a radula which is a rasping organ and bears teeth. The radula helps in the feeding.