Question

Both snail and tortoise have soft bodies covered in a hard shell. Yet, the snail is grouped under Mollusca and tortoise under reptilia. Why?
(a) Snail is small and the tortoise is big
(b) The snail has no vertebral column while the tortoise have one
(c) The snail has a vertebral column
(d) Snail has limbs

Answer 1

Hint On the basis of the presence or absence of the notochord, kingdom Animalia is divided into two classes namely vertebrates and invertebrates where the organisms in the phylum Mollusca and reptilia are divided.

Complete answer:
Kingdom Animalia is broadly classified into two types on the basis of the presence or absence of the vertebral column. They are vertebrates and invertebrates. The animals which lack notochord are called invertebrates and those which contain notochord are called vertebrates.
Both snail and tortoise contain shells but snails are classified under invertebrates because they are devoid of the notochord whereas in tortoise notochord is seen.

Additional information:
-The class invertebrates of kingdom Animalia is classified into many phylums namely Porifera, cnidaria, Ctenophora, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, and hemichordata. Each phylum is divided into different classes.
-Phylum Mollusca t is divided into seven classes namely Aplacophora, Polyplacophora, monoplacophora, Gastropoda, Scaphopoda, pelecypods, and Cephalopoda.
-All the vertebrates are included in the phylum chordate which is divided into subphylums namely Urochordata, Cephalochordata, Vertebrata, and tetrapods
- Tetrapods are divided into amphibians, reptiles, aves, and mammals.

So, the correct answer is The snail has no vertebral column while the tortoise have one’

Note: After Arthropoda, the phylum Mollusca is the largest phylum in the animal kingdom. Examples of Mollusca are a snail, neomenia, galatha, aplysia, etc. neopilina was collected from the deep sea of the pacific ocean in Costa Rica in the oceanic research vessel called Galathea.