Question

Both snail and tortoise have soft bodies covered in a hard shell. Yet, snail is grouped under Mollusca and tortoise under Reptilia. Why?

• A. Snail is small and tortoise is big
• B. Snail has no vertebral column while tortoise has one
• C. Snail has vertebral column
• D. Snail has limbs

Answer 1

The correct option is B Snail has no vertebral column while tortoise has one

The major difference between vertebrates and invertebrates is the presence and absence of the vertebral column, respectively. Phylum Vertebrata includes the classes Cyclostomata, Pisces, Amphibia, Reptilia, Aves and Mammalia. Invertebrates include the phylums Nematoda, Annelida, Mollusca, Echinodermata, etc. Though a snail has a hard shell over its body, it does not have a vertebral column. On the other hand, the tortoise has a hard shell and it also shows the presence of a vertebral column and possesses all the other characteristic features of the class Reptilia. Hence, Tortoise is classified under Reptilia while snail is classified under Mollusca.

So, the correct option is 'B'.