Chapter 25.3, Problem 5MI

Summary Introduction

To list:

The structural differences between a snail and a squid

Introduction:

Snails and squids are animals that live in the ocean or on the beach. They belong to the phylum Mollusca. Members of this phylum range from slow moving snails to the jet- propelled squids. A mollusk has a soft body composed of a foot, a mantle and visceral mass that contains internal organs. Some mollusks have shells while others are without any outer covering.

Answer to Problem 5MI

The structural differences between a snail and a squid are:

1. Snail has a well- developed muscular foot whereas in a squid, the foot area is modified into arms and tentacles.
2. Snail has a shell whereas a squid does not have a shell.
3. A snail has two pairs of tentacles whereas a squid has two tentacles and eight arms.

Explanation of Solution

There are many structural differences between a snail and a squid. Some molluscs have shells such as snails while others are adapted to live without the hard outer covering. In a squid there is a reduced internal shell. The snail’s shell is secreted by the mantle and it protects the body of the snail by pulling the head and the foot inside the shell.

The snail has a well- developed muscular foot that enables it to move by contracting and expanding to create a rippling motion. In a squid the foot is modified into tentacles and arms that help in capturing and holding prey.

A snail has two pairs of tentacles on its head. The shorter pair is used to smell and feel whereas the longer ones have eyes on the tip. A squid has only one pair of tentacles but eight arms with which it captures the prey.