Chapter 25.3, Problem 3MI

Summary Introduction

To state:

The define of the given terms.

Introduction:

The terms given in the question are associated with mollusks. They are soft-bodied, triploblastic, coelomate and bilaterally symmetrical animals. Most of them are aquatic and few are terrestrial and found in moist soil. They have a well-developed various system such as circulatory and digestive systems.

Explanation of Solution

Mantle:  It is a layer of tissue that lies between the shell and the body. It secretes calcium carbonate to form the shell. It forms a cavity between the mantle and the body.

Radula: The radula is tiny teeth made of chitin. Herbivore mollusks used radula to scrap and tear food and the predator mollusks use the radula to drill holes in the shells of their prey.

Gills: Most mollusks have true gills. these are also called ctenidia. gills are a system of filamentous projections forms respiratory structures meant for gaseous exchange.

Open circulatory system: A blood circulatory system in which blood moves through vessels into open spaces hemocoel around the body organs.

Closed circulatory system: A blood circulatory system in which blood moves entirely in blood vessels such as arteries and veins.

Nephridia: These are coiled tubular duct-like organs. A pair of nephridia is present on each segment of the earthworm. They filter and remove waste from an earthworm's body.

Siphon: A tube-like structure which is used to expel water taken into the mantle cavity of some of the mollusks such as octopuses and squids.