molluscs

 

MOLLUSCS

CONTENTS

 

1. DEFINITION
2. EATING
3. REPRODUCTION
4. TYPES

DEFINITION

The two most universal of molluscs  are a mantle with a sicnificant cavity uses for breathing and excretion ,and the organization of the nervous system . The most abundant metallic element in molluscs is calcium .Molluscs have demeloped such a varied range of body structures ,it is difficult to find synapomorphies to apply to all modern groups  . The most general characteristic of molluscs is they are unsegmented and bliaterally symmetrical

 eating

Most molluscs  have muscular mouths with raadulae , tongues  , bearing many rows of chitinous teeth wich are replaced frok the rears as they wear out . The rádula prymarily funcstio to scrape bacteria and algae off rocks

repoduction

The simple molluscan reproductive system relies on external fetilization , but with more complex variations .All produce eggs , from wich many emerge trochophore larvae more complex velirge largae ,or miniature adults . Two gonads sit next to the coelom , a small cavity that surrounds the  heart and seds ova or spen into the coloem , from which the nephridia extract them and emit them into the mantly cavaty