PHYLUM MOLLUSCA

WHAT IS A MOLLUSK?

Why are animals that look and act so different grouped in the same phylum? It is because they share developmental patterns.

Characteristics of Mollusk1. mantle2. mantle cavity3. shell4. true coelom5. head, muscular foot, visceral

cavity6. systems: circulatory, respiratory,

digestive, excretory, reproductive, and nerve impulses

Mollusks are well defined as soft bodied animals that either have anexternal or internal shell.

Their name comes from the Latin word molluscus meaning soft.

– foot - flat surface adapted for locomotion and usually contains the mouth and other feeding structures

– mantle - covers most of the body and secretes the shell

– shell - composed of calcium carbonate

– visceral mass - contains the internal organ

Most mollusks are composed of 4 basic parts:

Unique features of most mollusks include

• MantleMantle

• ctendiactendia - special gill which are - special gill which are also used for filter feedingalso used for filter feeding

• radula radula - rasping tongue-like - rasping tongue-like structure used for scrapingstructure used for scraping

INTERNAL TRANSPORTOPEN CIRCULATORY SYSTEM

In open circulatory systems, the blood is not always contained in vessels. There is a simple heart and a few arteries but there are no veins. Blood leaves the heart and bathes the internal organs and travels through the body in open spaces called sinuses. These sinuses lead the blood to the gills where oxygen and carbon dioxide are exchanged (diffusion).

What is a closed circulatory system?

Excretion -All animals must remove waste

products An open circulatory system will work well for slow

moving animals. Why is an open circulatory system not adequate for

fast-moving animal