MOLLUSKS AND UNIVALVES.pptx

Mollusks and Univalves

1. MOLLUSKS AND UNIVALVES BY VANCE JARRETT SANTOS GRADE 5 SIMON

2. MOLLUSKS There are over 50,000 known species of Mollusks, which makes them second only to the Arthropods in invertebrate phylum size. Among the Mollusks are some of the most well known of invertebrate sea creatures, like snails, clams, mussels, squid, and octopods. Mollusks are other animals with soft bodies. They live in the ocean, streams, ponds, and even in moist soil.

3. MOLLUSKS have 3 BODY REGIONS In general, mollusks have 3 body regions: a head , a visceral mass , and a " foot ." HEAD - contains the sense organs and "brain“ VISCERAL MASS - contains the internal organs “FOOT" - is the muscular lower part of the body which is in contact with the substrate Mollusks usually have a shell (although some do not). Mollusks also have an extension of the body wall called the MANTLE . This portion of the animal's anatomy is responsible for secreting the shell. The mantle encloses the mantle cavity which contains the Ctenidia (gills), anus and excretory pores.

4. MORE FUN FACTS ABOUT MOLLUSKS Many mollusks have a radula , a tongue of sorts, which is rough like sandpaper and is used to rasp away at food. The radula is made of a hard material called chitin , the same material of which Arthropod exoskeletons are made. In addition, some Mollusk radulae are impregnated with magnetite to give them superior wear characteristics.

5. MORE FUN FACTS ABOUT MOLLUSKS Mollusks have a digestive system with two openings and a circulatory system. They have gills , a special organ they use for absorbing oxygen from water. They have hard body coverings called shells that can be single, double or composed of several parts.

6. THREE TYPES OF MOLLUSKS 1. UNIVALVE OR GASTROPODS 2. BIVALVES 3. CEPHALOPODS

7. UNIVALVE OR GASTROPOD Univalves are as the name suggests – ‘one’ shell or a shell having one piece. Univalves are also known as gastropods . A mollusk with a univalve shell typically has a foot and head that live inside the shell and can extend or retract outside or inside the shell. Univalves can live in the water or outside the water. Examples of univalves include periwinkles, snails, abalone, and conchs.

8. MORE FUN FACTS ABOUT THE UNIVALVE The snail is a univalve mollusks that has one shell. It has a muscular foot along the ventral side of the body for crawling. Its foot releases slime where it glides. The body is covered with hard shell that protects it from its enemies.

9. HOW DO UNIVALVES GROW? Gastropods lay eggs. The eggs of some species contain a large yolk. Development of the eggs may be within the body, or the eggs may be expelled to develop externally. Eggs develop into larvae. Those species that will develop a shell start it while larvae. As the animal develops, it adds another curl of shell, ending in an opening from which the head and foot of the animal emerge.

10. WHAT DO THEY EAT? Gastropods feed on very small things. Most of them scrape or brush particles from surfaces of rocks, seaweeds, animals that don't move, and other objects. For feeding, gastropods use a radula, a hard plate that has teeth. Gastropod feeding habits are extremely varied, although most species make use of a radula in some aspect of their feeding behavior. Some graze, some browse, some feed on plankton, some are scavengers or detritivores, some are active carnivores.

11. EXAMPLES OF UNIVALVES Gastropods or univalves are the largest class of mollusks. Except for slugs, each has a single shell. Members of the univalve class are : * Snails * Slugs * Abalones * Whelks * Sea slugs * Conches

12. PREPARED AND PRESENTED BY : VANCE JARRETT SANTOS