MOLLUSK NOTES Chapter 10, section 1

A. Characteristics of Mollusks 1. Body Structure a. Bilateral symmetry b. Digestive system with 2 openings

Characteristics of Mollusks 1. Body Structure a. Bilateral symmetry b. Digestive system with 2 openings c. Mantle – protects internal organs or produces the shell

Find the mantle

Top picture – squid Bottom picture – octopus In both animals, the mantle protects the internal organs. In a squid, it produces the internal shell.

Characteristics of Mollusks d. Muscular Foot - has different functions: crawling, digging, or catching prey

Muscular foot of an octopus

2. Circulatory System a. most have an open circulatory system

3. Obtaining Oxygen a. most havegills

B. Classification of Mollusks

Classification of Mollusks continued 1. usually classified by their physical appearance such as: a. Presence of a shell b. Type of shell c. Type of foot d. Presence of a nervous system

Three major groups of mollusks a. Gastropods 1.) Largest group of mollusks 2.) Have a single shell or no shell at all 3.) Include snails and slugs

Gastropods continued… 4.) Obtaining Food a.) Herbivores animals that eat only plants 5.) Radula – organ that is a flexible ribbon of tiny teeth used like sand paper to tear throuh plant tissue

Picture of a gastropod’s radula

Checkpoint Gastropods use their radula to… a. obtain food. b. move. c. protect themselves. d. clean their shell.

ANSWER…. Obtain Food

Gastropods continued 6.) Movement a.) has a muscular foot – secretsslime to help it move across the surface

b. Bivalves 1.) these mollusks have2 shells held together by strong muscles 2.) Obtaining Food a. filter feeders - capture food as water flows over their gills - food particles stick to mucus that covers the gills

Bivalves continued… 3.) Movement – don’t move quickly a.) young larvae can float or swim b.) adults stay put or use their foot to move slowly

Mantle – just for review Part of the mollusk that makes the shell It’s the soft tissue of the mollusk In a squid it’s the outside of the squid – the part you eat if you eat calamari.

Bivalves continued 4.) Protection a.) Grains of sand can get in and irritate the mantle b.) Mantle will produce a smooth, pearly coat over the sand and and this is what makes pearls

Cephalopods

Octopus

Squid

Nautilus – only cephalopod with a shell

C. Cephalopods 1.) ocean dwelling mollusk whose foot is adapted to form tentacles around its mouth 2.) most without shells 3.) only mollusks with a closed circulatory system

Cephalopods continued 4.) Obtaining Food a.) carnivores – meat eaters - capture prey using tentacles 1.) tentacles have suckers sensitive to taste and touch

Cephalopods continued 5.) Nervous System a.) most complex nervous system of any invertebrate b.) large eyes, good vision, large brains

An octopus is pretty darn smart estimated to have 300,000,000 neurons. An octopus has a "good" memory and can also learn.

How does this compare to others? Pond snail 11,000 Ant 250,000 Cockroach 1,000,000 Frog 16,000,000 Mouse 75,000,000 Octopus 300,000,000 Elephant 23,000,000,000 Human 100,000,000,000

Their eyes are similar to ours too… It has a cornea, lens, iris and retina. It can also focus and form images. It’s different from vertebrates in that it focuses light by moving the lens closer and further away from the retina. The vertebrate eye focuses by changing the shape of the lens. Another difference is that the eye of the octopus has NO blind spot since the nerve cells leave from the outside of the eyeball.

Cephalopods have image forming eyes

Cephalopods continued 6.) Movement a.) swim by jet propulsion 1.)) squeeze a current of water out of the mantle cavity and through a tube called a siphon

An octopus is very agile and can fit through spaces 1/10 the size of their bodies

Type of molluskHow they obtain food How they move Gastropod: Snails and slugs Use radula – tongue like organ to scrape and tear plant or animal tissue Creep along on a muscular foot leaving a slime trail

Type of mollusk How they obtain food How they move Bivalve: Clams, oysters, scallops Filter Feeders float or swim – some clap shells together to swim; muscular foot to bury themselves

Type of mollusk How they obtain food How they move Cephalopod: Octopus Squid Nautilis Cuttlefish Use tentacles to capture prey, crush prey in beaks, use radula to scrape and cut flesh Swim using jet propulsion (water squirts out siphon) to propel backwards

The foot of a cephalopod looks like a a. head. b. mouth. c. shovel. d. tentacle.

Answer… Tentacles

Which of the following is NOT true of ALL mollusks? A. They have shells. B. They have soft bodies. C. They have a mantle. D. They have a foot.

Answer Not all mollusks have shells

Cephalopods move by … A. using jet propulsion. B. moving their tentacles. C. crawling along on a muscular foot. D. gripping with their radula.

Answer Using Jet Propulsion

Don’t be like this dumbo octopus

Use your…