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

Find the mantle

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

system open circulatory

3. Obtaining Oxygen

a.

most have

gills

B. Classification of Mollusks

Classification of Mollusks continued

1.

usually classified by their

physical appearance a. b

.

Presence of a shell Type of shell

such as:

c. d

.

Type of foot Presence of a nervous system

Three major groups of mollusks a. Gastropods 1.)

Largest group of mollusks

2.) 3.)

Have a single shell or Include snails and

no shell at all 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 – secrets

slime to help it move across the surface

b. Bivalves

1.)

these mollusks have

2 shells

together by strong muscles held

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.) 2.) 3.)

ocean dwelling mollusk whose foot is adapted to form

tentacles around its mouth

most without

system shells

only mollusks with a

closed circulatory

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  Mouse 16,000,000 75,000,000  

Octopus

Elephant

300,000,000

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

Type of mollusk Cephalopod: How they obtain food Octopus Squid Nautilis Cuttlefish Use tentacles to capture prey , crush prey in beaks, use radula to scrape and cut flesh How they move 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…