Ch. 2Ch. 2Sec. 1 MollusksSec. 1 Mollusks

How Can You Classify Shells?

• Examine each shell carefully. Look at the shape and color of the shells and feel their inner and outer surfaces.

• Classify the shells into 3 groups based on the characteristics you observe.

characteristics of molluskscharacteristics of mollusks

invertebrates soft, unsegmented bodies often protected by hard outer shells foot- used for crawling, digging, catching prey

characteristics of molluskscharacteristics of mollusks mantle= tissue that covers internal organs-produces hard shell gills= organs that remove oxygen from water open circulatory system= blood not always inside blood vessels

3 majorgroups

of mollusks

1. gastropods

2. bivalves

3. cephalopods

groupedgrouped intointo

classesclassesbased on based on

4 traits4 traits

presence of shell

type of shell

type of foot

type ofnervous system

1. gastropods• largest group of mollusks• single external shell or no shell• creep on broad foot • herbivores (eat plants)• carnivores (eat animals)• scavengers• radula= flexible ribbon of tiny teeth-scrapes food

• examples:1. snails 2. slugs (like snails but w/o shell)

• Gastropods use their radularadula to scrape food from a surface.

2. bivalves:

• 2 shells• do not have radula• most filter feeders- strain food from water• most omnivores (eat both plants & animals)• most stay in 1 place or move slowly

– examples:

1. clams- use thin foot to burrow into sand

2. oysters- attach to underwater surface

3. scallops- clap shells together to move

• A razor clam digs into the mud by changing the shape of its foot.

Clams move with the aid of their muscular foot.

3. cephalopods:3. cephalopods: • feet adapted to form tentacles around mouth• captures prey with tentacles• only mollusk w/ closed circulatory system• well developed eyes• most complex nervous system of any invertebrate• swim by jet propulsion

• examples: 1. octopus2. squid3. cuttlefish

Octopuses sense of touch is acute in their suckers. The rim of the cups are particularly sensitive.

Characteristics of Mollusks

Type of Mollusk

How They Obtain Food

How They Move

Gastropod

Bivalve

Cephalopod

Use radula to tear through plant or animal tissues

Filter feed

Use tentacles to capture prey

Creep along on a broad foot

Larva-Float or swimMost stay in one place

Swim by jet propulsion

Oceans Alive: Mollusks

Who is a mollusk?

It’s time to play….

a. smartest invertebrate

b. most are

filter feeders

c. capture prey with tentacles

d. swim by jet

propulsion

3 2 1Choose !Correct Answer !

a. insects b. bivalves

c. gastropods d. cephalopods

3 2 1Choose !

Correct Answer !

a.Have 2

shells

b. most are

filter feeders

c. Most stay in one place or move slowly

d. Swim by jet

propulsion

3 2 1Choose !

Correct Answer !

a. octopus b. squid

c. clam d. cuttlefish

3 2 1Choose !

Correct Answer !

a. Kind of foot b. Presence or

not of shell

c. Number of shells

d. Development

of embryo

3 2 1Choose !

Correct Answer !

a. clam b. oyster

c. cuttlefish d. scallop

3 2 1Choose !

Correct Answer !

Bivalve activity

• Use 2 paper plates to make a model of a clam. 

• Draw the organs on the inside of one of the plates and color the other light pink on the inside. 

• Color the plates to look like a shell on the outside. 

• Then, staple the two plates together to make a model of a bivalve. 

• For fun, you can get fake pearl beads and place inside the shell if the students make oysters. 

CLAM ORGANS

CLAM ORGANS