Transcript WORM NOTES - Mahtomedi Middle School Geography

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 open circulatory
system
3. Obtaining Oxygen
a. most have gills
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.
b.
c.
d.
obtain food.
move.
protect themselves.
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 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.)
3.)
most without shells
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 mollusk
Gastropod:
Snails and slugs
How they obtain How they move
food
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:
Filter Feeders
Clams,
oysters,
scallops
float or swim –
some clap shells
together to
swim; muscular
foot to bury
themselves
Type of
mollusk
Cephalopod:
Octopus
Squid
Nautilis
Cuttlefish
How they
obtain food
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.
b.
c.
d.
head.
mouth.
shovel.
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.
B.
C.
D.
using jet propulsion.
moving their tentacles.
crawling along on a muscular foot.
gripping with their radula.
Answer
Using Jet Propulsion
Don’t be like this dumbo octopus
Use your…