The document summarizes the three major classes of mollusks - Gastropoda (snails and slugs), Bivalvia (clams and oysters), and Cephalopoda (octopuses, squid, and cuttlefish). It describes their general body plans, anatomy, locomotion, digestion, respiration, reproduction, ecological roles, and adaptations for predation. Mollusks exhibit a diversity of forms and play important roles in both marine and terrestrial ecosystems.

1. Phylum Mollusca
Class: Gastropoda
Class: Bivalvia
Class: Cephalopoda

2. Class Gastropoda
Snails, Limpets and Slugs

3. General Body Plan:
Gastropod
• Characteristics
– 1. Head foot
• Head: sensory nerves, mouth
• Foot: attachment and locomotion

4. General Body Plan:
Gastropod
2. Visceral Mass
– Organs of
digestion
– Circulation
– Reproduction
– Excretion
– Dorsal to the
head foot

5. General Body Plan:
Gastropod
3. Mantle (shell)
– Attached to visceral
mass
• Encloses most of the
body
– Protection
4. Mantle Cavity:
– Gas exchange
– Elimination of digestive
wastes
– Release of reproductive
products

6. That slimy foot…
• Snail Slime:
– Escape
– Movement
– Water Retention
• Ecological Roles:
– Skin regenerating
– used in skin beauty products
• http://www.youtube.com/watc
h?v=JhRwcPRy6l4&safety_
mode=true&persist_safety_
mode=1&safe=active

7. Respiration
• One Gill in mantle
cavity
– Oxygen is taken in
– Diffused through the cells
• Open Circulatory
System
– Pushes blood in to
expand
– Pulls it out to contract

8. • Digestion
– Scrape algae
– Enzymes break down
food in stomach
• Radula: Scraping
mouth
– Chitinous belt & curved
teeth
• Covers fleshy tongue
• Muscles move it back
and forth
• Conveyor belt

9. Torsion
• Benefits
– Head enters first:
protection
– Operculum seals
opening to prevent
drying out
– Allows clean water to
enter mantle cavity
– Makes snail more
sensitive to stimuli
coming from the front

10. Reproduction
• Monoecious: can be
whatever sex they
want!
– Internal cross
fertilization
– One snail acts as
female one acts as
male
– Deposit eggs in
gelationous strings

11. Class Bivalvia
Clams, Oysters, Mussles,
Scallops

12. Structure
• Two halves of a shell:
Valves
– Adductor muscles hold
valves shut
• Visceral Mass
• Mantel Cavity
• Gills
• Cilia
• Siphon:
– filters water in and out of
shell

13. Foot
– Attach mollusk to
surface
– Act as a lure to
attract prey
– Surround organs for
safety

14. Ecological Roles
• Edible
• Commercial value:
Form Pearls
• Valuable in removing
bacteria from polluted
water!
– Rely on water currents to
get food
– Filter in nutrients, filter
out clean water
• Valuable food source:
humans, raccoons,
otters, birds

15. Digestive System
• Food comes in
through gills
– Sorted
– Digested
– Waste forcibly
pushed out of mantle
cavity by valves
shutting quickly

16. Respiratory System
• Respiration: Cilia in
gills move water into
mantel cavity
– Water tubes
exchange water to
blood through
diffusion
– Water exits bivalve

17. Human Interaction
• Many, many
mollusks are
threatened or
endangered
– Over harvesting
– Pollution
– Loss of habitat
– Loss of water
currents

18. Mollusks: Cephalopods
Octopus, Squid, Cuttlefish

19. Physical Characteristics
• Anterior
– Tentacles and jet
propulsion
• Mantle (Shell)
– Nautilus: only
cephalopod w external
shell
• Fills it with gasses to
help w buoyancy
– Squid: internal shell,
helps with structure
– Octopus: NO SHELL

20. Locomotion
• Jet like propulsion
out of mantle
– Squid: uses it for
catching prey
• Up to 25 mph!
– Octopus: escape
method

21. ECOLOGICAL ROLE
• Fierce Predators
– Large brains
– Complex sensory structures
– Rapid locomotion
– Grasping tentacles
• http://www.youtube.com/watch?v=p9A-
oxUMAy8&safety_mode=true&persist_saf
ety_mode=1&safe=active

22. Digestion
• Enzymes digest
food in stomach
– Moves to anus
– Expelled during
jet propulsion

23. Giant Squid Dissection
• http://www.youtube.com/watch?v=d83n
SFEoz2A&safety_mode=true&persist_s
afety_mode=1&safe=active

24. Predator Adaptations
• Locate prey by sight
• capture prey w
tentacles/ suction cups
– Tentacles reinforced w
protein
• Eat using a radula
– Cuttlefish: small
invertebrates
– Octopus:
• Nocturnal:
snails, fish, crustations

25. Predator Adaptations
• Chromatophores
– Cells that can change colors
• Tiny muscles contract or expand
and chromatophores quickly
change color
– Alarm response
– Defensive
– Blend in w environment
– Courtship
– Bioluminescence
• http://www.youtube.com/watch?v=t-
LTWFnGmeg&feature=related&safe
ty_mode=true&persist_safety_mod
e=1&safe=active