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, Scallop
s

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, otter
s, 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