Mollusks bivalves:gastro

1. Phylum Mollusca
Class: Gastropoda
Class: Bivalvia

2. Characteristics of Mollusca
•Protosome characteristics
•Coelom surrounds heart
•Open circulatory system (except cephalopods)

3. Class Gastropoda
Snails, Limpets and Slugs

4. Gastropoda
•Planning on being rich
and famous?
•Wining and dining at the
most expensive
restaurants?
•Romantic trips to Paris?
•Ever wonder what
Ceaser munched on
after long hard days
ruling the roman
empire?
•Than you should be
familiar with
ESCARGOT!!!!

5. General Body Plan:
Gastropod
•1. Head foot
•Head: sensory nerves,
mouth
–Anterior: near the head/
mouth
•Foot: attachment and
locomotion
–Posterior: near the anus
–Flattened w Cilia:
locomotion

6. That slimy foot…
•Snail Slime:
–Suction power: travel up
and down trees
–Escape: Emit a nasty
tasting slime when
threatened
–Movement: Allows them
to easily squeeze
through tight spaces
–Water Retention
•How Ms. Cota looks so
young:
–Skin regenerating
–used in skin beauty
products

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

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

9. 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

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

11. CFU
•How do mollusks exchange gasses
–Filter air through their gills
•Where are these gills located?
–The mantel
•What is the structure called that scrapes up
food?
–A Radula
•All mollusks have:
–A visceral Mass
–A head foot
–A mantel

12. Gastropoda
•Marine, Freshwater, Terrestrial
•Signifying feature: Torsion

13. Tosion
•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

14. Torsion

15. 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

16. CFU
•What is Torsion?
–The 180 degree twisting of internal organs
in snails
•How is Torsion adaptive?
–Pulls head in first, seals opening, locates
all sensory nerves in the front

17. Class Bivalvia
Clams, Oysters, Mussles,
Scallops

18. Bivalvia!
•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

19. 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

20. Foot
•Most mollusks have
foot that can be
used differently
–Attach mollusk to
surface
–Act as a lure to
attract prey
–Surround organs for
safety

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

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

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

24. CFU
•What is the technical term for the two halves
of the shell?
–Valves
•What structure filters water in and out of the
shell
–Siphon
•What is the function of the foot
–Attach mollusk to substrate, act as lure
•Why are bivalves important to humans?
–Pearls, food source, pollution filter
•How are humans affecting bivalves?
–Over harvesting, pollution, loss of current

25. Get ready for dissecfrtion!