1. CLAM DISSECTION

2. no bones around nerve cord
CLAMS ARE:
Invertebrates-
no bones around nerve cord
Protostomes- blastopore becomes mouth determinate spiral cleavage

3. Clam & octopus from: http://www. geocities

4. CLAM DISSECTION KINGDOM ___________ PHYLUM ____________ “Soft”
CLASS ______________ “2 shells”
ANIMALIA
MOLLUSCA
BIVALVIA
(Pelecypoda)

5. UMBO tells direction Anterior Posterior Dorsal Ventral
Image by Riedell/Vanderwal © 2005

6. Clams are SESSILE as ADULTS Don’t move much Stay in one place LARVA
swim with
CILIA

7. NO CEPHALIZATION (No head) Shell = valve (Bivalvia = 2 shells)
Growth rings - increase with age

8. ADDUCTOR MUSCLES
Turn POSTERIOR END toward door Cut your adductor muscles to open shell
Image from:

10. ANTERIOR & POSTERIOR ADDUCTORS

11. FOOT – points toward anterior end

12. VISCERAL MASS
Contains heart, digestive, excretory, reproductive

13. Mantle cavity (NOT COELOM)
Image from:
NO cephalization Gills hang OUTSIDE body in mantle cavity

14. Image modified from: http://www. lander

15. Hinge
Teeth on dorsal edge lock to keep shells from sliding

16. Smooth lining Irritants are coated by mantle to protect soft body
“Pearls”
Animation from:

18. Mantle produces shell (calcium carbonate makes it hard)

19. INCURRENT & EXCURRENT SIPHONS
move food
up toward
mouth
CILIA on gills pull in water

20. Image by: Riedell/VanderWal © 2005

21. SEXUAL REPRODUCTION SEPARATE SEXES Male & female clams
General term for reproductive organs
= GONADS

22. SEXUAL REPRODUCTION Marine (salt water) clams- external fertilization
(sperm or eggs exit through siphon)
Freshwater clams-
internal fertilization (sperm enters through siphon; fertilized eggs/larva exit )

23. Other mollusks GASTROPODS- internal fertilization
Land snails = hermaphrodites
Aquatic snails = 2 separate sexes
CEPHALOPODS- internal fertilization
Separate sexes –

24. Indirect development ADULTS-
Indirect development
TROCHOPHORE LARVA
Ciliated- can swim
ADULTS-
Sessile = stay in one place Can put out foot and crawl

25. GILLS Trap food (PALPS move it forward) Ridges for more surface area
(like typhlosole)
Gas exchange
Diffusion moves
oxygen & CO2
across membrane

27. GAS EXCHANGE IN GILLS
Image by Riedell
Diffusion moves from HIGH → LOW

28. OPEN CIRCULATION Blood flows loose inside coelom and tissue spaces
Heart pumps blood (HEMOLYMPH)
COELOM = SMALLER
mainly around heart
= pericardial cavity

29. OPEN CIRCULATION is less efficient way of moving oxygen, nutrients, and nitrogen waste
Doesn’t go directly to parts 
2. High oxygen and low oxygen blood can mix so it gets diluted

30. HEART & PERICARDIAL CAVITY

31. DIGESTIVE FILTER FEEDERS (strain food from water)
Food pulled in through incurrent siphon by cilia moving on gills
Food trapped in mucous on gills
Palps move food up and into mouth
esophagus  stomach
Digestive gland  
Intestine  anus

32. Makes BILE to break down fat Finishes digestion
DIGESTIVE GLAND
Makes BILE to break down fat Finishes digestion

33. carries digestive waste to anus
INTESTINE
carries digestive waste to anus

34. 3 Body systems use mantle cavity
EXCRETORY - Nitrogen waste from kidney
DIGESTIVE – feces released from anus
REPRODUCTIVE-
Sperm or egg (if external fertilization)
Larva (if internal fertilization)
Image from:

35. NERVOUS SYSTEM 2 pairs of nerve cords 3 pairs of ganglia