1. Chapter 13: Phylum Mollusca pp. 329-334

3. Biology fun facts of the day:
Experts claim that about 1,000 oysters must be opened in order to find one usable pearl!

4. Biology fun facts of the day:
The common garden snail, Helix aspersa, can travel about 2 feet in 3 minutes. At that rate, it would travel 1 mile in 5.5 days.
(Now you know where the term ‘snail mail’ comes from!)

5. Biology fun facts of the day:
When we hold a large seashell up to our ear, you can hear what sounds like waves because the shell echoes all the sounds around you.
If you could listen to a shell in a completely soundproof room, you would hear nothing at all!

6. Biology fun facts of the day:
Many land snails can lift 10 times their own weight up a vertical surface. (If you were this strong, and you weighed 30 kg (about 70 lb), you could carry 300 kg (almost 700 pounds!!!) straight up a wall!

7. Introduction to Molluscs
Molluscs represent the second largest animal phylum, following the arthropods = Old Phylum (500 million years, approx.) 80,000 – 100,000 existing species (estimate) Most species are free-living Inhabit a variety of marine, aquatic & terrestrial habitats Important ecological roles with regards to nutrient recycling; bivalves clean and recycle sediments Empty shells provide habitat for other invertebrates

8. Where do Molluscs fit in?

9. Introduction to Molluscs
Phylum Mollusca – Latin molluscus = “soft”
Protostomes
Bilateral symmetry; eucoelomates
3 cell layers (ectoderm, endoderm, mesoderm)
Have a coelom (but often reduced to a cavity that surrounds only the heart)
Have trochophore larvae (free-swimming ciliated larva)
Similar larvae in annelids 
likely share a common ancestor

10. Introduction to Molluscs
Molluscs all share similar developmental patterns and a common body plan:
Foot (muscle; function varies)
Shell (protection; made of CaCO3)
Mantle (produces the shell)
Visceral mass (contains internal organs)
Diagrams of snail, clam, and squid p. 300

11. Classes of Molluscs 1) Class Bivalvia 2 hinged shells No head or eyes
Gills; live in water
Example members: clams, oysters, scallops
2) Class Gastropoda
One shell
Some are terrestrial
Example members: snails, slugs, nudibranchs

12. Classes of Molluscs 3) Class Cephalopoda Fast-moving predators
Foot is modified into tentacles
Well-developed nervous system
Some can use camouflage and jet propulsion (e.g. octopus) when they feel threatened
Example members: octopus, squid, nautilus, cuttlefish
Nautilus
Squid
Octopus

13. Squid are the largest Cephalopods

14. Colour and Morphology Changes = Camouflage

15. Form and Function of Molluscs
Molluscs vary a lot  clam = representative mollusk
Digestive system:
Complete digestive tract (mouth  anus)
Mouth, esophagus, stomach, intestine, anus
Have a radula (scraping/drilling organ) or a beak (cephalopods)
Bivalves trap food in their gills – no radula
e.g. Gastropod

16. Form and Function of Molluscs
Respiratory system:
Aquatic mollusks have gills
Terrestrial mollusks have a highly folded mantle for O2/CO2 exchange (must stay moist)
*A clam has incurrent and excurrent siphons  sea water passes through; location of gas exchange

17. Circulatory system:
Open circulatory system – the heart pumps blood through open spaces called sinuses instead of through blood vessels
Excretory system:
Nephridia (primitive kidneys) remove metabolic waste (nitrogen-containing wastes like NH3)
Digestive wastes go out anus

18. Bivalves – reduced nervous system; no head Gastropods – fairly basic
Cephalopods – very well developed
Good vision, small ganglia near mouth, statocysts (balance), simple chemical and touch receptors
Good dexterity and memory – they can learn!

19. Musculoskeletal system: Muscular foot for movement
Bivalves – “two shell”; foot pulls animal forward, and can be sucked back in (for protection)
Gastropods – “stomach foot”; they slide forward on broad ventral foot (use muscus)
Cephalopods – “head foot”; foot has been modified into many tentacles with suction cups
e.g. Gastropod

20. Reproduction:
Some Monoecious (have both sex organs, capable of producing both sperm and eggs)
Others are Dioecious (either male or female gonads, can produce one type of gamete only)
Separate sexes (usually)
External fertilization (broadcast method) in bivalves/marine gastropods)  the female traps sperm
Internal fertilization in cephalopods/terrestrial gastropods

21. Ecology of Molluscs
Bivalves used to check pollution levels – “environmental monitors”
Range of lifestyles: predators, scavengers, filter feeders, etc.
Crop damage – slugs, snails on land
Ship damage – shipworms in water
Food source for humans: clams, oysters, mussels, etc.
Humans can get poisoned by eating mollusks contaminated with toxic protists  cause “red tide”

22. Molluscs Movie!

23. Mollusc (5-7-5) Haiku:
Slow, slick, sliding slug Terrestrial explorer No protective shield
Create your own mollusc haiku in format!

25. Works Cited Images taken from the following sources:
26-like-being-home.html
facts-and-care-tips.html
phore.html
mollusks-clam-up-would-ya/

26. Works Cited
=TCESearchMedia&Params=A1&MediaId=385 control/ nautilus.html

27. Works Cited
/Clam%20Dissection/Clam_Dissection.htm classification- choose?commentId= %3AComment%3A10692&x g_source=activity ution.htm mollusks.htm