1. Chapter 2
Section 1

2. Background information about Mollusks
They belong to the phylum Mollusca
Live nearly everywhere on Earth
Most live in water
Mountain streams to the deep ocean
Some live on land in damp locations.
About Mollusks

3. Background Information about Mollusks Bilateral symmetry
All organs are located in 1 area.
Open circulatory system for the 1st time.
This allows an animal to be bigger
About Mollusks

4. The mantle also produces the mollusk’s shell.
What is a mollusk?
Invertebrate with a soft, unsegmented body that is protected by a hard outer shell.
They have a thin layer of tissue called a mantle over their internal organs.
The mantle also produces the mollusk’s shell.
Respiratory organ for land mollusks
Mollusks

5. They move with a muscular structure called a foot.
Mollusks
What is a mollusk?
They move with a muscular structure called a foot.
Different mollusks have feet adapted for different uses such as crawling, digging, or catching prey

7. Types of Mollusks
Clam
Oyster
Snails
Octopus
Scallop

8. http://videos. howstuffworks
Mollusk Videos

9. Organs within a Mollusk Pair of Kidneys: organs that remove waste
Gills: Organs that remove oxygen from water
Radula: Flexible ribbon of tiny teeth
Mollusk ORgans

10. Covered with tiny, hair like structures called cilia.
Mollusk Organs
Gills: found in most water-dwelling mollusks
They are attached to the mantle
Have a rich supply of blood vessels
Oxygen from the surrounding water diffuses into the blood and carbon dioxide diffuses out
Covered with tiny, hair like structures called cilia.
The beating movement of the cilia makes water flow over the gills.

11. Radula: Flexible ribbon of teeth Unique to this Phylum
Act like sandpaper
Scrape food from a surface such as a leaf
May have as many as 250,000 teeth
The arrangement of teeth are used to classify mollusks
Mollusk Organs

12. The broken pieces piled up on the ocean floor
After a mollusk died the shell broke into pieces due to waves and currents.
The broken pieces piled up on the ocean floor
The hard materials underwent a chemical change and became cemented together to form limestone
During this process some shells become fossils
Early Mollusks
What was the 1st evidence of mollusks?
Living in the oceans about 540 million years ago
The evidence for this comes from fossil shells in limestone rocks

13. How are mollusks classified?
Based on the presence of:
Presence of a shell
Type of shell
Type of foot
The arrangement of teeth in the radula
Complexity of the nervous system

14. Gastropods – most numerous Bivalves Cephalopods
3 groups of Mollusks
Gastropods – most numerous
Bivalves
Cephalopods

15. Gastropod means “stomach foot”
Gastropods
Gastropod means “stomach foot”
Foot is on the same side of their body as their stomach
Snails have a single, coiled shell
Slugs have no shell
Creep along on their broad foot
Some are herbivores, some are scavengers, and others are carnivores
When a snail is threatened it can pull into its shell also when it is dry out

16. Ex: Clams, oysters, scallops, and mussels
Bivalves
Ex: Clams, oysters, scallops, and mussels
Have 2 shells that are held together by hinges
Do not have a radula
Instead food sticks to the mucus that covers the gills
Cilia on the gills then removes the food

17. Found in all kinds of watery environments
Bivalves
Found in all kinds of watery environments
As adults bivalves stay in 1 place or move slowly
After their larval stage oysters and mussels attach to a surface underwater
Clams are active and burrow into the sand or mud
Scallops move from place to place

18. Octopuses, cuttlefish, nautiluses, and squids are all cephalopods
Tentacles can be 5 meters long
Capture food with flexible tentacles
Suckers on the tentacles receive taste sensations
They don’t have to touch something to taste it
Large eyes and excellent vision
Swim by jet propulsion

19. Undergo torsion: movement of the anus
Class Gastropoda
Undergo torsion: movement of the anus
Advantage: Balance and protection because the head retreats first into the shell
Disadvantage: Anus is near the mouth
If torsion didn’t happen the foot would go in before the head
Largest and most varied class
Aquatic and terrestrial
Many marine snails have poison-tipped mouthparts
Many serve as an intermediate host for trematode parasites in humans.
Mantle used as respiratory organ in land snails

20. Torsion

21. 2nd largest class of Mollusks
Bivalves – 2 shells
2nd largest class of Mollusks
Marine & Freshwater
3 shell layers
Outer protective layer
Middle layers made of calcium carbonate
Inner layer
Class Bivalvia

22. Between the mantle and inner layer a pearl is made.
The pearl is formed by the mucus fluid covering bacteria or a grain of sand that is irritating the muscle.
They have no radula – filter feeders
Mussels make pearls – clams do not.
Class Bivalvia

23. Outcompete native mussels
Problems:
Outcompete native mussels
Disrupt spawning of game fish
Prolific breeders which damage property
Settle on native mussels so that they cannot open
Damage pipelines
Minnesota has one of the greatest diversities of freshwater mussels in the U.S.
Introduced zebra mussel larvae in 1985/1986 to the Great Lakes region from Europe

24. Most complex of all invertebrates Octopus: shell is absent
Squid/ Cuttlefish: Shell is internal
Nautilus: Shell is external
Class Cephalopoda

25. Anterior foot is divided into a series of arms Marine Active Predators
Class Cephalopoda
Anterior foot is divided into a series of arms
Marine
Active Predators
Powerful beak-like jaw and radula
Large brain: capable of learning
Image-forming eye similar to vertebrates
Closed circulatory system
Blue-ring octopus have salivary glands with venom