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Information obtained from: Holt Science and Technology: Life Science. Austin: Holt Rinehart & Winston, 2007. Print.
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CHAPTER 15 SECTION 2
Mollusks & Annelid Worms
Objectives:
Explain how mollusks eat, control body functions, and circulate blood
Describe the 4 body parts that most mollusks have in common
Describe the 3 kinds of annelid worms
Mollusks & Annelid Worms:
More complex animals than sponges, cnidarians, flatworms, roundworms
Have a circulatory system
Eaten by people! (oysters, mussels, clams, snails, squid, octopus…)
Earthmovers (earthworm activity aerates the soil)
Mollusks:
Most live in the ocean, some in freshwater & on land
3 classes: Gastropods (slugs & snails)
Bivalves (clams, shellfish)
Cephalopods (squids, octopuses)
How do Mollusks Eat?
Slugs & snails eat with a radula (tongue with teeth)
Clams & oysters cling to surfaces and use gills to filter particles from the water
Octopuses & squids use tentacles to grab food and put into their jaws
Mollusks: Ganglia & Brains
Complex ganglia to control breathing, movement, and digestion
Octopuses & squids have advanced nervous systems Large brains that connect all ganglia Cephalopods are considered the smartest invertebrates
Mollusks: Pumping Blood
Circulatory systems: transports materials through the body in the blood
2 Kinds: Open circulatory system: most mollusks
Simple heart pumps blood through blood vessels that empty into sinuses (spaces in the animal’s body)
Closed circulatory system: squids & octopuses Heart pumps blood through a network of blood vessels
that form a closed loop
Mollusk Bodies:
Bodies have similar structures even though the outward appearance is different.
Foot (movement)
Visceral mass (gills, gut, and other organs in center of body)
Mantle (layer of tissue that covers the visceral mass)
Shell (for protection, keeps it from drying out)
Annelid Worms:
Segmented worms (identical repeating body parts)
Bilateral symmetry
More complex than other worms
Closed circulatory system
Complex nervous system with a brain
Live in salt water, fresh water, or land
Annelid Worms:
Earthworms 100 to 175 segments; each segment has a job Eat material in the soil; decompose material and leave castings
Move using stiff hairs
Marine Worms Beautiful! Polychaetes (many bristles); many colors Most live in the ocean; eat mollusks, small animals, and
filter
Leeches Parasites that suck blood, some are just scavengers, or
predators Used in medicine to prevent swelling and clotting
Annelid Worms:
http://www.biopharm-leeches.com/images/hand.jpg http://habitatnews.nus.edu.sg/news/pulauhantu/images/marinewormblog.jpg
Quick Quiz:
What are the 3 main classes of mollusks?
How do herbivorous snails and slugs use their radula to obtain food?