Mollusks & Annelid Worms Ch15.2 7th

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?