Mollusks and annelid worms
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Chapter 2, Lesson 2. Mollusks and Annelid Worms. Objectives of the lesson. Explain how mollusks eat, control body functions, and circulate blood. Describe the four body parts that most mollusks have in common. Describe the three kinds of annelid worms. Mollusks.

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Mollusks and annelid worms

Chapter 2, Lesson 2

Mollusks and Annelid Worms


Objectives of the lesson

  • Explain how mollusks eat, control body functions, and circulate blood.

  • Describe the four body parts that most mollusks have in common.

  • Describe the three kinds of annelid worms.


Mollusks

  • Examples of mollusks are:

  • Snails

  • Slugs

  • Oysters

  • Clams

  • Squids

  • octopuses


Where do mollusks live?

  • Most mollusks live in oceans, but some live in fresh water, and some on land.

Classes of mollusks

  • Most mollusks fit into three classes:

  • Gastropods: including slugs and snails.

  • Bivalves: including clams and shellfish with two shells.

  • Cephalopods: including squids and octopuses.


How do mollusks eat?

A ribbon-like organ: a tongue covered with curved teeth

Mollusks

With tentacles

With radula

With gills

In octopuses and squids

In snails and slugs

In clams and oysters

They use tentacles to grab food and place it in their powerful jaws.

They use radula to scrape algae from rocks, chunks of tissue from seaweeds, or pieces of leaves from plants.

They attach to one place and use gills to filter tiny plants, bacteria and other particles from water.


Nervous system

  • All mollusks have complex ganglia.

  • These ganglia are specialized for breathing, movement, and digestion.

  • Octopuses and squids have the most advanced nervous system in all invertebrates as they have large brains that connect all their ganglia.


Pumping blood

  • Mollusks have circulatory system.

  • It transports materials through the body in the blood.

  • Most mollusks have open circulatory system; which is simple heart that pumps blood through blood vessels that empty into sinuses (spaces) in the body.


Pumping blood

  • Squids and octopuses have a closed circulatory system; in which a heart pumps blood through a network of blood vessels that forms a closed loop.


Body parts of mollusks

  • 1. All mollusks have soft bodies which is a muscular foot.

  • This foot helps them to move.

  • The foot makes the mucus that the animal slides along.


Body parts of mollusks

  • 2. Visceral mass with includes gills, gut and other organs.

  • 3. Mantle: which covers the visceral mass and protects the bodies of mollusks that do not have shells.

  • 4. In most mollusks, the outside of the mantle secretes a shell, which protects the mollusk from predators and keeps land mollusks from drying out.


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