Mollusca

The idea

Molluscs have soft bodies with organ system level organisation, a distinct head, a muscular foot and a hump; in many, a shell protects the soft body.

A snail and an octopus

A snail carries a shell. An octopus has no shell. Both have soft bodies.

What do you think a shell does for a soft body?

• Protects it
• Lets it fly
• Lets it make food from sunlight

Mollusc body

Open each tab.

Soft but protected

Molluscs have soft bodies with a head, a muscular foot and a hump. A shell protects the soft body in many of them. The book says the basic body plan can be modified in different directions depending on what the environment demands.

Molluscs have soft bodies with organ system level organisation, a distinct head, a muscular foot and a hump; in many, a shell protects the soft body.

Notes

Molluscs have soft bodies, organ system level organisation, a distinct head, a muscular foot and a hump; in many, a shell protects the soft body.

Check yourself

Which animals are molluscs?

What kind of body do molluscs have?

Which three parts does the book mention in the mollusc body?

What does a shell do in many molluscs?

• Snails, squids and octopuses — correct. Yes!
• Insects, crabs and spiders. These are arthropods.
• Starfish and sea urchins. These are echinoderms.
• A body with a hard external skeleton of jointed parts. A hard external skeleton is the defining feature of arthropods.
• A soft body — correct. Yes!
• A body with no organs. Molluscs show organ system level organisation.
• Tentacles, pores and a thallus. These belong to other groups. Tentacles are used by cnidarians, pores are in sponges and the thallus is in thallophytes.
• Wings, a backbone and a tail. The book does not describe molluscs this way.
• A distinct head, a muscular foot and a hump — correct. Yes!
• Protects the soft body — correct. Yes!
• Carries water through pores. Pores that carry water belong to sponges.
• Makes food by photosynthesis. Shells protect the soft body. Animals are heterotrophs.