Invertebrates

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Lophophorates have a lophophore, a horseshoe-shaped, suspension-feeding organ with ciliated tentacles

Lophophorates include two phyla: Ectoprocta and Brachiopoda

Ectoprocts (also called bryozoans) are colonial animals that superficially resemble plants

A hard exoskeleton encases the colony, and some species are reef builders

Slide 40

Fig. 33-14

Lophophore

(a) Ectoproct (sea mat)

Lophophore

(b) Brachiopods

Slide 41

Molluscs

Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids.

Most molluscs are marine, though some inhabit fresh water and some are terrestrial.

Molluscs are soft-bodied animals, but most are protected by a hard shell.

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All molluscs have a similar body plan with three main parts:

Muscular foot

Visceral mass

Mantle

Many molluscs also have a water-filled mantle cavity, and feed using a rasplike radula.

Slide 43

Fig. 33-15 Basic Body plan of a Mollusc

Nephridium

Visceral mass

Coelom

Mantle

Mantle

cavity

Heart

Intestine

Gonads

Stomach

Shell

Radula

Mouth

Esophagus

Nerve

cords

Foot

Gill

Anus

Mouth

Radula

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There are four major classes of molluscs:

Polyplacophora (chitons)

Gastropoda (snails and slugs)

Bivalvia (clams, oysters, and other bivalves)

Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)

Slide 45

Fig. 33-16 A chiton

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Gastropods

About three-quarters of all living species of molluscs are gastropods

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Gastropods

(a) A land snail

(b) A sea slug

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Most gastropods are marine, but many are freshwater and terrestrial species.

Most have a single, spiraled shell.

Slugs lack a shell or have a reduced shell.

The most distinctive characteristic of gastropods is torsion, which causes the animal’s anus and mantle to end up above its head.

Gastropods

Slide 49

Torsion - causes the animal’s anus and mantle to end up above its head.