Invertebrates

Page
6

Mouth

Anus

Mantle

cavity

Stomach

Intestine

Slide 50

Bivalves

Molluscs of class Bivalvia include many species of clams, oysters, mussels, and scallops.

They have a shell divided into two halves.

Slide 51

Bivalve

Slide 52

The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange.

Slide 53

Clam Anatomy

Mouth

Digestive

gland

Mantle

Hinge area

Gut

Coelom

Heart

Adductor

muscle

Anus

Excurrent

siphon

Water

flow

Incurrent

siphon

Gill

Gonad

Mantle

cavity

Foot

Palp

Shell

Slide 54

Cephalopods

Class Cephalopoda includes squids and octopuses, carnivores with beak-like jaws surrounded by tentacles of their modified foot.

Most octopuses creep along the sea floor in search of prey.

Slide 55

Cephalopods

Octopus

Squid

Chambered

nautilus

Slide 56

Squids use their siphon to fire a jet of water, which allows them to swim very quickly.

Squid

Slide 57

One small group of shelled cephalopods, the nautiluses, survives today.

Chambered

nautilus

Slide 58

Cephalopods have a closed circulatory system, well-developed sense organs, and a complex brain.

Shelled cephalopods called ammonites were common but went extinct at the end of the Cretaceous.

Slide 59

Annelids

Annelids have bodies composed of a series of fused rings.

The phylum Annelida is divided into three classes:

Oligochaeta (earthworms and their relatives)

Polychaeta (polychaetes)

Hirudinea (leeches)

Slide 60

Oligochaetes

Oligochaetes (class Oligochaeta) are named for relatively sparse chaetae, bristles made of chitin.

They include the earthworms and a variety of aquatic species.

Earthworms eat through soil, extracting nutrients as the soil moves through the alimentary canal.

Earthworms are hermaphrodites but cross-fertilize.