28.1    Phylum Annelida and Phylum Mollusca

	Earthworms, leeches and many segmented marine worms are annelids.
	Annelids and mollusks are protostomes.
	Both groups have a similar larval form called a trocophore.
	The beating of the cilia propels the larva through water and creates water currents that carry food into its mouth.
	Both groups have a true coelom.
	Some members are filter-feeders.
	Earthworms increase nutrients available to plants by breaking down large pieces of organic matter.

28.2    Structure and Function in Earthworms

	Three classes of annelids: Oligochaeta, Polychaeta and Hirudinea.
	Earthworms ( Oligochaeta), have four small setae on each segment and no parapodia.
	The worm shortens when longitudinal muscles contract.
	Crop is a temporary storage organ.
	Gas exchange takes place across an earthworm's skin.
	Gases must first dissolve in water in order to diffuse across the skin.
	Diffusion of gases can only occur if skin is moist.
	The muscular aortic arches function as simple hearts by contracting and forcing blood in the ventral blood vessels.
	Earthworms are hermaphrodites but can't fertilize their own eggs.
	Earthworms must find a mate to reproduce.

28.3    Annelid Diversity

	Fanworms live in tubes they form of mucus and sand.
	Clam worms, free swimming polychaetes, are common along coast of U.S.
	Leeches secretes chemical into wound that reduce pain and prevent the blood from clotting during feeding.
	These secretions help ensure the leech gets a long, full meal.

28.4    Structure and Functions in Mollusks

	All mollusks have a mantle - soft, outer layer of their bodies.
	Muscular foot is dominant feature of all mollusks.
	The foot has different forms in snail, clam and squid.
	The squid has a sharp, beaklike jaw to kill and tear apart prey.
	Mollusks have nephridia that function to excrete wastes from cellular metabolism similar to annelids.
	Squids have a complex brain and thick bundle of nerves called giant nerve fiber.

28.5    Mollusk Diversity

	Chitons eat algae using radula - tonguelike organ that protrudes from mouth.
	Gastropods have little exposed surface area which gases can diffuse because their bodies are covered with shells.
	In bivalves, water passes over gills and particles of food are trapped in mucus on gills.
	The foot of a cephalopod is considered to be tentacles which are fused to the head.
	Eyes of cephalopod are similar in structure to human eyes.

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