1. 27-3 Annelids

2. Septum
• Internal wall between the segments of an
annelid’s body

3. Seta
• Bristle attached to the segments of many
annelids

4. crop
• In earthworms, part of the digestive system in
which food can be stored; in birds, structure at
the lower end of the esophagus in which food
is stored and moistened.

5. gizzard
• In earthworms, part of the digestive system in
which food is ground into smaller pieces; in
birds, a muscular organ that helps in the
mechanical breakdown of food

6. Closed circular system
• System in which blood is contained within a
network of blood vessels.

7. Gill
• Filamentous organ in aquatic animals
specialized for the exchange of gases with
water.

8. nephridium
• Excretory organ of an annelid that filters fluid
in the coelom

9. Clitellum
• Band of thickened, specialized segments in
annelids that secretes a mucous ring into
which eggs and sperm, are released.

10. Key Concept
• Annelids are worms with segmented bodies.
They have a true coelom that is lined with
tissue derived from mesoderm.

11. Key Concept
• Oligochaetes are annelids that typically have
stream-lined bodies and relatively few setae
compared to polychaetes. Most oligochaetes
live in soil or fresh water.

12. Key Concept
• Leeches are typically external parasites that
suck the blood and body fluids of their host.

13. Key Concept
• Polychaetes are marine annelids that have
paired, paddlelike appendages tipped with
setae.