Phylum Annelida includes segmented worms such as earthworms, leeches, and polychaete worms. Their bodies are divided into many segments separated by internal walls. They play important ecological roles such as aerating soil, being a food source, and breaking down material. Their bodies have three layers, a coelom body cavity, complete digestive system, and sexual reproduction through cross-fertilization. They also have a closed circulatory system, nervous system, respiratory organs, excretory organs, and can live in soil, water, or as parasites on hosts. The three main classes are Oligochaeta (earthworms), Polychaeta (marine worms), and Hirudinea (lee

1. SEGMENTED WORMS
Phylum Annelida
Ex. Earthworms, leeches,
polychaete (marine) worms

3. Annelids
• Body is divided into segments that are
separated by septa (internal walls between each
segment).
• Some body segments may carry one or more
pairs of eyes, several pairs of antennae, and
other organs.
• Sometimes called “bristle worms” becase of the
tiny chitonous bristles that they bear (except
leaches) called setae.

4. Characteristics of Phylum Annelida
• Body type: bilateral
• Ecological role:
– Parasitic
– Food source
– Aerate soil
– Breakdown material
• Body organization:
3 layers – endoderm,
mesoderm, ectoderm
• Body cavity: coelom
(first)

6. Coelom

7. Characteristics continued:
• Digestive system:
– complete with mouth
& anus
– Food first moves
through the crop,
where it is stored
– Then it moves through
the gizzard where it is
ground into smaller
pieces.

8. Characteristics Continued:
• Reproduction:
– Sexual:
Hermaphroditic
with cross
fertilization
– Asexual: NONE

9. Characteristics continued:
• Circulation: blood,
blood vessels & aortic
arches = closed (first)
• Nervous system: brain,
ganglion, nerves,
sensory organs
• Respiration: pharynx or
gills
• Excretion: nephridia,
anus, tubes
• Habitat: host (external),
soil, water

13. 3 classes:
• Oligochaeta – Earthworm
• Polychaeta – Marine worm
• Hirudinea – Leech
• Free living – earthworm & marine worm
• Parasitic - leech

14. Class Oligochaeta

15. Class Polychaeta

16. Class Hirudinea (leeches)

17. Diagram - Answers

18. Shape of Life - Annelids
• https://vimeo.com/37255842