1. WORMS

2. Phylum: Platyhelminthes
Flatworms

3. General Characteristics
1. Organ level of development
First group to show sensory organs
2. Dorsally flattened
3. Digestive System
Pharynx (one opening)
5. Most are parasitic

4. General Characteristics
6. Are acoelomate
7. All are hermaphrodites
8. No specialized organs for respiration or circulatory system.
9. Excretion by flagella

5. Classes of Platyhelminthes

6. Class Turbellaria Commonly known as Planarians
Incomplete digestive system
Possess eyespots
Are photosensitive
Are monecious
Most species are marine
All have bilateral symmetry

7. Class Trematoda All are parasites No digestive system
Have complicated life cycle
Anterior and Ventral “sucker” used for attachment
Body covered by a tegument

8. Class Cestoda All are parasites Reproduce with cross-fertilization
No digestive system
Complex life cycle
Body made up of a scolex, neck, and proglottids.

9. Phylum Nematoda

10. General Characteristics
1. Most common of all worms
2. Range in size from less than a mm to more than a meter
3. Most are microscopic
4. Have a complete digestive tract with a separate mouth and anus
5. Covered by a “cuticle” made of collagen
6. Muscles are longitudinal

11. General Characteristics
7. Most are Dioecious
8. Larval stages resistant
9. No respiratory or circulatory system
10. Nervous system consists of a ventral nerve cord and a smaller dorsal nerve cord.

12. Phulum Annelida

13. General Characteristics
1. Bilateral symmetry
Segmented; also referred to as somites
2. Appendages in the form of small bristles known as setae or chaetae
3. Body covered with cuticle to prevent drying out
4. Digestive system with distinct regions

14. General Characteristics
5. Have a true coelom
6. Vascular system has 5 aortic arches (hearts)
7. Each segment is partitioned by internal septa
8. Respiration is dermal or by gills
9. Excretion is accomplished with a pair of nephridia (kidneys)

15. General Characteristics
10. Nervous system advanced.
Cerebral ganglia (brain), nerve cord, and lateral nerves
11. Reproduction
Asexually and Sexually depending on species
Monecious one carry out cross-fertilization

16. Class Oligochaeta Body with many segments No distinct head or tail
4 bundles of setae per somite used to move through soil.
Clitellum secretes the cocoon that contains fertilized eggs.
Monecuious reproduction.
Detritus feeder.
Respiration- Diffuses through skin.

17. Class Polychaete
Poorly developed head with 2 pairs of eyes and 5 pairs of parapodia (bristles)
Bristles evolved into defensive organs.
Parapodia used for locomotion respiration.
Dioecious

18. Class Hirudinea Have bilateral symmetry No setae
Have a triple jaw and an anticoagulant (hirudin).
Are parasitic to man.