WORMS

Phylum: Platyhelminthes Flatworms

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

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

Classes of Platyhelminthes

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

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

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

Phylum Nematoda

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

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.

Phulum Annelida

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

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)

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

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.

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

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