1. Worms

2. Background Thousands of species in a wide variety of shapes and sizes
Inhabit water, soil, inside trees, and even insides of animals
Three major Phyla: Platyhelminthes (Flatworms), Nematodes (roundworms), and Annelids (Segmented

3. Platyhelminthes (Flastworms)
Flat body with bilateral symmetry
Most simple worms
No true body cavity and no extensive organ development

4. Platyhelminthes (cont..)
Anterior end (head)
Specialized for sensory perception
Ganglia on sides for sensing
physical stimulation
Eye spots for sensing light
Mouth that serves as entrance and exit of food and wast

5. Nervous System Consists of network of large ganglion
Eyespots to sense light
No circulatory system and no blood

6. Reproduction Asexually Binary Fission (results in two individuals)
regeneration

7. Nematodes (roundworms)
Round, tapering body with bilateral symmetry
Over 12,000 known species
Digestive System
Mouth at one end and anus at posterior end (one-way passage of food)
Has pharynx and intestine
Reproduction
1. Only reproduce sexually and have separate sexes

8. Annelids (segmented worms)
Bodies with segments
Bilateral symmetry
i.e: leeches, earthworms , and bristle worms
Coveres with Mucous and tiny hairs called setae for movement
Tube-within-a-tube body plan-internal organs are separated from other body parts

9. Digestive system
Esophagus transports food to the following: crop for storage, gizzard for grinding, and intestine for digestion

10. Circulatory system Contains blood vessels
Five pairs of “hearts” which pump blood

11. Nervous and reproductive System
Simple brain with ganglia (each segment contains ganglia)
Poorly developed sensory organs
Hermaphroditic
Sex organs located in clitellum