Worms

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

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

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

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

Reproduction Asexually Binary Fission (results in two individuals) regeneration

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

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

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

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

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