Phylum Platyhelminthes Flatworms Bilateral symmetry Acoelomate Lack a

Phylum Platyhelminthes (Flatworms)

• Bilateral symmetry • Acoelomate – Lack a body cavity(coelom) • 3 Layers : endoderm, ectoderm, mesoderm

• Gastrovascular cavity • Mouth – one opening • Cephalization-nerves and sense organs at anterior end

Class Turbellaria Includes marine worms & planarians *Most free living

• PLANARIAN • Movement: cilia on ventral surface/ muscle contractions • Digestive System: • Feeding: suction of pharynx (middle of body) • Gastrovascular cavity • No Respiratory/ Circulatory system: diffusion

• Nervous System: • Ganglia (simple brain) , 2 Nerve cords. Eyespot(senses light)

• Excretory System: • Flame cells- remove fluid waste

• Reproduction: • Sexual- hermaphrodite, cross fertilize • Asexual- regeneration

Class Trematoda -flukes (parasitic) • Leaf-shaped • Sucks blood, cell fluids • Sheep liver fluke: – 2 hosts: sheep, snail – Larva develop inside snail – Sheep eats grass with larva

Blood fluke Schistosoma causes disease Schistosomiasis

• Class Cestoda • Tapeworm • Parasite

• Body: absorbs nutrients; tegument/cuticle prevents parasite from being digested by host • Scolex- hooks and suckers that attach to intestinal wall (no mouth) • Proglottid- segment containing reproductive organs

Life cycle of beef tapeworm

Life cycle of beef tapeworm • Cow eats grass contaminated with eggs • Larva hatch and bore into intestine and enters bloodvessel • Burrow into muscle and form a cyst • Human eats beef that has not been cooked properly with cyst in it • Adult tapeworm forms in human’s intestine • Takes nutrients • Proglottid breaks off and eliminated in waste

Prevention: Worm livestock USDA inspection Cook meat

Dog/Cat Tapeworm • The tapeworm is transmitted to dogs and cats that ingest fleas (fleas eat tapeworm eggs) or eat wildlife / rodents infested with tapeworms or fleas. Proglottids in fur below tail

Tapeworm in fish/ heron http: //www. youtube. com/watch? v=dy 4 c. QO N 7 -JU&list=PLBA 01 CF 012057626 A

Phylum Nematoda (roundworms)

• Pseudocoelom (false cavity): located between endoderm and mesoderm • Fluid filled • O 2, CO 2, nutrients diffuse into fluid)

• Two openings : mouth and anus (tube in a tube) • Free living (most) : • live in all types of soil ( handful contains thousands): Most numerous animal on earth. • Feed on bacteria, fungi, other nematodes, organic matter

• Parasitic • Beneficial as a natural pest control • worm enters insect larva > worm releases bacteria > bacteria multiply/poison > larva dies Infected root Harmful Reduce plant vigor

Ascaris life cycle • • • Immature worms hatch from eggs in stomach > Intestine(larva) > to lungs Coughed up, swallowed, return to intestine(mature to adult) • Eggs exit through feces

Tremors movie trailer http: //www. youtube. com/watch? v=li. Jf. Zv. X di. TE

Ascaris dissection http: //www. youtube. com/watch? v=a 7 RAo. J_2 W 5 ghttp: //www. youtube. com/watch? v=a 7 RA o. J_2 W 5 g