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=dy4cQO
N7-JU&list=PLBA01CF012057626A
Phylum Nematoda
(roundworms)
• Pseudocoelom (false cavity): located
between endoderm and mesoderm
• Fluid filled
• O2, CO2, 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=liJfZvX
diTE
Ascaris dissection
http://www.youtube.com/watch?v=a7RAoJ_2
W5ghttp://www.youtube.com/watch?v=a7RA
oJ_2W5g