1) Platyhelminthes are a phylum of flatworms that are mostly parasitic and infect humans. They have bilateral symmetry, are flattened, and have three body tissue layers. 2) They have a digestive system with only a mouth and absorb nutrients through their skin. They reproduce sexually or asexually and have complex life cycles involving multiple hosts for parasitic species. 3) They circulate oxygen and nutrients through a closed circulatory system with vessels and can be found in aquatic and moist environments, infecting over 200 million people annually.

1. Platyhelminthes
Lauren Wagner and Madison Page
5-19-09
3rd
Period
Tapeworm
Hymenolepis diminuta
Fluke
Megaptera Novaeangliae

2. Classification
• Trematoda- parasitic; 12,000 species; various suckers; infect 200 million people a
year; 4 hosts.
• Cestada- 3,500 species; parasitic; mouth no gut; live anywhere with vertebrates.
• Turbellaria- aquatic; move with cilia; asexual reproduction (fission)
• Mongenera- 1 host in life; endoparasitic; free swimming

3. Body
• Bilateral symmetry.
• Flattened
• Ribboned shape
• 3layers of body tissues with organs.
• Blind gut- mouth no anus
• The protonephndral excretory organs which replace the anus
• No skeleton
• Nervous system of longitudinal fibers
• Unblinkable eyespots

4. Reproduction
• Eggs pass out with the primary host's feces and eventually contaminate water, where
they are ingested by snails (the first intermediate host).
• Eggs burrow into the digestive system.
• Sporocyst forms a redia asexually.
• It then leaves the snail and finds a fish host. It then affects the fish.
• Most species of flatworms reproduce either sexually or asexually

5. Digestive System
Flatworms absorb nutrients through their skin and excrete
wastes using specialized "flame cells."
There is only a mouth opening.
The mouth eliminates food.

6. Circulatory System
• Transport oxygen, nutrients, and wastes through the body via a closed circulatory
system.
• Blood travels from the anterior to the posterior through a ventral blood vessel and
then forward through a dorsal vessel.
• Five pairs of tubes, the aortic arches, link the major vessels near the anterior.
• Smaller vessels branch into each segment of the body.
• Contractions of the ventral vessel force blood through the body.

7. Respiratory System
Earthworms have no gills or other respiratory organs.
Oxygen and carbon dioxide diffuse directly across only moist skin.
(mucus and a thin cuticle also help keep the earthworm’s skin moist.)

8. Environment
• Mainly found in aquatic areas.
• Moist areas.
• Marine, freshwater areas.

9. Human Interactions
• Over half of all known flatworm species are parasitic, Schistosomiasis, caused by
Infection of humans by the broad fish tapeworm Diphyllobothrium latum occasionally
causes vitamin B12 deficiency.
• Platyhelminth parasites to humans with organic farming.
• The popularity of raw or lightly-cooked foods, and imports of meat, sea food and
salad vegetables from high-risk areas.

10. Unique Features
• Can be 50 meters long.
• Need symbiotic relationships to survive fatty acids.
• Well developed nervous system.

11. Pictures

12. Bibliography
Google. May 19th
, 2009.
http://images.google.com/images?hl=en&q=platyhelminthes&gbv=2&aq=f&oq=
Platyhelminthes. May 19th
, 2009.
http://zipcodezoo.com/Key/Animalia/Platyhelminthes_Phylum.asp
Platyhelminthes. May 19th
, 2009.
http://www.discoverlife.org/20/q?search=Platyhelminthes
Angelfire. May 19th, 2009.
http://www.angelfire.com/ut/biocheat/PlatyhelminthesNemat.html
Platyhelminthes. May 19th
2009.
http://faculty.pnc.edu/jcamp/parasit/flatworm.html

13. Platyhelminthes. May 19th
, 2009.
http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm
Phylum Platyhelminthes. May19th, 2009.
http://io.uwinnipeg.ca/~simmons/lb6pg6.htm
Platyhelminthes. May 19th
, 2009.
http://www.bumblebee.org/invertebrates/PLATYHELMITHES.htm
Holt, Rinehart and Winston. Animals: Holt Science and Technology. Time Warning
Company, 2000.
Tapeworms. May 21st
, 2009.
http://animals.jrank.org/pages/1532/Tapeworms-Cestoda.html

14. Trematoda. May 21st
, 2009.
http://www. answers.com/topic/trematoda
What Are Tapeworms. May 21st
, 2009.
http://www.wisegeek.com/what-are-flatworms.htm
May 21st
, 2009.
http://images.google.com/images?hl=en&um=1&sa=1&q=tapeworm&aq=f&oq=