1. FLATWORMS
Belong to the KINDGOM ANIMALIA
PHYLUM PLATYHELMINTHES

2. Characteristics Three germ layers (endoderm, ectoderm, mesoderm)
Bilateral symmetry
Cephalization (has a head)
COELOM = fluid filled body cavity Acoelomates = without coelom

3. FORM AND FUNCTION FEEDING
Free-living - carnivores or scavengers; they have a digestive cavity, mouth and pharynx
Parasites – feed on blood, tissues or pieces of cells from within a HOST
Most do not have a complete digestive system because they absorb material directly from host

4. Respiration, Circulation, and Excretion
Thin bodies allow for materials to diffuse (respiration, excretion, etc)
Flame Cell – specialized cells that remove excess water

5. Response
Ganglia – group of nerve cells that control the body (like a brain)
Eyespot – group of cells that can detect light (like an eye)

6. Movement Flatworms move in 2 ways
Cilia helps them glide through the water
Muscle cells help them twist and turn

7. Reproduction
Sexual Reproduction – most flatworms are hermaphrodites (have both male and female sex organs)
Asexual Reproduction by fission – flatworms can split in two and regenerate

8. Groups of Flatworms CLASS TURBELLARIA - free living flatworms
- live in fresh or marine water
- ex. Planarian

9. Dugesia lives in freshwater, mostly a scavenger but can also feed on protists

10. Planarians are hermaphrodites
They can also regenerate body parts and will sometimes split in half to reproduce (FISSION)

11. ANATOMY OF A PLANARIAN

12. Brain (ganglia) - planarian can process information about their environment
Pharynx - used for suckling food in (the mouth is at the end of the pharynx)
Eyespot - simple eye, can detect light
Flame cells - located along the lateral edges, used for excretion
Intestine - digestion (does not have an anus)

13. Class Trematoda = parasitic flatworms
a.k.a “flukes” live in mouth, skin, or gills of host
Primary host = the host in which a parasite reproduces sexually
Intermediate host = the host in which asexual reproduction occurs

14. Schistosoma mansoni - multiple host:
Primary host = human
Intermediate host = snail
Causes Schistosomiasis -in humans; decays lungs liver, spleen, or intestines, occurs in tropical areas with poor sanitation/sewage.

15. Class Cestoda =tapeworms
Long, flat, parasitic
Live in intestines

16. Scolex = a structure that contains suckers and/or hooks
Proglottids = body segments of the tapeworm

17. Each mature proglottid is a hermaphrodite
Testes produce sperm, fertilize the eggs to produce a zygote
Zygotes are passed out through the feces.

18. Sometimes, a dormant, protective cyst is formed in the intermediate host muscles
****This is why you should never eat incompletely cooked meat.

19. Adapted from www.thebiologycorner.com