1. Platyhelminthes

2. General Characteristics
flattened, bilaterally symmetrical
have no other body cavity than the digestive cavity (acoelomates)
platy = flat & helminthes = worms
Platyhelminthes were regarded as a primitive stage in the evolution of bilaterians soft and ciliated epidermis covered with cuticle and external suckers or hooks, or both
space between internal organ filled by loose parenchyma
well developed muscle layers
no skeletal, circulatory, or respiratory system

3. Classes of Platyhelminthes
Turbellaria-Planaria

4. Classes of Platyhelminthes
Cestoda-beef & pork tapeworms

5. Classes of Platyhelminthes
Monogenea-Diplozoon paradoxum

6. Classes of Platyhelminthes
Trematoda-Human Live Fluke

7. Body Plan Bilateral symmetry
have no other body cavity than the digestive cavity (acoelomates)
three germ layers (mesoderm, ectoderm, endoderm)
soft and ciliated epidermis covered with cuticle and external suckers or hooks, or both

8. Feeding General Turbellarians Cestoda Monogena and Trematoda
flat worms have one digestive opening that branches to all parts of the body
Turbellarians
use muscular pharynx and prey on smaller animals or feed on dead animals
Cestoda
block the intestines and rob nutrients from the human host
Monogena and Trematoda
use suckers for attaching to internal organs rely on the host for digestion

9. Respiration General Respiration occurs through diffusion
Mainly carnivorous and prey on small invertebrates
Also feed on remain of dead animal
All exchange is on a cellular level, by diffusion, which is why flatworms are flat. Nitrogenous waste mostly as ammonia, lost through diffusion. Endoparasitic forms often rely on anaerobic metabolism

10. Circulation General Circulation occurs through diffusion
Lack circulation system
Some species have gastrovascular system
Otherwise, all internal transport occurs by simple diffusion through and between cells of the small body.

11. Excretion General Excretion occurs through flame cells
Mouth: anterior end or mid-body on ventral surface
Lack an anus
 Excess water (and possibly wastes) enters the flame cell system and is propelled through the tubules toward the outside by the beating of the cilia (the "flame

12. Response General Higher temperature and starvation
Negatively affect size
Decrease the number of days that elapsed before egg laying began
More larvae at 21°C than at 30°C
Tangoreceptor: respond to touch
Minimal b/c no orientation to light or gravity
Light sensitive eyespots
Can adapt and modify

13. Response II Ocelli eyespots that detect light Gangalia
main sources of sensory input
Aurical
tasting chemicals
Have a cephalized nervous system
ventral nerve cord
head ganglion attached to nerve cords connected body
by transverse branches across the

14. Movement Turbellians Cestoda Monogenea and Trematoda
use cilia to move over a secreted slime tract
head slightly raised
Cestoda
absorb nutrients from host
no movement
Monogenea and Trematoda
parasitic worms rely on the host's circulation
suckers for attachment

15. Reproduction General Asexual reproduction Budding Binary fission
Regeneration
Sexual reproduction
Hermaphroditic
Occurs through the exchange of sperm
Internal fertilization
Cross fertilization

16. Reproduction II Turbellaria exchange of sperm Cestoda
proglottids: several ovaries and 1,000 distinct testes
Monogenea
make both sperm and eggs
Trematoda
gut and well-developed reproductive system

17. Works Cited
"Platyhelminthes." W. Fielding Rubel School of Business. Web. 21
"Platyhelminthes." Oracle ThinkQuest Library. Web. 21 Apr <
"Behavior and Reproduction." Monogeneas. Web. 21 Apr <

18. The End