The general character of platyhelminthis are as follows :
1. Habit and habitat : They are moatly parasitic which live in the blood, intestine and liver of human. Some like planaria are freeliving found in freshwater, pond seawater and damp places on land. Parasitic form have suckers or hooks or other connective device for the attachment on the host.
2. Level of organization : Tapeworms are the first metozoan group having developed body organs.
3. Symmetry : They are radiaaly symmetrical and triploblastic animals.
4. Coelom : They are acoelomate animals. The space betwwen the body wall and internal organ are filled with parenchyma.
5. Respiratory organs are absent in them and they perform aerobic type of respiration. Their exretory organ is called
flame cell or protonephridia.
6. Reproduction : They reproduce sexally but some of the freshwater turbellarians reproduce asexually by regeneration and fission.
The classification of phyllum platyhelminthes are as follows :
1. Turbellarian
 |
| Planaria |
a. They are in free-living aquatic form found in fresh water stream, pond, seawater and moist places.
b. They have unsegmeted body.
c. Sucker and hooks are absent in them.
d. Their lifecycle is simple and regeneration is common in them.
eg : bipalium, planaria etc
2. Trematoda
 |
Liver-fluke
|
a. The are exclusively parasite (ecto or endo)
b. They have usually elongated and unsegmented body.
c. Sucker are present in them but hooks and spines are absent in them.
d. Their life cycle is complex. They require one or more host to complete their lifecycle.
eg : Fasciola hepatica (liver fluke) , Schistosome (blood fluke) etc
3. Cestoda
a. They are exlusively endoparasite living in the small intestine of vertebrate animals.
b. They have segmented body like tape.
c. Sucker and hooks are present in them for the attacment in the host.
d. Their life cycle is also complex. They also require one or more host.
eg : Taenia solenia (tapeworm) etc
