The document discusses the phylum Platyhelminthes, or flatworms. It notes that flatworms have a triploblastic body plan with three cell layers and are bilaterally symmetrical. The phylum contains four classes - Turbellaria, Cestoda, Trematoda, and Monogenea. Turbellaria includes planaria, while Cestoda and Trematoda include tapeworms and flukes respectively. Flatworms range in size from millimeters to meters and have an incomplete digestive system with one opening. They can reproduce asexually through fission or sexually. Removal of parasitic flatworms requires careful treatment.

1. Phylum Platyhelminthes
“Flat Worms”
By
Mrs. Farkhandah Shareef

2. Triploblastic
Having a body derived from three embryonic
cell layers (ectoderm, mesoderm, and
endoderm), as in all multicellular animals
except sponges and coelenterates.

3. Triploblastic Acoelomate Body Plana:
EVOLUTIONARY PERSPECTIVE
Members of the phyla are:
(a) Phylum Platyhelminthes:
(b) Phylum Nemertea:
(c) Phylum Gastrotricha:

4. Platyhelminthes
 Platy = flat
 Helminthes = worm
 Flat Worms

5. There are four classes of flatworms, three of which
are important to us…

6. Platyhelminthes
 Class: Turbellaria – planaria
 Class: Cestoda – tapeworms
 Class: Trematoda – flukes

7. Size range:
 Their size ranges from few millimeters (10
mm in case of planaria) to several meters
(tapeworm).
 Digestive system
 Excretory system

8. There are two types of reproduction;
 asexual reproduction
 sexual reproduction
Reproductive System
and
Reproduction

9. Example of Platyhelminthes Animals

10. Characteristics
1. Triploblastic

11. a) Ectoderm (epidermis)
b) Mesoderm
c) Endoderm
 Flatworms 3 cell layers:

12.  2. Linear nervous system with a ganglion (brain)

13. Characteristics
3. Dorsoventrally flat, bilaterally symmetrical body

14. Characteristics
4. Cephalization – the development of an anterior end

15. Characteristics
5. Incomplete digestive system (one opening)
6. An excretory system for removing cellular wastes

16. Adaptations from parasitic mode of life
1. Epidermis is absent
2. Developed adhesive organs
3. Degeneration of muscular system and
nervous system.
4. Digestive system has become simplified
5. Reproductive systems are complicated
6. Complexity of life cycle

17. Infestation:

18. Disinfestation:
 difficult to remove it completely.
 care should be taken
 Complete removal is necessary
 give anema to the patient