1. Kingdom Animalia: Phylum Platyhelminthes: The Flatworms
Biology 11
Kingdom Animalia:
Phylum Platyhelminthes:
The Flatworms

2. Phylum Platyhelminthes Objectives
Advances over Cnidarians
Body plan (systems and structures)
3 classes and example animals
Parasitic worms (enter, live, hosts, effects)

3. The Acoelomates
The acoelomates advanced animal evolution in two significant ways: 1. Bilateral symmetry 2. Triploblastic Are still primitive because lack a body cavity

4. Phylum Platyhelminthes
The Flatworms
Characteristics and Advances
Still have incomplete digestive system with a gastrovascular cavity (just like Cnidarians) but…
They are the first phylum with an excretory system made of “flame cells” and pores (so mouth is no longer anus as well!)

5. Phylum Platyhelminthes
3. Have a “Nerve Ladder” type of nervous system 4. Reproduce mostly sexually but have excellent powers of regeneration which can be a form of asexual reproduction 5. Cephalization begins with a “brain” and sense organs appearing anteriorly in a head

7. Phylum Platyhelminthes
Class Turbellaria
Includes the Planaria a fresh water flatworm
Also includes many marine varieties
Planaria sp.

8. Phylum Platyhelminthes
Class Trematoda
Includes the parasitic flukes
Include liver, blood, lung, heart, and intestinal flukes
Many have intermediate hosts like this liver fluke (i.e. sheep, cow, fish etc)
Fasciola hepatica

9. Fasciola hepatica (Liver Fluke)

11. Fasciola hepatica Life Cycle

12. Phylum Platyhelminthes
Class Cestoidea: the tapeworms
Classical endoparasite appears degenerative but actually highly evolved to its habitat
Human tapeworms can grow up to 20 m long!

13. Tape worm Anatomy

14. Tape worm Life Cycle