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

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

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

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!)

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

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

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

Fasciola hepatica (Liver Fluke)

Fasciola hepatica Life Cycle

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!

Tape worm Anatomy

Tape worm Life Cycle