Phylum PlatyhelminthesPhylum Platyhelminthes

Flatworms

CharacteristicsCharacteristicsBilaterally symmetrical - Mirrored right and left

sidesTripoblastic - Bodies have 3 cell layers

– Epiderm / Ectoderm (outside)– Mesoderm (middle)– Endoderm (inside)

Organs – Reproductive, Musculature, ExcretoryCephalization – concentration of nervous tissue at

anterior.Pharynx – Combined mouth and anus

ClassificationClassification1. Class Turbellaria – “Free-living” flatworms

Ex. Planaria Most, some fresh water, some terrestrial.

Marine planaria

Freshwater planariaParasitic Terrestrial

planaria

2. Class Trematoda - Parasitic flukes

Ex. Liver Flukes, Blood Flukes

Sheep Liver Fluke

Human Blood Fluke

3. Class Cestoda -

Ex. Parasitic Tapeworms

Tapeworm AnatomyTapeworm Anatomy

Scolex - Head Proglottid - Segment

Tapeworm Anatomy (Cont’d)Tapeworm Anatomy (Cont’d)

Tapeworm Lifecycle