1. Diversity of Life – Animals (flatworms, tapeworms)
PLATYHELMINTHES
(flatworms, tapeworms)

2. A Phylogeny of the Animal Phyla
Porifera
No true tissues
Cnidaria
radial symmetry
diploblastic
Ctenophora
Platyhelminthes
Acoelomates
Rotifera
Pseudocoelomates
Nematoda
Nemertea
Mollusca
Protostomes
true tissues
Annellida
Arthropoda
Bilateral symmetry
triploblastic
Bryozoa
Lophophorate phyla
Body cavity
Phoronida
Coelomates
Brachiopoda
Echinodermata
Chordata
Deuterostomes

3. Platyhelminthes - flatworms
Description
Animals that are
• triploblastic
• no body cavity(aceolomate)
• central nervous system
• bilateral symmetry

4. Platyhelminthes - flatworms
Free living flatworms
Tapeworms
Flukes

5. Tissue Layers
There can be two
or three
Ectoderm
Mesoderm
Endoderm
Diploblastic
Triploblastic

6. 3. Body Cavities - There are three different kinds
Coelomate - the coelom is lined on both sides with mesoderm
Pseudocoelomate - the coelom (= pseudocoelom) is lined on one side with mesoderm
Acoelomate - there is no body cavity between the digestive tract and body wall

7. Platyhelminthes - flatworms
Basic Structure - body plan
Acoelomate!!
mesoderm
endoderm
ectoderm

8. Platyhelminthes - flatworms
Basic Structure - a few improvements
Excretion

9. Platyhelminthes - flatworms
Basic Structure - a few improvements
Digestion
-digestion begins in the pharynx and nutrients are absorbed in the gastrovascular cavity

10. Platyhelminthes - flatworms
Basic Structure - a few improvements
Nervous system
Eyespots

11. Platyhelminthes - flatworms
Basic Structure - a few improvements
Nervous system
Cephalization

12. Platyhelminthes - Classification
Turbellaria - free living flatworms
-mostly marine, predators and scavengers

13. Platyhelminthes - Classification
2. Trematoda - flukes - vertebrate parasites

14. Platyhelminthes - Classification
2. Trematoda - flukes

15. Platyhelminthes - Classification
3. Cestoda (= Cestoidea) - tapeworms - vertebrate parasites

16. Platyhelminthes - Classification
3. Cestoda (= Cestoidea) - tapeworms - vertebrate parasites
Sucker discs
Hooks- for attachment
to host’s intestine
Scolex

17. Platyhelminthes - Classification
3. Cestoda (= Cestoidea) - tapeworms - vertebrate parasites
proglottid

18. Platyhelminthes - Classification
3. Cestoda - tapeworms- Beef tapeworm- Life cycle
Mature adult
in human intestine
Larvae release
in sewage
Juveniles
encyst in
cow muscle

19. Platyhelminthes - Classification
3. Cestoidea - tapeworms- Beef tapeworm- Life cycle

20. Platyhelminthes - Classification
3. Cestoda - tapeworms- Beef tapeworm- Life cycle
Mature adult
in human intestine
Larvae release
in sewage
Juveniles
encyst in
cow muscle

21. Symmetry
Body
Cavity
Skeletal
Digestive
Excretory
Nervous
Reproductive
Porifera
None
Spicules in mesohyl
Phagocytosis
Amoebocytes
Hermaphrodites
Asexual
Cnidaria
Radial
None – stiffened mesoglea
Nutritive muscle cells
Nerve net
Specialized zooids or asexual
Platyhelminthes
Bilateral
(acoelo-mate)
Incomplete
Flame cells
Cephalized
CNS
Hermaophrodite