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Platyhelminthes
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- 5. Phylum Platyhelminthes • Dividedinto two major groups: • Free-living (Planaria) • Parasitic (Tapeworm) Planaria Tapeworm (Taenia)
- 6. Flatworms • Head atthe front of the body with nerve centers. • No locomotive organs • Range in size – Some microscopic free-living forms – Parasitic forms over 20 meters long • Show many advances over Cnidaria
- 7. General Characteristics – Bilateralsymmetry – the most primitive bilateral animals – Tissue-organ level of organization – Flattened body shape »Dorso-ventrally Planaria Tapeworm (Taenia) Fluke
- 8. Planaria (class Turbellaria) • Typicalflatworms • 5-25 mm in length • Freshwater organisms – Streams and ponds – Beneath rocks, leaves, logs, etc. • Planaria are carnivores – Smaller animals – Dead organisms
- 9. Internal Structure ofa Planarian • Simple digestive system – Mouth • Pharynx – tube that can be extended through the mouth – Gastrovascular cavity • With a primitive intestine • Extracellular and intracellular digestion (cells lining intestine)
- 10. Reproduction in Planaria •Asexual Reproduction – Fragmentation. Head separates and forms tails. – Unbelievable potential for regeneration!! – Tails CAN regenerate heads!!
- 11. Reproduction in Planaria •Sexual Reproduction – Hermaphrodites . . . Again! – REMEMBER: self-fertilization does not occur – Fertilization is INTERNAL
- 12. Tapeworms (parasites) • Specializedadaptations for parasitic lifestyle – Thick cuticle to protect against digestive enzymes – No mouth (they absorb nutrients through all the body) – Structures to allow parasite to attach to host Tapeworm
- 13. Tapeworms Scolex (to anchor theintestine) Suckers Hooks
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- 15. Reproduction • Sexual (Possibleself- ferlilization) • Each square making up the body is a reproductive sac – > 100,000 fertilized eggs – Each square will eventually break off and is released in the feces of the host – Capsule surrounding larva is digestable, allowing the infection of a new host Proglottids
- 17. Platyhelminthes: Advances over cnidarians: •Bilateral symmetry • Cephalization • Internal fertilization • Parasitism
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- 20. Nematodes • Cylindrical wormswith no segments • Most of them are free-living but some are parasitic and responsible for many diseases. (Pinworm, anisakis, trichina) • No respiratory system.
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- 22. Mouth, anus, excretoryand nervous system and sexual reproduction.
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- 25. Características • Cylindrical segmented worms(metameres) • Earthworms and leeches. • Cutaneous respiration in terrestrial and branchial respiration in aquatic. • Closed circulatory system.
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- 27. Sexual reproduction (mostof them hermaphrodites) Clitellium functions Feed on remaininsgs of animals and plants Earthworms
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- 29. Leeches • Most ofthem freshwater • Feed on blood
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