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c. Platyhelminthes

c. Platyhelminthes. Jessica Calahorra 9B. Phylum Platyhelminthes. Turbellaria Monogenea Trematoda Cestoda. Turbellaria. Monogenea. Trematoda. Cestoda. Reason for Name. The name Platyhelminthes comes from two Greek words . Platy = flat Helminthes = worm.

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c. Platyhelminthes

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  1. c. Platyhelminthes Jessica Calahorra 9B

  2. PhylumPlatyhelminthes • Turbellaria • Monogenea • Trematoda • Cestoda Turbellaria Monogenea Trematoda Cestoda

  3. ReasonforName • ThenamePlatyhelminthes comes fromtwoGreekwords. • Platy = flat • Helminthes= worm

  4. SpeciesCurrentlyExisting • There are 20,000 species. • They are dividedintothefour sub-phylas.

  5. Characteristics • Nothingisknownfromtheirevolutionaryhistorybecausetheyhaveverysoftbodieswhich do not preserve well as fossils. • No internalcavity. • Somespeciesoccur in allmajorhabitats. • Parasiticspecies. • SacBody Plan: it has oneopeningwhichfunctions as a mouth and ananus. • 3 germlayers- ectoderm (outermostlayer), mesoderm (middlelayer) and endoderm (innermostlayer-digestivetrack) • Bilateral Symmetry • They are Hermaphrodites • It has a mouthbut no anus. • Asexual + Sexual Reproduction

  6. FirstFossil • ThefirstfossilappearedonEarthwas 40 millionyears ago. • Itwas a Turbellarianfossil.

  7. LifeCycle(Trematoda) • They are mainly parasites of vertebrates. • The males are shorter and fatter than the females, and have a ventral groove along their body, into which the female can fit. • The fertilized eggs break into the host’s bladder and pass out with the urine into the soil. • The worm hatches and enters the body of a snail. • In the snail’s body cavity, it grows into a large sac. It then hatches into a greater worm stage called the redia. • The redia has a mouth and an intestine and migrates to the snail’s digestive organ. • The redia develops into a tiny version of the adult, which drops out of the snail and goes into the water where it might enter a human body through the mouth or the skin. • Life Expectancy: 100-200 years

  8. DigestiveSystem • Itis a combination of digestive and excretionsystem. • Its a blindsystemsincethereisonlyoneopening. • Thefoodentersthemouth, whichgoestotheendodermallayerwichtakes place theabsorbtion and thedigestion of thefood. • Itisdigested in the gastrovascular cavity. • Any non-digestablefoodisspitoutthroughthemouth (vomit). • Platyhelminthesnormallyeatsoft coral, bryozoan and otherinvertebrates.

  9. Circulatory and RespirationSystem • Platyhelmintheslackcirculatory and respirationorgans, that’swhytheirbodies are so flat. • Theflat bodyallowsthemovement of oxygen and nutrientstoreachalltheparts of thebody. • Its a diffusionprocess. • Carbondioxideleavesthebodythroughthisprocess. Respirationoccursthroughdiffusion.

  10. SensorySystem • Thesensoryorgans are detectednearthe head. • Theydetectsight, touch, movement… • Italsosensesfood.

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