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Phylum Platyhelminthes

Phylum Platyhelminthes. Name? From 2 Greek words: ‘ platy’ meaning flat and ‘ helminth ’ meaning worm. Characteristics:. Have tissues and internal organs Have 3 embryonic germ layers – endoderm, mesoderm a nd ectoderm Bilateral symmetry Cephalization Acoelomates – No body cavity persent.

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Phylum Platyhelminthes

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  1. Phylum Platyhelminthes Name? From 2 Greek words: ‘platy’ meaning flat and ‘helminth’ meaning worm Characteristics: • Have tissues and internal organs • Have 3 embryonic germ layers – endoderm, mesoderm • and ectoderm • Bilateral symmetry • Cephalization • Acoelomates – No body cavity persent

  2. 3 Main Groups or Classes: Turbellaria – Free living, most live in marine or Fresh water. Example: Planaria(Fresh water)

  3. Marine dwelling:

  4. Some live on the forest floor:

  5. 2. Class Trematoda (Flukes): Parasitic flatworms often living in the host’s internal organs. Some are ectoparasites on the host’s skin, mouth, gills, etc.

  6. Liver fluke in deer

  7. 3. Class: Cestoda Tapeworms – Long, flat parasitic worms adapted to life inside the intestines of their hosts.

  8. Characteristics: • Have tissues and internal organs • Have 3 embryonic germ layers – endoderm, mesoderm • and ectoderm • Bilateral symmetry • Cephalization • Acoelomates – No body cavity persent

  9. Specialized structures: • Free living flatworms: Ganglia (groups of nerve cells) • that control a nervous system – primitive ‘brain’. • Also have eyespots to • detect light with

  10. Free living flatworms have mouth with a pharynx that pumps food into the digestive cavity.

  11. Free living flatworms have muscle cells to aid in • movement • Some flatworms have flame cells that help them remove • excess water and also wastes like ammonia and urea • from the body. (Help with excretion)

  12. Parasitic worms such as tapeworm: • Head (scolex) contains several hooks or suckers that are used to attach to the intestinal wall of the host

  13. Mode of nutrition: Free living flatworms: Predators or scavengers – eat molluscs, protozoans, crustaceans, some live with algae that provide them with carbohydrates. Use pharynx to pump in food into the mouth. Have a digestive cavity or gut. Parasitic flatworms: Feed on blood, tissue or pieces of cells within the host’s body. Tapeworms have no digestive cavity – simply absorb nutrients that Are already in the host’s intestines.

  14. Movement: Free-living: Use cilia and muscle cells to glide, twist and turn. Reproduction: • Free living: Hermaphrodites and reproduce sexually. • Sperm are delivered between 2 flatworms. Eggs are • laid and hatch in a few weeks. • Also reproduce asexually through fission.

  15. Parasitic flatworms: They have complicated life cycles that can involve both sexual and asexual reproduction. http://science.jburroughs.org/mbahe/BioA/starranimations/chapter23/videos_animations/tapeworm.html

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