Emily, Azaria, Chris Period 5 Platyhelminthes Emily, Azaria, Chris Period 5

General Description Phylum- Platyhelminthes contains flatworms Soft, unsegmented, & flat (no more than a few mm thick) Tissues (tripoblastic) & internal organ systems Simplest animals to have: 3 embryonic germ layers, bilateral symmetry, & cephalization Do not have coeloms (body cavity) Live in fresh or marine water Most of their oxygen through diffusion

Symmetry No body cavity- aceolomates Bilateral symmetry Gastrovascular cavity with one opening Some breath through skin

Feeding Parasites- enter body of other organisms, can absorb and consume what the host eats 80% are free living Turbellaria- carnivores (tiny aquatic invertebrates)

Circulation Flatworms take in oxygen and release carbon dioxide Flatworms don’t undergo cellular respiration Flatworms undergo diffusion to obtain the oxygen they need, and release carbon dioxide they don’t This is mostly the reason why they’re flat Central nervous system: the complex of nerve tissues that controls the activities of the body.

Excretion The digestive cavity has only one opening for both intake of food and the excretion of it As a result the food cannot be processed continuously Cilia help move foods to be digested and then excreted through their mouths Pharynx: the membrane-lined cavity behind the nose and mouth, connecting them to the esophagus. Flame cell: a specialized excretory cell- function like a kidney, removing waste materials.

Response They have ganglia Have a complex structure for detecting and responding to external stimuli Have eyespots that can detect changes in the amount of light in their environment Have specialized cells that detect external stimuli

Movement Free-living Uses cilia and muscle cells

Reproduction Most are hermaphrodites Reproduce sexually with internal fertilization Parasitic Commonly reproduce asexually by fission Can reproduce sexually

Respiration Gas exchange Uses diffusion

Classes of Platyhelminthes Trematoda Turbellaria Cestoda

Trematoda Parasites Infect animals and humans Specialized body (Parasitic life) Fasciola hepatica (Liver fluke)

Turbellaria Free living flatworms Most are aquatic Some are terrestrial Planaria

Cestoda Tape worms Intestinal parasites Proglottid: segment containing complete reproductive system Taenia solium (Pork tapeworm)

Works Cited https://www.shapeoflife.org/video/flatworms-first-hunter https://excreting101.weebly.com/platyhelminthes.html

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