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Body Plan
Transport within the Body
  • Digestive juices are spilled onto prey, the pharynx then sucks small pieces of food into the gastrovascular cavity
  • digestion is completed within the cells lining the cavity, each branched for increased amount of surface area and distribution throughout the organism.
(See gas exchange and waste disposal.)
Gas Exchange
Method of Waste Disposal
Nervous System
Important Distinguishing Feature
Lacks organs specialized for gas exchange and circulation.
Nitrogenous waste as ammonia diffuses from cells into the water because the flat shape makes the cells near the surrounding water. Undigested waste is also egested through the mouth. These organisms also have an excretory apparatus to maintain osmotic balance between the animal and its surroundings by flame cells (ciliated cells that waft fluid through branched ducts opening to the outside.)
Planaria has eye spots that detect light and lateral flaps for smell. The main sensory apparatus is the ganglia near the end of the worm, which is a dense cluster of nerve cells. It can modify responses to stimuli it recieves. Two longitudinal nerve cords run the length of the flatworms body.
Is hermaphroditic and can reproduce asexually through regeneration or fragmentation or sexually reproduce by cross-fertilization.
Produces the embryonic mesoderm, a third germ layer that allows for complex organs and true muscle tissue.