Planarian: A Flatworm SWBAT define bilateral symmetry; define free living; describe the nervous system of the planarian; describe the processes of digestion and excretion in the planarian

Planarian  Bilateral symmetry Two equal sides to the animal. One side is a mirror image of the other.  The planarian is only 2 cm long. Draw a line estimating how big that would be, then get a ruler and see how close you were.

Planarian  What phylum do flatworms belong to? Platyhelminthes  flatworms  Free-living An animal that is not a parasite (which needs a host), it lives on its own.  Parasites Fleas, tapeworms

Nervous System  Neurons Long, thin nerve cells that are found throughout the body. They carry impulses from one point to another.  Nerve Collection of neurons wrapped in a protective coating  Ganglion Simple brain, coordination center – controls the nervous system

Nervous System  Describe how the ganglion, nerves and neurons work together in the planarian. The nerves interpret a touch and send the impulse to the ganglion. The ganglion then sends a response back through the nerves that creates a response to the stimulus.

Nervous System  Stimulus Something an organism can sense

Digestive and Excretory Systems  Describe how the process of digestion and excretion occur in a planarian. The pharynx shoots out of the mouth and sucks food to the intestine, where enzymes secreted by the gastroderm begin to digest it. The cells then absorb the food and finish breaking it down by cellular digestion. Non-digestible material is pushed back out through the mouth. Waste is excreted through tiny tubes at the end of which are flame cells, where cilia beat the end and move waste and water through the tubes.

Other Flatworms  Tapeworms  Flukes  Marine flatworms