Reaction of Planaria to Stimuli
Salt Hot Water Chicken Liver Light
Moved Away Moved Away Moved Toward Moved Away
Juan and Carol were studying invertebrates in biology. They knew that segmented or earth worms preferred a dark, moist habitat.
During this lab, they would be investigating the responses of organisms called planaria or Dugesia tigrina. These were simple
flatworms that still had a one-way digestive system and a very simple nervous system. Juan and Carol placed the planaria in a petri
dish containing cool, distilled water that was partially covered with black paper. They shined a light on the dish. Next, they removed
the paper and placed a small amount of chicken liver at one end of the dish. They added a few large salt crystals to the water. Finally,
they added drops of hot water to the cool water in the petri dish. Their results can be seen in the data table. According to their
experiment, all BUT one conclusion is valid.
Planaria are a fresh-water organism only.
Planaria are consumers and may be carnivores,
Planaria have specialized cells to detect light intensity
Planaria have specialized cells that detect temperature change.