Planaria are flatworms that live in usually, quiet ponds or bodies of water. Planaria, like all flatworms, live in the Kingdom Animalia. Inside a petri dish, the Planaria move to areas which contain the least amount of light. If a flashlight is shunned on a Planaria, it attempts to move out of the light. Planaria do not have lungs or gills, rather they obtain their oxygen from simple diffusion over its flat body. Planaria have been found to have many stem cells in their body. Stem cells are cells that are not specialized. Neoblasts, pluripotent adult stem cells, help the Planaria regenerate quickly. The detailed study of mouse stem cells led to the discovery, in 1998, that stem cells derive from human embryos and grow the cells.
