Hydras are simple freshwater organisms found in temperate and tropical regions. They are especially interesting to biologists because they undergo morphallaxis when injured, regenerating new body parts to replace dead or damaged tissue. When a hydra is severed in two, for example, its segments reorganize to form two fully functional, independent hydras. Some evidence suggests that hydras are unique among animals in that they do not experience senescence, meaning they do not undergo what process? Discuss
Source: The Free Dictionary