Which animals can regenerate lost body parts?
Worms can, and starfish too. If a salamander is being attacked,
then its tail falls off. That distracts the predator long enough
for the salamander to make a quick getaway. It can then regrow the
tail and eventually be good as new.
Animals like sponges and coral colonies naturally fragment and reproduce. Many species of annelids and flat worms reproduce by this method. The animal splits and the two parts remake lost organs and tissues. The splitting is not preceded by the development of the tissues to be lost. Prior to splitting, the animal may develop furrows at the zone of splitting. The headless fragment has to regenerate a complete head.
Usually a planaria regeneration experiment involves cutting the planaria into different parts. The head can be separated from the tail or the planaria can be cut lengthwise, etc. After cutting the planaria, it will be observed for few days noting how the organism regenerate its lost body parts. Read more on planaria regeneration on t he link provided below.
What general type of reagent might the body use to regenerate vitamin C that was lost in a cooked vegetable?
The liver is the only internal organ that can regenerate itself. In fact, you can lose up to 75 percent of your liver, and the remaining parts can regenerate itself into a whole liver again. Hepatocytes are the liver cells that are responsible for the liver's ability to regenerate; they act as stem cells that can re-form liver tissue.