Kidney
internal organ in most animals, including vertebrates and some invertebrates
Does an organ donor need to be dead to donate a kidney?
The average human has two kidneys. Only one kidney is required to function as a healthy person. Living organ donors will sometimes donate their spare kidney to someone experiencing failure of both their kidneys.
How many kidneys does the average person have? How many kidneys does a person require to function? Is #1 the same as #2?