1) If waste materials are not sent out of the body from time to time they get accumulated in the body.
2) The accumulation of toxic wastes in the body harms an organism.
3) For an organism to lead a normal life, the toxic wastes being produced in its body must be removed from time to time.
4) If all the waste released is not sent out, the waste gets stagnated, produce toxins and poisons which pollute the body. They lead to death of the organism.
Excretory system is present in human body which discharge out the waste material time to time. Basically when cell in a body breaks down they produce various waste material like urea, uric acid and carbohydrates. Kidney is the excretory organ which eliminates urea, respiratory system eliminates carbon dioxide while digestive system eliminates waste material through feces. Any malfunctioning can cause serious problem like constipation, kidney failure. kidney stones.
Hope it helps.