Which of the following is an example of excretion rather than egestion?
- A. The passing of undigested cellulose in faeces
- B. The loss of dead cells from the surface of the skin
- C. The removal of hair when it is cut
- D. The removal of carbon dioxide by the lungs
Explanation
Excretion is the removal of the waste products of the body's own metabolism, and carbon dioxide is made by respiration inside every cell, so the lungs are excretory organs. Faeces consist largely of material that was never absorbed into the cells at all, so removing them is egestion. This distinction is a standard exam point and turns on whether the substance was ever part of the body's metabolism.
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