Question

The removal of wastes from the body is known as:
A. Excretion
B. Digestion
C. Extraction
D. Ingestion

Answer 1

Hint: Our body needs to get rid of certain substances like carbon dioxide, water, and other harmful substances. Like our lungs excrete carbon dioxide as we breathe out, our kidneys filter out harmful substances to produce urine.

Complete answer: Excretion is a process by which our body eliminates metabolic wastes. It is primarily carried out by the kidneys, lungs and skin in vertebrates. Excretion is a very essential process in all forms of life. Waste products are directly discharged through the surface of the cell in unicellular organisms and in mammals, urine is expelled through the urethra. During various life activities like cellular respiration, several chemical reactions occur which contribute to metabolism. These chemical reactions produce wastes like salts, urea, uric acid, carbon dioxide and water. Keeping these wastes in the body beyond a level is harmful to the body. So, excretory organs remove these wastes from the body and maintain the physiology of the body. In animals, main excretory products are ammonia (ammonotelic), urea (ureotelic), uric acid (uricotelic), carbon dioxide, creatine and guanine (Arachnida). In renal excretion, the kidney and liver clear many substances from the blood and these substances are excreted out from the body through the process of excretion. Birds excrete nitrogenous wastes as uric acid in the form of a thick paste and aquatic animals usually excrete ammonia directly into the environment.
Hence, the correct answer is option A.

Note: In insects, a system involving Malpighian tubules is utilized to excrete metabolic wastes. Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the intestines.