Excretion

Excretion MDCAT MCQs with answers

14 past paper MCQs on Excretion, from the Homeostasis unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.Which of the following organisms eliminate nitrogenous waste mainly in the form of uric acid? (UHS MDCAT 2025)

  1. Freshwater Fish
  2. Amphibians
  3. Birds
  4. Mammals
Show answer

Correct answer: (c) Birds

Birds and reptiles are uricotelic, which saves the water an egg cannot spare.

2.Which nitrogenous waste has the lowest solubility in water? (KMU MDCAT 2025)

  1. Urea
  2. Ammonia
  3. Uric acid
  4. Nitrite
Show answer

Correct answer: (c) Uric acid

Uric acid is almost insoluble, which is why it can be excreted as a paste with almost no water.

3.By nature, human excretory system is: (KMU MDCAT 2025)

  1. Ammonotelic
  2. Uricotelic
  3. Ureotelic
  4. Aminotelic
Show answer

Correct answer: (c) Ureotelic

Humans convert their ammonia to urea in the liver, so they are ureotelic.

4.Which one of the following is the most common nitrogenous waste excreted in urine of a healthy human? (SIBA MDCAT 2025)

  1. Ammonia
  2. Urea
  3. Uric Acid
  4. Creatinine
Show answer

Correct answer: (b) Urea

Urea is the chief nitrogenous waste of human urine.

5.Which class of animals excrete ammonia as their primary nitrogenous waste? (SIBA MDCAT 2025)

  1. Uricotelic
  2. Urotelic
  3. Ammonotelic
  4. Ureotelic
Show answer

Correct answer: (c) Ammonotelic

Animals that excrete ammonia directly, chiefly aquatic ones, are ammonotelic.

6.Which one of the following organism is uricotolic with reference to excretion of nitrogenous compound? (SZABMU MDCAT 2025)

  1. Human
  2. freshwater Fish
  3. Snake
  4. Frog
Show answer

Correct answer: (c) Snake

Reptiles and birds excrete uric acid, which needs almost no water to void.

7.Ureotelism (removal of nitrogenous waste in the form of urea) is an adaptation to the: (SZABMU MDCAT 2025)

  1. cold weather
  2. less availability of water
  3. flooded environmental conditions
  4. food shortage
Show answer

Correct answer: (b) less availability of water

Urea is far less toxic than ammonia, so it can be concentrated and less water is spent on it.

8.Which of the following fish drink large amount of seawater and excrete concentrated urine resulting in maximum salt excretion and minimal water loss? (PMC MDCAT 2022)

  1. Hagfish
  2. Freshwater fish
  3. Bonyfish
  4. Cartilaginous fishes
Show answer

Correct answer: (c) Bonyfish

A bony fish in the sea is losing water, so it drinks and voids the salt in a small volume of urine.

9.As an excretory organ, liver: (PMC MDCAT 2020)

  1. Detoxifies many chemical poisons
  2. Breaks down ammonia for excretion by the kidneys
  3. Produces urea and uric acids from the nitrogen of amino acids
  4. All of the above
Show answer

Correct answer: (d) All of the above

The liver detoxifies, deaminates the amino acids and makes the urea the kidney then excretes.

10.The main nitrogenous excretory product of humans is: (UHS MDCAT 2019)

  1. Ammonia
  2. Urea
  3. Ammonium
  4. Uric acid
Show answer

Correct answer: (b) Urea

Humans convert their ammonia to urea in the liver.

11.The route of urine excretion from kidney to outside of body is: (UHS MDCAT 2019)

  1. Kidney -> ureter -> urinary bladder -> urethra
  2. Urinary bladder -> kidney -> ureter -> urethra
  3. Kidney -> urethra -> urinary bladder -> ureter
  4. Kidney -> ureter -> urethra -> urinary bladder
Show answer

Correct answer: (a) Kidney -> ureter -> urinary bladder -> urethra

Urine passes from the kidney down the ureter to the bladder and out through the urethra.

12.Urea cycle is the detoxification of: (UHS MDCAT 2018)

  1. Creatinine
  2. Amino acids
  3. Carbon dioxide
  4. Ammonia
Show answer

Correct answer: (d) Ammonia

The liver turns the toxic ammonia of deamination into urea.

13.Highly toxic nitrogenous excretory product is: (UHS MDCAT 2016)

  1. CO2
  2. Uric Acid
  3. Urea
  4. Ammonia
Show answer

Correct answer: (d) Ammonia

Ammonia is very toxic, which is why it must be either diluted greatly or converted to urea.

14.The removal metabolic waste from the blood is called: (UHS MDCAT 2016)

  1. Thermoregulation
  2. Osmoregulation
  3. Kidney Failure
  4. Excretion
Show answer

Correct answer: (d) Excretion

Removing the waste of metabolism from the blood is excretion.

More in Homeostasis