Excretion in Animals Practice Questions
20 free Excretion in Animals practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is excretion in animals?
- A The process of taking in oxygen from air
- B The digestion of complex food in the gut
- C The movement of blood through the vessels
- D Removal of metabolic waste from the body
Correct answer: Removal of metabolic waste from the body
Excretion is the process by which animals remove metabolic wastes from their bodies. These wastes are produced during chemical reactions in cells and can be harmful if they accumulate.
Which of the following is a major nitrogenous waste in humans?
- A Glucose
- B Starch
- C Lactose
- D Urea
Correct answer: Urea
Urea is the main nitrogenous waste produced in humans from the breakdown of proteins. It is transported by blood to the kidneys and removed in urine.
Which organs are the main excretory organs in humans?
- A Lungs
- B Stomach
- C Small intestine
- D Kidneys
Correct answer: Kidneys
The kidneys are the main excretory organs in humans. They filter blood and remove wastes, excess salts, and extra water in the form of urine.
The structural and functional unit of the kidney is called the:
- A Neuron
- B Alveolus
- C Villus
- D Nephron
Correct answer: Nephron
The nephron is the basic filtering unit of the kidney. Each nephron filters blood and helps form urine through filtration, reabsorption, and secretion.
Which blood vessel brings blood to the kidney for filtration?
- A Renal vein
- B Pulmonary artery
- C Renal artery
- D Coronary vein
Correct answer: Renal artery
The renal artery carries blood containing wastes to the kidneys. This blood is filtered in the kidneys before returning through the renal vein.
Which tube carries urine from the kidney to the urinary bladder?
- A Urethra
- B Oesophagus
- C Trachea
- D Ureter
Correct answer: Ureter
The ureter carries urine from each kidney to the urinary bladder. The bladder stores urine temporarily before it is expelled from the body.
Which organ stores urine before it is passed out of the body?
- A Adrenal gland
- B Gallbladder
- C Pancreas
- D Urinary bladder
Correct answer: Urinary bladder
The urinary bladder is a muscular sac that stores urine. When it becomes full, urine is released through the urethra.
Which tube carries urine from the urinary bladder to the outside of the body?
- A Ureter
- B Renal artery
- C Bile duct
- D Urethra
Correct answer: Urethra
The urethra carries urine from the urinary bladder to the outside of the body. It is the final passageway in the urinary system.
Which excretory product is mainly removed from the body by the lungs?
- A Urea
- B Uric acid
- C Excess salt only
- D Carbon dioxide
Correct answer: Carbon dioxide
The lungs remove carbon dioxide, which is produced during cellular respiration. They also release some water vapor during exhalation.
Which organ converts toxic ammonia into less toxic urea in humans?
- A Heart
- B Brain
- C Spleen
- D Liver
Correct answer: Liver
The liver converts highly toxic ammonia into urea through the urea cycle. Urea is then carried by blood to the kidneys for removal.
Which of the following animals mainly excretes ammonia?
- A Sea bird
- B Desert lizard
- C Freshwater fish
- D Adult human
Correct answer: Freshwater fish
Many aquatic animals such as freshwater fish excrete ammonia because it can easily diffuse into surrounding water. Ammonia is very toxic but can be diluted quickly in water.
Birds and reptiles mainly excrete nitrogenous waste in the form of:
- A Ammonia
- B Urea
- C Uric acid
- D Carbon dioxide
Correct answer: Uric acid
Birds and reptiles usually excrete uric acid, which requires very little water for removal. This adaptation helps conserve water, especially in land-dwelling animals.
Why do mammals such as humans excrete urea instead of ammonia?
- A Urea is used directly for photosynthesis
- B Urea cannot dissolve in water
- C Urea is less toxic than ammonia
- D Urea is a type of blood cell
Correct answer: Urea is less toxic than ammonia
Ammonia is highly toxic and must be removed quickly or converted into a safer compound. Mammals convert ammonia into urea, which is less toxic and can be transported in blood.
Which process in the nephron allows useful substances like glucose and water to return to the blood?
- A Photosynthesis
- B Pollination
- C Reabsorption
- D Clotting
Correct answer: Reabsorption
Reabsorption occurs in the nephron when useful substances are taken back into the blood. This helps prevent loss of important materials such as glucose, salts, and water.
Which of the following is normally absent in the urine of a healthy person?
- A Urea
- B Water
- C Glucose
- D Salts
Correct answer: Glucose
Glucose is normally reabsorbed back into the blood by the kidneys. Its presence in urine may indicate a health problem such as diabetes.
Which excretory organ is found in earthworms?
- A Flame cells
- B Malpighian tubules
- C Nephridia
- D Kidneys
Correct answer: Nephridia
Earthworms have nephridia as their excretory organs. These structures help remove nitrogenous wastes and maintain water balance.
Which excretory structures are found in insects such as cockroaches?
- A Paired nephridia
- B Paired kidneys
- C External gills only
- D Malpighian tubules
Correct answer: Malpighian tubules
Malpighian tubules are the excretory organs of many insects. They help remove nitrogenous wastes and conserve water.
Which excretory structure is found in flatworms such as Planaria?
- A Kidneys
- B Malpighian tubules
- C Flame cells
- D Lungs
Correct answer: Flame cells
Flatworms such as Planaria use flame cells for excretion and osmoregulation. These cells help remove excess water and wastes from the body.
What is osmoregulation?
- A Control of body temperature only
- B Breaking down food in the stomach
- C Formation of new red blood cells
- D Regulation of water and salt balance
Correct answer: Regulation of water and salt balance
Osmoregulation is the process of maintaining the proper balance of water and salts in the body. It is closely linked with excretion, especially in animals living in different environments.
Dialysis is used when which organ fails to work properly?
- A Lung
- B Stomach
- C Kidney
- D Eye
Correct answer: Kidney
Dialysis is an artificial method of filtering blood when the kidneys cannot function properly. It removes wastes and excess water from the blood.