Excretion in Humans is one of 10 topics in the Grade 11 Life Sciences CAPS syllabus, covered across 3 lessons on Study Vault. Below are real practice questions from this topic with full worked answers.
Sample practice questions
Easy
1. Excretion is best defined as:
The removal of metabolic waste products produced by the body's own chemical reactions
The elimination of undigested food waste from the digestive tract
The absorption of nutrients into the bloodstream
The intake of food into the body
Answer: The removal of metabolic waste products produced by the body's own chemical reactions — Excretion is the removal of metabolic waste products (such as carbon dioxide and urea) produced by the body's own chemical reactions, distinct from egestion, which removes undigested food waste that never entered the body's cells.
Easy
2. Which organ is the main excretory organ, filtering the blood to remove urea, excess water, and excess salts?
The kidneys
The lungs
The skin
The bladder
Answer: The kidneys — The kidneys are the main excretory organs of the human body, filtering the blood extensively to remove urea, excess water, and excess salts, producing urine.
Medium
3. What process does the liver use to convert excess amino acids into the less toxic waste product urea?
Deamination, converting toxic ammonia into urea
Filtration, as occurs in the kidney nephrons
Fermentation, as occurs during anaerobic respiration
Egestion, removing amino acids directly from the gut
Answer: Deamination, converting toxic ammonia into urea — The liver breaks down excess amino acids through deamination, converting the toxic ammonia produced into the much less toxic urea, which is then transported in the blood to the kidneys for excretion.
