IMO Practice Test — Life Processes
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
A potted plant is kept in the dark for 48 hours and then a leaf is tested with iodine. It does not turn blue-black because:
No starch was made without light (photosynthesis stopped)
Starch was made faster
Iodine does not work in the dark
The leaf turned green
Explanation: Without light, photosynthesis stops, so no starch forms and iodine gives no blue-black colour.
Question 2 of 6
Why is the wall of the left ventricle thicker than that of the right ventricle?
It pumps blood to the whole body, against greater resistance
It pumps blood only to the lungs
It stores more food
It filters blood
Explanation: The left ventricle pumps oxygenated blood to the entire body, needing more force, so its wall is thicker.
Question 3 of 6
An athlete breathes faster and deeper during a race mainly to:
Supply more oxygen for aerobic respiration in muscles
Remove starch
Cool the lungs
Make more urea
Explanation: Hard exercise needs more oxygen for aerobic respiration to release energy, so breathing rate increases.
Question 4 of 6
Reabsorption of glucose and most water in the nephron ensures that:
Useful substances are not lost in urine
More urea is made
Blood pressure falls to zero
Digestion is completed
Explanation: Selective reabsorption returns useful glucose, salts and water to the blood, so only waste is excreted.
Question 5 of 6
Transpiration is useful to a plant because, besides cooling it, it mainly helps to:
Pull water and minerals up through the xylem
Make food
Store starch
Digest proteins
Explanation: The loss of water vapour creates a pull (transpiration pull) that draws water and minerals up the xylem.
Question 6 of 6
A person whose kidneys have failed is put on dialysis. Dialysis works by:
Filtering wastes like urea out of the blood artificially
Adding urea to the blood
Digesting food
Making the heart beat
Explanation: Dialysis artificially filters nitrogenous wastes from the blood, doing the kidney's job.