Excretion and the kidneyIB MYP Biology: Subtopic test

1. 1
   A runner completes a marathon in Nairobi on a hot day. Afterwards she is breathing deeply, her skin is wet with sweat, and she passes only a small volume of dark yellow urine.

   (a)

   Which row correctly pairs an organ with a waste substance that it excretes?

   [1 mark]

   • ALungs – urea
   • BKidneys – urea
   • CSkin – carbon dioxide
   • DSkin – glucose

   (b)

   Urea is made from the breakdown of excess amino acids. Where in the body is urea made?

   [1 mark]

   • AKidneys
   • BBladder
   • CSkin
   • DLiver

   (c)

   Explain why the runner passes only a small volume of dark yellow urine.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A patient in Lagos has a kidney infection. A urine test finds protein in her urine, which is not normally present in healthy urine. Her doctor says that her kidneys are not working as well as they should.

   (a)

   Which statement describes the function of healthy kidneys?

   [1 mark]

   • AThey make urea from excess amino acids
   • BThey absorb digested food into the blood
   • CThey filter the blood, removing urea and extra water and salts to form urine
   • DThey exchange oxygen and carbon dioxide with the blood

   (b)

   Which substance is normally present in healthy urine?

   [1 mark]

   • AUrea
   • BProtein
   • CRed blood cells
   • DGlucose

   (c)

   Explain why protein is not normally found in urine, and why it appears in urine when the kidneys are damaged.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A sports scientist investigates whether exercising in hot conditions changes how much urine a person produces. Four volunteers each do two hours of gentle exercise in a room at 20 °C, and on another day in a room at 35 °C. Each volunteer drinks 500 mL of water at the start. The mean volume of urine collected over the two hours is 310 mL at 20 °C and 140 mL at 35 °C.

   (a)

   State the trend in the results and calculate the percentage decrease in mean urine volume at 35 °C compared with 20 °C. Give your answer to the nearest whole number.

   [3 marks]

   (b)

   Explain the results using ideas about water balance, and evaluate one weakness of the investigation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In several countries in the Gulf, outdoor work is banned during the hottest hours of summer days, and employers must provide shade and drinking water. Construction workers can lose several litres of water as sweat during a long shift in the heat.

   (a)

   Explain how a construction worker's body loses water and waste products on a hot day, and how the kidneys help to keep the body's water balance.

   [6 marks]

   (b)

   Discuss and evaluate the rules that ban outdoor work in the hottest hours and require employers to provide shade and drinking water.

   [6 marks]

   Total for question 4: 12 marks

End of questions