Skip to content
MathsGenie logo
Open app

Course home

  1. IGCSE
  3. Biology Edexcel
  5. Question bank

Nutrition

EasyMediumHard
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253
Question 7

A student investigates how light affects photosynthesis in the aquatic plant Elodea (pondweed) by monitoring changes in carbon dioxide levels.

The student uses the following method:

  • Step 1: Place 5 cm35\text{ cm}^35 cm3 of red-orange hydrogen-carbonate indicator solution into each of three test tubes, X, Y, and Z.
  • Step 2: Place a 5 cm5\text{ cm}5 cm sprig of Elodea into tube X and another 5 cm5\text{ cm}5 cm sprig of Elodea into tube Y.
  • Step 3: Wrap tube Y completely in black card to exclude light.
  • Step 4: Seal all three tubes with airtight bungs to prevent gas exchange with the atmosphere.
  • Step 5: Place the tubes 20 cm20\text{ cm}20 cm away from a bright lamp in a room with a temperature controlled at 21∘C21^\circ\text{C}21∘C for three hours.
a.

(i) Explain the purpose of tube Z in this investigation. (ii) Why is it necessary to keep the temperature of the room constant? (iii) Name the independent variable in this investigation.

[5]
b.

The table shows the student's results:

Test tubePlant presentLight conditionsColour of indicator at startColour of indicator after three hours
XYesLightRed-orangePurple
YYesDarkRed-orangeYellow
ZNoLightRed-orangeRed-orange

(i) Explain the change in colour of the indicator in tube X. (ii) Explain the change in colour of the indicator in tube Y.

[6]
c.

Suggest a different method that the student could use to show that light intensity affects the rate of photosynthesis in Elodea.

[4]

Nutrition Questions

  1. IGCSE
  2. /Biology
  3. /Nutrition