Photosynthesis and respiration comparedIB MYP Biology: Subtopic test

1. 1
   A sealed glass bottle garden in a flat in Singapore contains soil, several small green plants and a few snails. It has been kept in a bright room for two years without ever being opened, and everything in it is still alive.

   (a)

   In which part of a plant cell does photosynthesis take place?

   [1 mark]

   • AThe mitochondria
   • BThe nucleus
   • CThe vacuole
   • DThe chloroplasts

   (b)

   Which statement correctly compares photosynthesis with respiration?

   [1 mark]

   • ABoth processes release energy
   • BPhotosynthesis takes in energy from light, whereas respiration releases energy
   • CPhotosynthesis happens only in animals and respiration only in plants
   • DPhotosynthesis makes carbon dioxide and respiration uses it

   (c)

   Explain how the gases in the sealed bottle stay balanced so that the plants and snails stay alive.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Large areas of tropical rainforest are being cleared for farmland, and the trees are often burned. Scientists are measuring the effect on the gases in the atmosphere. Every living organism uses oxygen in respiration, yet the oxygen level in the atmosphere has stayed at about 21% for a very long time.

   (a)

   What is the effect of clearing and burning large areas of forest on the carbon dioxide level in the atmosphere?

   [1 mark]

   • AIt falls, because trees release carbon dioxide
   • BIt stays the same, because animals take the place of the trees
   • CIt rises, because less carbon dioxide is taken in by photosynthesis
   • DIt falls, because respiration stops

   (b)

   Which process removes carbon dioxide from the atmosphere and releases oxygen?

   [1 mark]

   • APhotosynthesis
   • BRespiration
   • CBurning
   • DFermentation

   (c)

   Explain why the oxygen level in the atmosphere stays roughly constant even though all living organisms use oxygen.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates respiration in bean seeds using hydrogencarbonate indicator, which is red in normal air, turns yellow when the carbon dioxide level rises and turns purple when it falls. She puts 10 germinating bean seeds on a gauze platform above 10 cm³ of indicator in tube 1, and 10 boiled bean seeds on a gauze platform above 10 cm³ of indicator in tube 2. She seals both tubes with bungs and keeps them in a dark cupboard at 20 °C for four hours. Afterwards the indicator in tube 1 is yellow and the indicator in tube 2 is still red.

   (a)

   Explain the colour change of the indicator in tube 1.

   [3 marks]

   (b)

   Evaluate the investigation: state the purpose of tube 2 and suggest two improvements.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A government agency on the coast of Abu Dhabi has planted thousands of mangrove trees to help to reduce the carbon dioxide level in the atmosphere. Mangroves grow in shallow salty water, and their roots shelter young fish.

   (a)

   Compare photosynthesis and respiration in plant cells in terms of reactants, products, location and energy change.

   [6 marks]

   (b)

   Discuss and evaluate whether planting mangrove forests is a good way to reduce the carbon dioxide level in the atmosphere.

   [6 marks]

   Total for question 4: 12 marks

End of questions