Species of phytoplankton Conditions Rate of change in oxygen concentration/µmol
ID: 9797 • Letter: S
Question
Species of phytoplankton Conditions Rate of change in oxygenconcentration/µmol O2 h-1
Amphidinium carterae light 26.2
dark _ 7.50
Biddulphia aurita light 40.3
dark _5.10
Chaetoceros didymum light 26.1
dark _6.30
Using the experimental data shown above for Amphidinium carterae
calculate what percentage of the total energy assimilated in light conditions
in 1 hour is used for respiration in this organism. Show your working clearly
and give your answer to the appropriate number of significant figures. (Hint:
you will need to use the data from the dark condition as well as the light
condition in your calculation.)
It is clear that there are some differences between the species in above, but
all three species show the same overall pattern of increase/decrease in oxygen
concentration with time in the light/dark, respectively. Use your
understanding of photosynthesis and respiration to explain why under some
conditions in the experiment the oxygen concentration increased (a positive
number in above) and under other conditions the oxygen concentration
decreased (a negative number in above). (100–150 words)
Explanation / Answer
Energy stored and released in KJ per hour is calculated from the rate of change in oxygen concentration.
Convert the um into mol and multiply with the energy released from the one mole of oxygen molecule.
one mole of oxygen is equivalent = 500 kJ of energy
phytoplankton Rate of change in oxygen Energy/ kJ h1
and conditions
concentration/mol O2h1
Amphidinium
carterae
Light 26.2 = 26.2 x 500 kJ x 10-6 = 0.0131 kJ / h
Dark -7.50 = -7.50 x 500 kJ x 10-6 = -0.00375 kJ / h
Biddulphia aurita
light 40.3 = 40.3 x 500 kJ x 10-6 = 0.0201 kJ / h
Chaetoceros didymum
light 26.1 = 26.1 x 500 kJ x 10-6 = 0.0130 kJ /h
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