The number of moles of oxygen produced/consumed in the experiment..?
Laboratory experiments such as this allow researchers to measure
photosynthesis and respiration in organisms under highly controlled
conditions. For example, in this experiment the temperature was maintained
at 18 °C.
Suggest why the temperature was kept constant and what effects there may
have been on a test sample if the temperature had increased or decreased by a
few degrees during the experiment. (100–150 words)
(d) The number of moles of oxygen produced/consumed in the experiment
described in Table 1 can be related to the amount of energy stored or released
by the phytoplankton. If you assume that one mole of oxygen is equivalent to
500 kJ (3 sig figs) of energy, convert the values in Table 1 into units of
energy stored/released per hour, and display your answer as a new table.
(Hint: the energy for the first species Amphidinium carterae has been
calculated for you in Table 2 below. Calculate the energy for the other two
species, showing your working, then construct a new table to display the
results for all three species.)Table 2 Energy stored/released per hour.
Species of Conditions Rate of change in oxygen Energy/kJ h−1
phytoplankton light concentration/μmol O2 h−1 0.0131
Amphidinium carterae dark 26.2
−7.50 −0.00375
(e) Using the experimental data shown in Table 1 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.)
(f) In recent years phytoplankton have been investigated as a potential source of
energy for humans. Researchers have therefore been interested in whether
these organisms could be 'farmed' to provide food or fuel. In terms of
biomass, Gross Primary Production (GPP) in phytoplankton living in a layer
just below the surface of a typical ocean area is 4102 g m−2 yr−1 If you .
assume the energy value of phytoplankton is 6 kJ g−1 ,calculate the GPP in
terms of kJ m−2 yr−1 .Show your working clearly .
(g) If a human needs to eat about 10 000 kJ per day, estimate (to the nearest
gram) the mass of phytoplankton that would be required to meet their daily
energy requirements. Based on this value, approximately what proportion of
her own body weight in phytoplankton would a 60 kg woman need to eat
over the course of a year, if this were her only source of energy? Show your
working clearly.
(h) Farming phytoplankton to harness solar energy for human food or fuel would
presumably require cultivating large numbers of these organisms in a
carefully designed artificial environment. Suggest two features that could be
incorporated into the design of a phytoplankton 'farm' to optimise the Net
Primary Production (NPP). Briefly describe why each design feature would
be useful. (One sentence for each)