IB ESS HL 2.2.24 Hl Secondary Productivity Questions

Calculate and interpret secondary productivity from consumer energy budgets.

Exam points

distinguish GSP and NSP as consumer biomass after faecal and respiratory losses
calculate GSP from food eaten minus faecal loss and select data with area and time units
design an NSP estimate using mark-release-recapture, dry biomass change and respiratory data

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Study 2.2.24 (HL)—Secondary productivity conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 7]

Suggest a series of procedures that could be used to estimate the net productivity of an insect population in $\mathrm{kg} \mathrm{m}^{-2} \mathrm{yr}^{-1}$ .

measure change in population size over year;
using Lincoln Index/mark-release-recapture;
set traps/capture a sample, mark and release them;
re-set traps for a second capture and calculate the proportion marked and unmarked;
use the equation: $N=\frac{n_{1} \times n_{2}}{n_{3}}$ ;
weigh a sample of insects to find (wet) weight;
use a conversion factor to calculate dry weight from (wet) weight;
calculate mean dry weight/biomass per individual;
from mean dry weights and population sizes calculate total weight change over year;
estimate area occupied by population using measuring tapes/scale maps;
divide total change in dry mass by area in $\mathrm{m}^{2}$ ;

Marking guidance:

Award [1] for each correct suggestion, up to [7 max].
Credit any alternative sequence of procedures that is equally appropriate to finding net secondary productivity eg using lab population and weighing dry weight of food, faeces, respiration rates, etc, awarding marks similarly to scheme above.

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IB ESS HL 2.2.24 Hl Secondary Productivity Questions question 1