A respirometer can be used to investigate how temperature affects the rate of respiration of woodlice. Woodlice are small invertebrate animals. Fig. 2.1 shows a single woodlouse. [Figure 2.1] Fig. 2.2 shows a simple respirometer. [Figure 2.2]

Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

1. [4] (a) any four from: 1 sodium hydroxide absorbs, carbon dioxide / CO2, released by, woodlice / respiration ; 2 oxygen / O2, taken in reduces pressure (in boiling tube); 3 drop of liquid moves towards, boiling tube / bung / woodlice / left; 4 measure, distance / length, moved by drop, in set time; 5 rate = distance divided by time; 6 detail of calculation of volume of O2 used;
2. [1] (b) rate at 5 °C: lower/slower and less/lower, kinetic energy or fewer enzyme-substrate, collisions / complexes or fewer, enzyme-catalysed / respiration / glycolysis / link reaction / Krebs cycle, reactions ;