Develop experimental skills by selecting control variables, explaining how fixed apparatus keeps conditions constant and identifying anomalies in biological data.
Some students set up the apparatus shown in Fig. 6.1 to compare transpiration in two sets of leaves.
Set A was kept in a transparent bag and set B was left in the open air.
All other conditions were kept constant.
The mass of the leaves in each set was measured at the start of the investigation and after five hours.
Fig. 6.1
The students needed two additional pieces of apparatus to take measurements so that they could calculate the rate of transpiration from their results.
State the two additional pieces of apparatus the students needed to take the measurements.
1
2
State why the student:
kept the lamp at the same distance during the investigation,
Acid rain has negative effects on many ecosystems.
Two groups of students were asked to investigate the effects of acid rain on the germination of pine tree seeds.
Both groups of students decided to use sulfuric acid rather than hydrochloric acid to represent acid rain in their investigation.
Suggest why.
The second group of students placed 100 seeds in each of five Petri dishes, labelled 1 to 5. Group 2 used the same range of pH values as group 1.
They recorded the percentage of seeds that had germinated after 72 hours.
Their results are shown in Table 5.2.
Table 5.2
The teacher thought that group 2 had forgotten to add the sulfuric acid to one of their Petri dishes.
Suggest which Petri dish was not set up correctly.