Active Transport (Cambridge O Level Biology)

The scientists bubbled oxygen through the solution of one group and pure nitrogen gas through the solution of the other group. Nitrogen gas will remove all dissolved oxygen from the solution. 

The level of radioactive magnesium ions was measured at the start of the experiment and again, every 30 minutes for five hours. The scientists subtracted the level of magnesium ions in the solution from the starting level as a way of determining the uptake of magnesium ions by the plant. Table 1 shows the scientists' results.

Table 1

Plot a line graph of the results shown in Table 1.

[4]

State the solution the carrot seedlings absorbed more magnesium ions from.

[1]

Identify the independent and dependent variables in the investigation.

[2]

Identify a variable that needs to be kept constant (control variable) throughout the investigation. 

[1]

Calculate the percentage increase of magnesium ions absorbed with oxygen between 120 minutes and 300 minutes. 

[3]

Calculate the range for the level of magnesium ions absorbed without oxygen from the beginning to the end of the experiment.

[1]

Describe how the scientists could make the results reliable.

Explain why the scientists took data over a five hour period.