Practise Paper 3 by planning fair tests, making accurate biological observations and measurements, presenting results, and drawing evidence-based conclusions.
The table shows the volume of water taken up over a 10 minute period for two species of plant, X and Y .
Both plants were tested at the same time, in the same room and using identical potometers. A student concluded that Y was a xerophyte so lost less water.
What feature of the experiment could bring this conclusion into doubt?
The student did not control air flow or temperature surrounding the plants.
The student did not leave the plants to acclimatise to their surroundings.
The student did not take measurements at 0 minutes.
The student did not take account of the area of leaves.
Alveolar macrophages are cells of the immune system that remain in the alveolar region of the gas exchange system. The macrophages protect against infection caused by pathogens that have been inhaled.
Alveolar macrophages have the same cell structures as typical animal cells.
Fig. 2.1 is a diagram of an alveolar macrophage showing:
- some of the cell structures that would be visible using an electron microscope
- a newly formed phagocytic vacuole (phagosome) containing two cells of Mycobacterium tuberculosis.
Fig. 2.1
The cell structures with the functions described in Table 2.1 are not shown in Fig. 2.1.
Complete Fig. 2.1 by drawing and labelling the cell structures described in Table 2.1.
When making measurements in experiments, which methods could have parallax errors?
1 using a calibrated eyepiece graticule to measure length
2 using a measuring cylinder to measure volume
3 using a ruler to measure length of a shoot
1, 2 and 3
1 and 2 only
1 and 3 only
2 and 3 only
The graph shows the percentage of tuberculosis (TB) patients who were also known to be infected with HIV, from 2004 to 2011.
Which statement about the graph is correct?
From 2004 to 2010, the percentage of TB patients with HIV infection in region P increased from 3% to 69%.
From 2005 to 2011, the percentage of TB patients with HIV infection increased more rapidly in region P than in regions outside region P.
From 2006 to 2011, the percentage of TB patients with HIV infection in regions outside region P doubled.
From 2007 to 2011, the percentage of TB patients with HIV infection globally increased from 20% to 30%.
A student carried out the Benedict's test on four different concentrations of glucose solution and then recorded the time taken for the first appearance of a colour change (the end-point).
The student found it difficult to identify the first appearance of a colour change and consistently timed each solution for two seconds after the colour change first appeared. This introduced a source of error into the experiment.
Which statements about this error are correct?
1 The effect of the error will be reduced if the student performs three repeats at each concentration of glucose.
2 The error will prevent the student from identifying which solution has the highest concentration of glucose.
3 The error is systematic as the student consistently timed each solution for two seconds after the end-point.
1 and 2
1 and 3
2 and 3
3 only