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