Practise Edexcel IGCSE Biology data analysis, communication and evaluation by interpreting graphs, discussing conclusions and judging validity.
Micropropagation is used to produce plant clones.
The process involves growing explants in vitro.
The explants grow new roots and shoots.
A student investigates the effect of pH on the growth of new shoots.
The table shows the student's results.
Explain the relationship between pH and the mean number of shoots per explant.
The diagram shows a section through the human eye.
When a person looks directly at an object, light is focused on the fovea of the retina.
Scientists are developing a new treatment for AMD. The treatment involves an operation to replace the damaged cells in the fovea with new cells.
Early results show an improvement in the condition. However, the treatment has only been tested on two patients.
Suggest what else scientists need to do before the treatment is allowed to be used for all patients with AMD.
Apples contain an enzyme called phenol oxidase.
When apple tissue is exposed to oxygen in the air, this enzyme turns the apple tissue brown.
A student uses this method to investigate the effect of pH on the time taken for apple tissue to turn brown.
- mash an apple to produce a pulp
- place 25 g of this pulp into a beaker
- mix a pH 7 buffer with the pulp to maintain the pH
- check the colour of the pulp every five minutes
- record the time when the pulp turns brown
The student repeats this method using pH buffers of 3, 5, 9, and 11.
The graph shows the student's results.
Explain how the student could modify this method to give a more accurate measure of the time taken for the apple pulp to turn brown.