Explain4 marksStandard
Explain how the uptake of potassium ions into guard cells leads to the opening of a stoma.
CAIE A Level Biology 9700 · Homeostasis
Homeostasis: explain question
How this question is marked
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
More Homeostasis questions
- 4 marks · A small number of glucagon molecules can cause the rapid breakdown of a large amount of glycogen in liver cells. Explain how this…
- 4 marks · The table below shows the blood glucose concentration of a healthy mammal at intervals after a meal. Time after meal (min) Blood glucose…
- 5 marks · A tomato plant in a garden is observed on a hot, dry afternoon. The leaves appear wilted, but by the evening they have fully recovered. A…
- 4 marks · In response to low blood glucose, the pancreas releases a small amount of glucagon into the blood. Outline how this small signal is…
- 4 marks · The table below shows the mean stomatal aperture (width in micrometres) measured every 2 hours over a 24-hour period in leaves of a…
- 5 marks · Explain the sequence of events that occur in the body when the water potential of the blood decreases, leading to increased water…
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.