Questions with 1, 2, 3 or 4 marks usually start with command words. If a question starts with the command word 'state', 'give', 'name' or 'write down', it needs a short answer only. This type of question can often be answered with one word or phrase.
It is important to state, give, name or write down the number of things that the question asks for. If you write down fewer, you cannot get all the marks. If you write down more, and one is wrong, you might lose a mark.
Some questions start with the command words 'describe', 'explain' or 'compare'. These are often worth two or more marks:
More complex structured questions will be worth three or four marks. They include questions with complex descriptions and explanations, and questions in which you need to compare things.
Some of the answers are shown here as bullet points. This is to show clearly how a mark can be obtained. However, do not use bullet points in your answers - the points must be linked together logically.
This page contains AQA material which is reproduced by permission of AQA.
An athlete ran as fast as he could until he was exhausted.
The graphs below show the concentrations of glucose and of lactic acid in the athlete's blood at the start and at the end of the run.
a) Lactic acid is made during anaerobic respiration.
What does anaerobic mean? [1 mark]
b) Give evidence from the graphs that the athlete respired anaerobically during the run. [1 mark]
a) Without oxygen .
b) More / high / increased lactic acid (at end) .
Photosynthesis uses carbon dioxide to make glucose.
Complete the equation for photosynthesis. [2 marks]
Carbon dioxide + ______ → glucose + ______
Carbon dioxide + water → glucose + oxygen 
Below is a cross section through a plant root.
a) What is tissue A? [1 mark]
b) A student is given samples of two fluids.
One fluid is from the phloem of a plant and one from the xylem of a plant.
The student is asked to work out which fluid is from the phloem and which is from the xylem.
She measures the pH and the concentrations of sugar, nitrate ions and potassium ions of each fluid.
The table shows the student’s results.
|Fluid A||Fluid B|
|Sugar in mg/cm3||118||1.18|
|Nitrate ions in mg/cm3||10||600|
|Potassium ions in μg/cm3||1.18||2,500|
Which fluid is from the phloem and which is from the xylem?
Explain your answer.
Use information from the table above. [4 marks]
a) Xylem .
b) Fluid A is phloem. Fluid B is xylem .
Any three from:
a) Carbon dioxide enters a plant through the stomata on the leaves.
Name the cells that control the size of the stomata. [1 mark]
b) Scientists grew tomato plants in air containing different concentrations of carbon dioxide.
The scientists recorded the number of stomata found on the lower surface of the leaves of plants grown at each carbon dioxide concentration.
Here is a graph showing the results of the investigation.
i) Describe the relationship between the mean number of stomata per mm2 and the mean carbon dioxide concentration. [2 marks]
ii) Suggest a reason for the relationship you described in bi). [1 mark]
i) Suggest one disadvantage of a plant having a large number of stomata per mm2 on each leaf. [1 mark]
ii) Suggest one environmental condition where a large number of stomata per mm2 on each leaf would be a disadvantage. [1 mark]
a) Guard cells .
i) As carbon dioxide concentration increases, the mean number of stomata decreases  and there is a rapid drop initially .
ii) More carbon dioxide so plant doesn't need as many stomata (to obtain the amount needed) or less carbon dioxide so the plant needs more stomata (to obtain enough) .
i) It may lose too much water .
ii) Any one answer from: