AS 2 2023-style sampling and practical question · 5 marks
Describe how you would use a quadrat and a transect to investigate the distribution of a plant species across a sand dune.
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CCEA AS Biology 2023 past paper and mark scheme
Summer 2023 is part of the current CCEA GCE Biology (2016) specification, so every question style in it is still examinable. The papers and mark schemes themselves are published by CCEA; BioCCEA is an independent study tool and is not endorsed by CCEA.
What you sit in AS 2023
AS 1: Molecules and Cells
AS 1 written paper (1 hour 30 minutes)
Biological molecules, enzymes, cell structure, transport across membranes, cell division, nucleic acids and the immune response.
AS 1 topic list and exam focusAS 2: Organisms and Biodiversity
AS 2 written paper (1 hour 30 minutes)
Gaseous exchange, transport in plants and mammals, adaptation, biodiversity, classification, sampling and human impact.
AS 2 topic list and exam focusAS 3: Practical Skills in AS Biology
AS 3 practical booklet plus a written practical-skills paper (1 hour)
Planning, manipulating apparatus, recording, processing and evaluating experimental data at AS level.
AS 3 topic list and exam focus
How to sit the 2023 paper properly
- 1Print the paper and sit it in one block, to time, with no notes. A paper done in pieces tells you nothing about your exam performance.
- 2Mark it with the official CCEA mark scheme in front of you and award a mark only where the scheme's point is actually made.
- 3Log every dropped mark by unit topic, not by question number, so patterns appear across papers.
- 4Rewrite the two worst answers in full, using mark-scheme wording, then re-mark them.
- 5Come back to the same paper three weeks later and redo only the questions you lost marks on.
Sit the AS 2023 style questions
Answer each one under exam conditions. Your wording is marked against every mark scheme point before the full-mark answer appears.
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These questions are written in the style of the CCEA GCE Biology (2016) papers and are not reproduced from any live paper. CCEA owns the copyright in its question papers and mark schemes — always download the official paper and mark scheme from CCEA and use these worked answers alongside them. BioCCEA is an independent study tool and is not endorsed by CCEA.
Worked AS 2023 questions with mark schemes
Question styles that carried the most marks in the Summer 2023 papers, each with the full list of creditworthy mark scheme points, a model answer at full marks, and the marking point candidates most often missed.
AS 2 2023-style sampling and practical question · 5 marks
Describe how you would use a quadrat and a transect to investigate the distribution of a plant species across a sand dune.
Command word: Describe — how to answer itMark scheme — 5 creditworthy points
- Lay a tape (belt or line transect) from the strandline inland, along the environmental gradient
- Place quadrats at regular intervals along the transect (systematic sampling), stating the interval
- Record percentage cover or frequency of the species in each quadrat
- Repeat with several parallel transects to increase reliability and calculate a mean
- Measure an abiotic factor at each point (e.g. soil moisture, pH) so distribution can be related to it
Full-mark answer
I would lay a tape measure as a belt transect from the strandline inland, along the environmental gradient of the dune. Quadrats would be placed at regular intervals, for example every 5 metres, because this is systematic sampling along a gradient rather than random sampling. In each quadrat I would record the percentage cover, or the frequency, of the plant species. I would repeat the procedure along several parallel transects and calculate a mean for each distance to improve reliability. At each quadrat position I would also measure abiotic factors such as soil moisture content and pH, so the distribution of the species can be related to the changing conditions along the dune.
Examiner insight: Examiners specifically look for the justification that sampling is systematic, not random, because there is a gradient. That single sentence is often the difference between 3 and 5.
AS 2 2023-style heart structure question · 6 marks
Explain how the structure of the mammalian heart ensures that oxygenated and deoxygenated blood are kept separate and that blood flows in one direction only.
Command word: Explain — how to answer itMark scheme — 6 creditworthy points
- The septum separates the right side (deoxygenated) from the left side (oxygenated)
- Deoxygenated blood enters the right atrium from the vena cava and leaves via the pulmonary artery to the lungs
- Oxygenated blood returns to the left atrium in the pulmonary vein and leaves via the aorta
- Atrioventricular valves close when ventricular pressure exceeds atrial pressure, preventing backflow into the atria
- Semi-lunar valves close when arterial pressure exceeds ventricular pressure, preventing backflow from the arteries
- The left ventricle wall is thicker to generate the higher pressure needed for the systemic circulation
Full-mark answer
A muscular septum divides the heart so that the deoxygenated blood on the right side never mixes with the oxygenated blood on the left. Deoxygenated blood from the body enters the right atrium through the vena cava, passes into the right ventricle and is pumped through the pulmonary artery to the lungs, while oxygenated blood returns in the pulmonary vein to the left atrium, passes into the left ventricle and is pumped out through the aorta. One-way flow is ensured by valves: the atrioventricular valves close as soon as ventricular pressure rises above atrial pressure, preventing backflow into the atria, and the semi-lunar valves close when the pressure in the arteries exceeds that in the emptying ventricles, preventing backflow from the arteries. The wall of the left ventricle is much thicker than that of the right because it must generate a far higher pressure to force blood around the whole body.
Examiner insight: Valve marks require the pressure relationship, not just 'valves stop backflow'. Naming the vessel that each chamber connects to is where careless answers lose marks.
AS 1 2023-style food test practical question · 6 marks
Describe how you would test a solution for the presence of reducing sugar, non-reducing sugar, starch and protein.
Command word: Describe — how to answer itMark scheme — 6 creditworthy points
- Reducing sugar: add Benedict's solution and heat in a water bath; brick-red precipitate is positive
- Non-reducing sugar: after a negative Benedict's test, boil with dilute hydrochloric acid to hydrolyse, neutralise with sodium hydrogencarbonate, then repeat Benedict's
- Starch: add iodine in potassium iodide solution; blue-black colour is positive
- Protein: add Biuret reagent (or sodium hydroxide then copper sulfate); purple/lilac colour is positive
- A negative result must be stated for comparison (Benedict's stays blue, iodine stays orange-brown)
- Semi-quantitative point: the intensity of the colour or a colorimeter reading indicates concentration
Full-mark answer
To test for a reducing sugar I would add an excess of Benedict's solution and heat the mixture in a water bath at about 80 degrees Celsius; a brick-red precipitate is a positive result, while the solution staying blue is negative. If that test is negative I would test for a non-reducing sugar by boiling a fresh sample with dilute hydrochloric acid to hydrolyse it, neutralising with sodium hydrogencarbonate, and then repeating the Benedict's test - a brick-red precipitate now shows a non-reducing sugar was present. For starch I would add a few drops of iodine in potassium iodide solution to the sample at room temperature; a blue-black colour is positive and orange-brown is negative. For protein I would add Biuret reagent, and a purple or lilac colour indicates protein. The intensity of the Benedict's colour, or a colorimeter reading, can be used to compare concentrations semi-quantitatively.
Examiner insight: The non-reducing sugar sequence must include neutralisation - omitting it is the single most common error. Always give the negative result as well as the positive.
These questions are written in the style of the CCEA GCE Biology (2016) papers and are not reproduced from any live paper. CCEA owns the copyright in its question papers and mark schemes — always download the official paper and mark scheme from CCEA and use these worked answers alongside them. BioCCEA is an independent study tool and is not endorsed by CCEA.
Download the official CCEA paper and mark schemePractise the AS 2023 paper in the app
These open BioCCEA with AS already selected, so you can sit questions in this paper's style and have them marked against the CCEA mark scheme.
Get your 2023 answers marked
Photograph a written answer from this paper and see it marked line by line in CCEA mark-scheme language, with the exact phrase you needed to earn each missing mark.