CCEA AS Biology: how the 200 marks split across AS 1, AS 2 and the Practical Skills paper, the water potential and graph-drawing conventions examiners keep marking down, and legal on-the-fly calculator techniques for rate and diversity index questions.
阅读时间 3 分钟更新于: 2026年9月3日
试卷概览
卷数
3
总分
200
考试时间
4小时
题型
12
试卷
时间
分数
题数
比重
题型
AS 1
1小时 30分钟
75
8
38%
Short answer / terminology recall, Structured mechanism and energy profiles, Experimental data analysis and cell physiology, Extended response essay
AS 2
1小时 30分钟
75
8
37%
Short structured and classification recall, Physiological and ecological data analysis, Numerical calculations, Extended response essay
AS 3, practical skills
1小时
50
7
25%
Biochemical food tests and micrograph identification, Microscope graticule calibration and measurement, Fieldwork methodology and respirometer rate calculations, Graph plotting and data interpretation
评级
ABCDEU
计算器规定
Scientific calculators are permitted and needed throughout, particularly in AS 3 for rate, magnification and diversity index calculations. The standard JCQ rule applies: no computer algebra or symbolic manipulation function, no communication with another device, and no retrievable information of any kind, including formulae, notes or programs, stored in the calculator. Clear the calculator's memory before the exam or activate its exam mode; a manual reset alone does not clear stored data.
AO1: Demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures. (37%)
AO2: Apply knowledge and understanding of scientific ideas, processes, techniques and procedures in a theoretical context, in a practical context, when handling qualitative data, and when handling quantitative data. (38%)
AO3: Analyse, interpret and evaluate scientific information, ideas and evidence to make judgements and reach conclusions, and to develop and refine practical design and procedures. (25%)
Chaining a respirometer or fieldwork rate calculation
Casio fx-83/85 series (scientific)
用途: Get an accurate rate with the correct unit without compounding rounding errors.
使用时机: Any AS 3 practical question asking for a rate, such as oxygen uptake or a fieldwork measurement, from a volume or count and a time.
步骤
Work out the rate as one continuous calculator entry, volume or count divided by time, keeping every measurement in the same units before you divide, and do the division last so intermediate values are not rounded and re-entered.
考试提示: This is an on-the-fly calculation done live during the exam using the calculator's ordinary arithmetic keys. CCEA and JCQ rules do not permit any formula, note or program to be stored in the calculator beforehand. Activate exam mode if your calculator has one.
Magnification from a graticule in one pass
Casio fx-83/85 series (scientific)
用途: Avoid the factor-of-a-thousand error that comes from dividing before converting units.
使用时机: Microscopy questions that ask for a real size from an eyepiece graticule reading and a magnification.
步骤
Convert the measured length to micrometres first, multiplying by 1000 if starting in millimetres, then divide by the magnification value in the same working line, so the conversion step cannot be accidentally skipped.
考试提示: Perform this conversion using the calculator's standard functions during the exam. No conversion table, formula or note may be stored in the calculator; everything must be entered fresh from the question.
Memory key for a diversity index
Casio fx-83/85 series (scientific)
用途: Total the per-species contributions to an index accurately without adding a long list of numbers by hand.
使用时机: Biodiversity questions that ask for an index built from a sum across several species, such as n multiplied by n minus 1 for each species.
步骤
Calculate each species' contribution to the sum and add it to the calculator's memory with M+ as you go, then use memory recall for the running total instead of adding the list by hand at the end.
考试提示: M+ and memory recall are standard, permitted arithmetic functions used live during the exam with data taken from the question. They must not be used to retrieve any information stored before the exam started.
常见错误
1medium涉及分数: 1Exchange surfaces
Villi and microvilli are used interchangeably, when villi are multicellular folds of intestinal tissue and microvilli are sub-cellular folds of an individual cell's membrane.
如何避免: Fix the scale in your head before writing: villi are visible tissue-level folds, microvilli are membrane-level folds on the surface of a single cell. Name the correct one for the level the question is asking about.
2high涉及分数: 1Calculations
Rate calculations from practical data are given without units, or with an incorrect unit abbreviation, even when the number itself is correct.
如何避免: Decide what the answer's unit should be before you calculate, usually a volume or count per unit time, and write that unit next to the final answer every time.
3medium涉及分数: 1Graph drawing
Enzyme kinetics and pH graphs are drawn with a smoothed curve where the question specifies straight point-to-point lines between the plotted points.
如何避免: Check the instruction for the specific graph before drawing. If point-to-point lines are specified, use a ruler between consecutive points rather than a freehand curve.
4high涉及分数: 2Osmosis and water potential
Water movement is explained by saying water moves toward the higher sugar concentration, without ever stating the water potential gradient in terms of higher or lower, less negative or more negative.
如何避免: Always phrase water movement in terms of water potential: water moves from a region of higher, less negative, water potential to a region of lower, more negative, water potential.
5medium涉及分数: 1Microscopy and calculations
Magnification calculated from a scale bar or eyepiece graticule divides the measured length by the magnification before converting the length to micrometres, giving an answer wrong by a factor of a thousand.
如何避免: Convert the measured length to micrometres first, then divide by the magnification, in that order every time.
6medium涉及分数: 1Transport in plants
Water movement across the root cortex to the endodermis is explained without mentioning the Casparian strip, so the switch from the apoplast to the symplast pathway is left unexplained.
如何避免: Name the Casparian strip specifically as the waterproof, suberin-containing barrier that blocks the apoplast pathway at the endodermis and forces water into the symplast.
7low涉及分数: 1Cell physiology
Pressure potential is described for an animal cell as if it had one, ignoring that animal cells have no cell wall and so cannot generate wall pressure.
如何避免: Remember that pressure potential only applies to walled cells such as plant cells. An animal cell placed in a hypotonic solution swells and eventually lyses rather than becoming turgid.
8medium涉及分数: 1The circulatory system
Pressure changes during the cardiac cycle are described without linking each change directly to the opening or closing of a specific named heart valve.
如何避免: For every pressure change you describe, name the valve that opens or closes at that point and state why the pressure difference causes it to do so.