GCE AS/A Level Biology Practical Assessment

How can we best prepare for coursework?

Candidates need…. Practice at making observations Practice at drawing biological material Practice at preparing tables Practice at drawing graphs Practice at evaluations

Observations Detailed Start at the beginning Record whole change (not just end result) Record observation (not an interpretation)

Drawings Sharp pencil Single clear lines – ‘seamless’ joins No shading (or colouring) Informative title Scale and/or magnification Low power tissue plan (no cells) High power cell detail Cells to scale – no ‘bubble’ shaped cells Invisible margin – drawing inside; labels outside Don’t cross label lines

Tables Informative title One table Independent or Input variable in left hand column and dependent or output variable to right Fully ruled, including a border….with a ruler Column headings. Make sure dependent title covers the repeats and mean columns. Units in headings SI units Observations in sequence, no conclusions inferences or ticks! All cells completed Usually no processed data (mean is ok)

Graphs Meaningful title – ‘A graph to show….’ Independent or input variable on horizontal x-axis Dependent or output variable on vertical y-axis Axes labelled Axes with units Full use of paper provided Plotted accurately (use a x) Straight lines between points unless certain intermediate values would fall on a curve

Students need to understand the key terms. Accuracy Anomalous Reliability Precision Validity Limitation

Students need to understand the key terms. Accuracy

Accuracy How close a reading or observation or measurement comes to the ‘true’ (or real) value or outcome. This could refer to: accuracy of measuring apparatus closeness of data points to a line of best fit

Students need to understand the key terms. Accuracy Anomalous

Anomalous an individual result or piece of data that does not match the trend shown by other results. if this result, after repeats, still appears to be ‘odd’ (as it does not match the repeats) then it should be considered to be anomalous. but what if the repeats are consistent with the original result?

Students need to understand the key terms. Accuracy Anomalous Reliability

Reliability a result or data may not always match the trend shown by other results. the reliability of this data can be measured by carrying out repeats and/or statistical tests (such as the mean or standard deviation). if an ‘odd’ result is confirmed to be sound by repeats, then it is not anomalous.

Students need to understand the key terms. Accuracy Anomalous Reliability Precision

Precision measurements or observations can vary in how exact or clearly stated they are (i.e. how precise they are). it could also refer to the number of decimal places that a number is expressed in. The size of the smallest scale division on the measuring device. (or half the smallest division)

Students need to understand the key terms. Accuracy Anomalous Reliability Precision Validity

Validity results, measurements or procedures vary in how well they actually measure or carry out what they are designed to do. inappropriate measurements or procedures could lead to conclusions that are not valid because they have not done what they set out to do. factors or variables that have not been controlled will also affect validity.

Students need to understand the key terms. Accuracy Anomalous Reliability Precision Validity Limitation

Limitation Any factor or variable that has not been considered or has not been controlled

Evaluation of procedure Sufficient repeats to make results reliable Sufficient range of input variable Sufficient number of readings at different inputs Control of other variables How to make the procedure more precise/valid/accurate/reliable

Evaluation of results Spotting a trend Identifying anomalous results Accounting for anomalous results Identifying unreliable means Explaining a trend

Practical Assessment - Task 1 Qualitative Task – 10 marks Perform the task competently, demonstrating skilful and safe practical techniques Wear safety glasses, be organised, deal with spillages, rinse apparatus before re-use etc Observe accurately Record reliably Organise observations Explain observations The qualitative task:Practically based Typically microscopy …..or test tube observations. May require some conclusions Out of 10

Where do candidates go wrong with observations? Students may: miss a series of observations and start their description too late (e.g. immobilised yeast) not be sufficiently descriptive e.g. not record differences in reaction (simply whether or not a reaction occurred) use the wrong term e.g. put ‘clear’ when they mean ‘colourless’ record conclusions/inferences rather than observations record final colour when asked to record colour change draw text book diagrams rather than what they can actually see

Practical Assessment - Task 2 Quantitative Task – 10 marks Use apparatus competently and safely Record accurate measurements Record results to an appropriate degree of precision Record reliably Organise results Analyse and interpret experimentally derived results to reach valid conclusions The quantitative task: Practically based Typically a timed enzyme experiment More meaty - out of 1o

Where do candidates go wrong with tables? Students may: use the wrong format for a table forget to put units in put units in the body of the table not identify independent (input) variable by putting it in the first column not ‘rule up’ tables especially the borders split tables

Where do candidates go wrong with graphs? Students may: draw the wrong type of graph put axes the wrong way around do not label axes use inappropriate scales do not give units or the units are incorrect incorrect trend lines

Practical Assessment - Task 3 Evaluative Task – 20 marks Process and interpret results, identifying anomalies and reaching valid conclusions Use scientific knowledge and understanding to suggest explanations for trends or patterns Assess the reliability and accuracy of an experimental task, identifying weaknesses in procedures Identify and explain main limitations of data collection strategy and give reasons for simple improvements Comment on reliability of the data and discuss the validity of the conclusions This extends the quantitative task - analysis of collected data and experimental situation - will not require further data collection Modifications need to be considered. Likely to be harder than other two task types Out of 20 Tasks and Mark schemes down loaded from interchange site. Practical skills handbook available – INSET support

Where do candidates go wrong with evaluations? Students may: fail to spot anomalous results incorrectly identify anomalous results be unable to suggest obvious improvements to the procedure be unable to suggest how to control other variables e.g. they may say ‘use a better thermometer’ when they mean ‘use a thermostatic water bath’ be unable to suggest how to make the measurements more precise e.g. ‘use a stop watch’ rather than ‘time from…until…’