AQA GCSE Combined Science Biology Required Practicals

Paper 2 Required Practical's

how do you conduct the photosynthesis practical

• Place pondweed in beaker of water.

• Use a light source at varying distances.

• Count number of bubbles per minute (oxygen production).

• Repeat at different distances.

what is the independent variable of the photosynthesis practical

Light intensity (distance of lamp).

what is the dependant variable of the photosynthesis practical

Rate of photosynthesis (bubbles/min).

what are the control variables of the photosynthesis practical

• Same type/length of pondweed

• Temperature

• CO₂ concentration (can add sodium hydrogen carbonate)

what are the limitations of the photosynthesis practical

• Counting bubbles is not very accurate

• Light intensity drops off rapidly with distance (inverse square law)

what are common errors of the photosynthesis practical / tips for exam questions

• Use ruler to measure distance from light

• Could use gas syringe for more accurate measurement

how do you conduct the ruler drop test

• One person holds a ruler vertically between the volunteer’s thumb and finger.

• Without warning, release the ruler.

• Record the distance the ruler falls before being caught.

• Repeat and average.

what is the independent variable for the ruler drop test

Condition (e.g., caffeine, distraction).

what is the dependant variable for the ruler drop test

Reaction time (distance ruler falls).

what are the control variables for the ruler drop test

• Same ruler

• Same tester

• Same start position

• Avoid practice effects

what are the limitations of the ruler drop test

• Human error in catching

• Reaction time affected by tiredness or distraction

what are common errors of the ruler drop test / tips for exam questions

• Convert distance to time using a chart or formula

• Avoid giving cues before dropping the ruler

how do you conduct the field investigation (quadrats and transects)

• Place a quadrat randomly (or at regular intervals along a transect).

• Count number of organisms (e.g., daisies).

• Repeat at multiple points.

• Calculate mean and estimate population size or distribution pattern.

what is the independent variable of the field investigation

Location/distance along the transect.

what is the dependant variable of the field investigation

Number or type of organisms.

what are the control variables of the field investigation

• Quadrat size

• Time of day

• Sampling method

what are the limitations of the field investigation

• May not represent whole area

• Organisms may be missed or misidentified

what are common errors in the field investigation / tips for exam questions

• Know how to calculate mean, percentage cover, and population estimate

• Use correct fieldwork terminology