Field Investigations
Field Investigations GCSE Biology Practical
Measuring population size of a common species in a habitat using sampling techniques to investigate the species.
This is a two-part investigation in which students are required to measure the population size of a plant species using random sampling and then investigate the e4ect of a factor on plant distribution using a transect line. Light intensity is a good factor to measure using a light meter. An outdoor survey area of around 400m² is required for a class of students and should be prepared by marking out a 20M x 20M square for each group using string and a trundle wheel or tape measure. Students should also be familiarised with the identification of the plants which are being counted.
Equipment (per pair of participants)
• 1 x quadrat
• 1 x tape measure or 1 x trundle wheel
• 1 x light meter
• 1 x clipboard
• 2 x bags of numbers 1M-20M
Method
Basic Quadrat Sampling
- Setup
- Before the practical session, mark a 20m x 20m square on the ground using a trundle wheel and string.
- Random Coordinate Selection
- Provide two bags containing numbered cards (e.g., color-coded for clarity).
- Each group member selects one number from each bag. These numbers represent the coordinates for quadrat placement.
- Positioning the Quadrat
- One student walks the first coordinate distance (in meters) along the base of the 20m square and stands there.
- Another student measures the second coordinate distance up the side of the square and stands at that point.
- A third student places the quadrat where the two coordinates intersect within the 20m square.
- Data Collection
- Count and record the number of individuals of the chosen plant species within the quadrat.
- Use a light meter to measure and record the light intensity at this spot.
- Repetition
- Return the numbered cards to their respective bags.
- Repeat the process for ten quadrats.
- Population Size Calculation:
- Use the following equation to estimate population size:
Transect Line Method
- Preparation
- Identify the plant species to study.
- Stretch a 30m tape measure from the base of a tree to create the transect line.
- Data Collection Along the Transect
- Place a quadrat with one corner aligned to the zero mark on the tape measure.
- Count the number of the chosen plant species within the quadrat and record the data in a table.
- Measure and record the light intensity at this spot using a light meter.
- Systematic Sampling
- Move the quadrat along the tape measure at regular intervals (e.g., every 2m or 5m).
- Repeat the process, counting the plants and measuring light intensity at each interval, until the entire 30m transect has been surveyed.
Technician tips
• The 20M square can be marked out for the students just before the start of the lesson to save time.
• The two bags of numbers could be made from different coloured paper, in order to assist with the students returning them to the correct bags
To do this practical you will need
Need some Biology inspiration and help?
Measure and sample species in a habitat for GCSE Biology practicals by using our required method and sampling equipment. For students to do this practical they will need grid quadrats, tape measures, trundle wheels, light meters and clipboards. Browse and explore our site for more science equipment ideal for schools or lab experiments.
