OCR · A-Level · Biology
Course version: H420 · Version from Sept 2025
Use of apparatus and techniques: (k) use of sampling techniques in fieldwork
Fieldwork sampling means choosing and applying a method that estimates a population or distribution without counting every individual.
Checked against the OCR H420 specification (opens in a new tab) on .
- Point 13 of 14
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Fieldwork sampling means choosing and applying a method that estimates a population or distribution without counting every individual. You should be able to use quadrats to sample sessile organisms, placing them randomly, for example by generating random coordinates within a grid, and to use a transect to record how distribution changes along an environmental gradient. For mobile animals, mark-release-recapture can be used, with the assumption that marked individuals mix randomly and are not affected by marking. You should also be able to use appropriate apparatus such as a pooter, sweep net or pitfall trap safely and record data systematically. Sampling is assessed by observing you carry out the technique and by the quality of the data you record, not by describing it in writing alone.
What earns the marks
- Selects a sampling method suited to the organism and question, such as quadrats for sessile organisms or a transect along a gradient.
- Places quadrats randomly, for example using random coordinates, to avoid bias in the sample.
- Uses apparatus such as a pooter, sweep net or pitfall trap correctly and safely to collect mobile invertebrates.
- Records data systematically and consistently, for example species present, counts or percentage cover, so results can be analysed.
Common mistakes and how to put them right
Placing quadrats where the habitat looks interesting.
Put it right: Correct practice uses random coordinates so the sample is unbiased.
Treating mark-release-recapture as a direct count.
Put it right: It is an estimate that relies on assumptions such as random mixing of marked individuals.
Recording data inconsistently, for example mixing counts and percentage cover.
Put it right: Correct practice uses one defined measure throughout.
Exam tips
- Link each sampling method to the type of organism and the question being asked, for example quadrats for plants and traps for invertebrates.
- State the assumption behind mark-release-recapture when explaining why the estimate may be inaccurate.
- Practise recording data in a clear table during fieldwork so the method and results can be reviewed afterwards.
Try the lesson
The start of the Use of apparatus and techniques: (k) use of sampling techniques in fieldwork lesson, made from checked teaching notes for this specification point.
Have a go first
When using a pooter to collect small insects from a leaf, which practice keeps the sample and the student safe?
Listen
Fieldwork sampling means choosing and applying a method that estimates a population or distribution without counting every individual. You should be able to use quadrats to sample sessile organisms, placing them randomly, for example by generating random coordinates within a grid, and to use a transect to record how distribution changes along an environmental gradient. For mobile animals, mark-release-recapture can be used, with the assumption that marked individuals mix randomly and are not affected by marking. You should also be able to use appropriate apparatus such as a pooter, sweep net or pitfall trap safely and record data systematically. Sampling is assessed by observing you carry out the technique and by the quality of the data you record, not by describing it in writing alone. A strong answer earns marks for these points. Selects a sampling method suited to the organism and question, such as quadrats for sessile organisms or a transect along a gradient. Places quadrats randomly, for example using random coordinates, to avoid bias in the sample. Uses apparatus such as a pooter, sweep net or pitfall trap correctly and safely to collect mobile invertebrates. Records data systematically and consistently, for example species present, counts or percentage cover, so results can be analysed. Exam tip: Link each sampling method to the type of organism and the question being asked, for example quadrats for plants and traps for invertebrates.
Key words
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Random sampling with quadrats
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Transects along environmental gradients
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Mark-release-recapture for mobile animals
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Systematic data recording and apparatus safety
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See every definition
- Random sampling with quadrats
- Placing quadrats randomly, for example by generating random coordinates within a grid, to avoid bias in the sample.
- Transects along environmental gradients
- Using a transect to record how distribution changes along an environmental gradient.
- Mark-release-recapture for mobile animals
- A method for mobile animals that relies on assumptions such as marked individuals mixing randomly and not being affected by marking.
- Systematic data recording and apparatus safety
- Using apparatus such as a pooter, sweep net or pitfall trap safely and recording data systematically and consistently so results can be analysed.
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