Required Practical 12 - Sampling with a named environmental factor
Laura Armstrong
Teacher
Recall Questions
This topic requires prior knowledge of abiotic and biotic environmental factors, ecological sampling techniques, and interpretation of species distribution. You can test your knowledge on these below.
What is an abiotic factor?
A non-living environmental variable, such as light intensity, temperature, soil pH, or moisture.
What is a belt transect used for?
To measure changes in species distribution across a gradient, typically alongside a changing environmental factor.
Why is random sampling not suitable for investigating changes along a gradient?
Because it does not allow for analysis of how species distribution varies with a directional change.
Objective of the Practical
To investigate how an abiotic factor affects the distribution or abundance of a species using a systematic sampling method (belt transect).
Equipment List:
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Tape measure (20m+)
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Quadrat (0.25 m² or 1 m²)
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Light meter (or alternative abiotic sensor)
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Identification key (if needed)
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Calculator or data logger
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Clipboard and recording sheet
Example Investigation
Research Question: Does light intensity affect the percentage cover of daisy plants across a grassland/woodland boundary?
No answer provided.
Method
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Lay out a transect:
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Place a measuring tape in a straight line from the shaded area (e.g., woodland) to an open area (e.g., grass field).
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This defines the environmental gradient.
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Sample along the transect:
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Place a quadrat at regular intervals (e.g., every 2 metres).
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Within each quadrat, estimate % cover of the target species (e.g., daisies).
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Use the light meter to record light intensity at each quadrat point.
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Repeat:
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Repeat the transect in other locations parallel to the first.
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Calculate mean percentage cover at each distance along the transect.
Data Analysis
- Plot a scatter graph of % cover vs. light intensity.
- Use Spearman’s Rank Correlation Coefficient to test the relationship. This will tell us if there is a correlation and if so, if it is significant.
Expected Outcomes
- In many habitats, plant species will have a preferred light range.
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For example, daisy cover may increase with light intensity up to a certain point, then plateau or decrease.
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Competition amongst plant species will affect growth and distribution and some species may be better adapted to grow in lower light intensities.
Variables
|
Type |
Description |
|
Independent |
Light intensity (abiotic factor) |
|
Dependent |
% cover of daisy plants |
|
Control |
Time of day/year, same species sampled, soil type/pH |
Key Terms
- Transect: a line across a habitat to investigate changes in species across a gradient.
- Abiotic factor: a non-living environmental influence.
- Percentage cover: an estimate of the area a species occupies within a quadrat.
- Systematic sampling: sampling at regular intervals along a transect.
No answer provided.
Exam Tips
Remember to measure the abiotic factor at each quadrat point
Justify why you used a systematic approach rather than random sampling.
Evaluate reliability: Did you use enough quadrats? Did you use repeat transects? Did weather conditions vary during sampling?
No answer provided.
Describe how you would investigate the effect of light intensity on the distribution of buttercups across a school field. (5 marks)
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Lay a tape measure across the field from a shaded area to a sunny area.
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Place a quadrat at regular intervals (e.g., every 2 metres) along the transect.
- Use a large number of quadrats.
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In each quadrat, record the percentage cover of buttercups.
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At each point, use a light meter to record light intensity.
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Analyse the relationship using a scatter graph or Spearman’s Rank.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!