Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

5.2.6Unit 5: Respiration, Internal Environment, Coordination and Gene Technology

Core Practical 11: Quadrat and Transect Study — IAL Edexcel Linear Revision Notes & Topical Questions

5 min read 6 parts Lesson 21 of 36 Unit quiz

📚 IAL Edexcel Linear Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read

Part 1 of 6Sampling Methods

5.2.6 Core Practical 11: Quadrat and Transect Study

It is usually impossible to count every organism, so a sample is taken.

Random sampling
  • Quadrat positions are chosen using random numbers, which avoids bias in where samples are placed.
Systematic sampling
  • Samples are taken at fixed intervals, such as every metre along a line.
Quadrat
  • A frame of known area, such as 0.25 m², placed on the ground to sample plants.
Sample size
  • More quadrats give a more reliable estimate and reduce the effect of unusual areas.

Part 2 of 6Measuring Abundance

Measuring Abundance
Frequency
  • The percentage of quadrats in which a species is present.
Density
  • The number of individuals per unit area.
Percentage cover
  • An estimate of the area covered by a species, useful for plants that are hard to count.
Estimate
  • Population size = mean number per quadrat x total area / quadrat area.

Part 3 of 6Using a Transect

A belt transect shows how species change along an environmental gradient.

1
Stretch a measuring tape in a straight line across the habitat, for example from the shore upwards.
2
Place the quadrat at set intervals along the tape and record the species present.
3
Measure abiotic factors such as light intensity, soil moisture and pH at each point.
4
Compare the changes in species with the abiotic factors, using a statistical test such as Spearman's rank correlation.

Part 4 of 6Reliable Results

Identification
  • Use a key and be consistent when identifying species.
Repeat
  • Repeat the study in other areas or at other times to check the results.
Environment
  • Avoid damage to habitats and wear suitable clothing, with permission to enter the site.
Limitations
  • Mobile animals are hard to sample this way, so other methods are needed.
MethodUse
Random quadratsEstimate abundance across an area
Belt or line transectStudy change along a gradient
Percentage coverPlants that are hard to count

Part 5 of 6Worked Example

Question

  • A field of 400 m² is sampled with 0.25 m² quadrats.
  • Mean count of daisies per quadrat is 3.5.
  • Estimate the population.

  1. Number of quadrat areas in the field = 400 / 0.25 = 1 600.
  2. Population = 3.5 x 1 600.
  3. = 5 600.

Answer About 5 600 daisies.

Part 6 of 6Exam Checklist & Tips

5.2.6 – Key Points for the Exam

  • Quadrat A square frame of known area used to sample organisms.
  • Transect A line or belt along which samples are taken to study change across a habitat.
  • Random sampling Choosing sample positions by chance to avoid bias.
  • Systematic sampling Sampling at regular intervals.

Common Mistakes

  • Throwing a quadrat over the shoulder and calling it random; use random coordinates.
  • Using too few quadrats for a reliable estimate.
  • Forgetting to measure the abiotic factors along the transect.
  • Mixing up the area of the quadrat and the total area when scaling up.

Last updated:

\n