1. A area of woodland with some small plants growing in the ground between the trees - Edexcel - GCSE Biology Combined Science - Question 1 - 2021 - Paper 1

As light intensity increases, the number of small plants per square meter generally increases. This is because higher light levels promote photosynthesis, which enables plants to grow more effectively and compete for resources. From the data provided, areas with higher light intensity, such as Area A (1500 lux), support a greater number of small plants compared to areas with lower light intensity, like Area F (350 lux), which has only 0.1 small plants per m².

One variable that should be controlled is the time of day when measurements are taken, as light intensity can vary significantly at different times.

To use a belt transect, the scientist should first select a starting point and lay a tape measure along the transect line. Along this line, quadrats can be placed at regular intervals (e.g., every meter) to sample the growth of stinging nettles. At each quadrat, the light intensity can be measured using a light meter. Additionally, the density or height of the stinging nettles should be recorded at each quadrat. This method enables the scientist to correlate light intensity measurements with the growth conditions of stinging nettles, providing insights into their environmental preferences.