Define the sampling area, select coordinates without bias, standardise observations and record enough locations, distances or environmental values for comparison.
The photograph shows part of a desert in Mexico.
A scientist observed that one species of cactus, Neobuxbaumia tetetzo, was often found near a species of tree, Mimosa luisana.
The scientist decided to test the hypothesis that the cactus plants often grow close to mimosa trees.
One hundred locations were selected at random. A quadrat was placed at each location.
The presence or absence of each species was recorded in each quadrat.
Abiotic variables in the soil cannot be controlled in this investigation. However, these variables can be measured to confirm that these plants are growing in similar conditions.
State two abiotic variables in the soil that could affect this investigation. First variable Second variable