Determining the numbers of organisms in the habitat

When quadrats are used to randomly sample an area, it is important to scale up the results to know the numbers of organisms in the whole of the habitat. It is the best estimate that can be obtained, without spending hours and hours counting every single organism.

These results were obtained from a random study of a meadow, counting the number of dandelions. Random coordinates were generated ten times.

Quadrat number12345678910
Dandelion count4520153253

Scaling up the results

Step 1 - Calculate the mean number of dandelions per quadrat.

Mean = 4 + 5 + 2 + 0 + 1 + 5 + 3 + 2 + 5 + 3 = \frac{30}{10} = 3 dandelions per quadrat.

Step 2 - Calculate the total area of the quadrat. If the quadrat is 0.5 m by 0.5 m, the area is 0.5 × 0.5 = 0.25 m2.

Step 3 - Find the total area of the habitat being sampled. For example, if the meadow measured 10 m by 10 m, then its total area is 10 m × 10 m = 100 m2.

Step 4 - Divide the total area of the habitat by the area of one quadrat.

\frac{100}{0.25} = 400. This gives you the total number of quadrats that could fit into the habitat.

Step 5 - Multiply the average number of dandelions per quadrat by the total number of quadrats that can fit into the habitat.

3 × 400 = 1200. This gives you the estimated total number of dandelions in the meadow.