The number of individual plants – The pupil counts the number of individual plants of the selected species in each quadrat. The result can be expressed as number of plants per square metre. This measure is known as density.

## How do you calculate the quadrat?

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 m 2. Step 4 – Divide the total area of the habitat by the area of one quadrat. = 400. This gives you the total number of quadrats that could fit into the habitat.

What are the two types of quadrat?

Modern quadrats can for example be rectangular, circular, or irregular. The quadrat is suitable for sampling plants, slow-moving animals, and some aquatic organisms.

A transect is a line across a habitat or part of a habitat. A quadrat has been placed at regular intervals of a metre (or a few metres) along the transect. A gradual change in the distribution of species across a habitat is called zonation.

A quadrat is often used to sample plants. It marks off an exact area so that the plants in that area can be identified and counted.

### How does Quadrats size affect estimate of density?

Other things being equal, it is apparent that if a sample quadrat is enlarged, it may overlap part of the range of some species previously not present and thus will increase the measured species density.

What is a drawback of transects?

Displaying the data collected in line transect diagrams also becomes easier because the horizontal scale can be adjusted to fit smaller sheets of paper. The disadvantage in this case is that many of the species present may be overlooked if the interval selected is too large.

## What do quadrats help us investigate?

Using a quadrat The organisms underneath, usually plants, can be identified and counted. Quadrats may also be used for slow-moving animals, eg slugs and snails.