A transect is a line across a habitat or part of a habitat. It can be as simple as a string or rope placed in a line on the ground. The number of organisms of each species along a transect can be observed and recorded at regular intervals.

The distribution of organisms in a habitat is affected by the presence of other living organisms - such as herbivores or carnivores - that might eat them. It is also affected by abiotic factors, such as availability of light or water.

A kite diagram shows the number of animals (or percentage cover for plants) against distance along a transect.

Kite diagram showing grasses and dandelions over 25m. Grasses rise slightly and fall slightly over long period then rise and fall steeply to 25m. Dandelions rise steeply, then fall gradually to 20m.

In the example above, the distribution of dandelion plants gradually changes from five metres to 20 metres along the transect. 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. It can happen because of a gradual change in an abiotic factor.

A transect is usually used to investigate a gradual change in a habitat rather than to simply estimate the number of organisms within it.