Six legs Eight legs More than eight legs Segmented body Body not segmented
Insect, e.g. wasp Spider
Centipede or millipede
Worm, e.g. common earthworm Mollusc, e.g. snail
Fig. 11 A simple key to identify small invertebrates.
5. Observing and identifying plants present in the habitat There will usually be many different species of plants within your study area. It is not practical to record every individual plant present. We can get a good idea of which plants are present by observing a number of small sample areas within our study area. To do this we use a square frame called a quadrat. It is placed randomly in the study area and the types of plant within the quadrat are listed. The quadrat is used several times to give a more accurate record of which plants are present in the entire study area. The data that is collected using a quadrat can also be used
to estimate how much of a particular type of plant there is within the study area. To do this scientists calculate the percentage frequency for each type of plant as shown in Fig. 13. This is quantitative data. The quadrat is thrown at random 10 times. After each throw the species found in the quadrat are ticked off on the chart. The percentage frequency is then calculated as follows:
Fig. 12 A quadrat is used to estimate plant numbers.
Frequency = Species 1 2 Grass Brambles
Stinging nettle Ivy
Hogweed Wood sorrel a 170 3 Number of ticks Total number of quadrats 4 5 X
100 1
Quadrat number 6 7 8 9 10
a a a a a a a a a a 10 a
a a a a a a a
a 2 a 3 2 1 3
Fig. 13 The data collected using the quadrat can be presented in a table.
