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 This exercise allows you to use the quadrat sampling method to measure the biodiversity of plants or invertebrates in your garden, school playing field or local park. You should do these exercises under the supervision of your teacher or an adult.  A quadrat is a square frame. Many biologists use a quadrat with 30 cm sides. You can make your own quadrat with a plastic ruler, string and four tent pegs.  Tie five knots in the string at 30cm intervals. Then tie the two end knots together to form a loop of string. To set out your quadrat, pull the string into a square with a knot at each corner, and peg the corners to the ground with the tent pegs. All the types of plant or invertebrate that occur in your playing field, park or garden will not be found in one 30 cm quadrat. Putting your quadrat in ten different places will give you a better estimate of the biodiversity. However, do not choose what you think are the "best" places to put your quadrat because this will bias your sample. To make the sample random, throw the ruler over your shoulder and peg out the string quadrat where the ruler lands. To measure invertebrate biodiversity  Invertebrates are very common in the leaves, twigs and rotting vegetation that accumulates under trees in woodlands, or under hedge rows. You can measure the invertebrate biodiversity using the string quadrat (see above for details on how to make this), a pair of gardening gloves, a large plastic tray and a small paintbrush.  Randomly place your quadrat and peg out the four corners. Wearing gardening gloves, gently scoop-up the leaf-litter, small twigs and loose humus from inside the quadrat and place in the tray.  Carefully separate all the leaves and twigs in the tray,and use the paintbrush to sort through all the debris. Identify all the different types of invertebrates you see.  You may find ants, beetles, woodlice, spiders, centipedes, millipedes, snails, slugs and earthworms. You can also count all the individuals of each kind of animal you find.  After you have finished with each quadrat, remember to return all the animals and the leaf-litter to where you collected them.Draw a graph of the invertebrate biodiversity, in the same way you would the graph for plant biodiversity (see below). Are your two graphs the same shape? Are ten quadrats enough to get a good estimate of invertebrate biodiversity? If you have counted the number of individual animals of each kind, calculate the average number of animals per quadrat. What type of animal is the most common? By using the quadrat sampling method you can compare the biodiversity in different areas. This will help to reveal ecological differences between sites. To measure plant biodiversity  Count the number of different types of plant growing in each quadrat.To help you identify each type of plant, draw a picture of each type. The colour and shape of the flowers and leaves will help you to identify what plants are growing in each quadrat. Give each plant type a name or code letter. When you have finished the ten quadrats, plot the plant biodiversity on a graph. To do this, first calculate the cumulative total of different plant types found in each quadrat (follow the example in the table below). Plot the cumulative total of plant types against each quadrat to draw your graph.
 Look at the graph given here as an example. When the line of your graph stops rising it means you have probably recorded most of the biodiversity in the area where you took your quadrat samples. How does your graph compare with this one? Is your graph beginning to flatten off after 10 quadrats? If your graph is still rising, what does it mean? What will your graph look like if you sample twenty quadrats? More biodiversity activities Do you want more information on biodiversity, and to do more fieldwork? If so, visit the Natural History Museum’s site called "Exploring Biodiversity" at http://www.nhm.ac.uk/eb/ Do you want to learn about woodlice? Do you want to take part in a national project to map the geographical distribution of Britain’s species of woodlice? Then go to the Natural History Museum’s site called "Walking with woodlice" at http://www.nhm.ac.uk/woodlice/ Go back |