National 5 Biology Course Notes Unit 3 : Life on Earth Part 3 : Sampling techniques and measuring abiotic factors

Quadrat It is used to sample the abundance of plants or very slow moving animals in an area The number of squares containing the organism is counted to give a measure of its abundance. The quadrat must be thrown at random and the results from several quadrats are taken and an average taken to make the result more reliable. Pitfall trap A pitfall trap is a container, for example a plastic cup which is buried in the soil with it’s rim level with the soil surface. A quadrat is a square frame divided into smaller squares It is used to collect and sample invertebrates crawling on the soil surface Several pitfall traps should be set up to make the result more reliable. Errors may occur when using pitfall traps because: Insects that can fly may escape from the traps Some predators that are trapped may eat other trapped invertebrates

Measuring abiotic factors Abiotic factorInstrument used to measure abiotic factor Steps taken to reduce error when measuring Light intensityLight meter Hold the meter away from your body to ensure you are not shading the meter Soil moistureMoisture meter Wipe the meter probe dry after each measurement Make sure the probe is deep enough in the soil pH meter Soil pH Clean the meter probe between readings