Abiotic Factors

• Abiotic factors are non-living variables that influence where organisms can live.
• Abiotic factors include: light intensity, temperature, soil PH, soil moisture, humidity etc.
• A biotic factor is an interaction associated with a living organisms. This can also influence how organisms are distributed.
• Examples of biotic factors include: competition, disease, grazing, predation etc.
• Temperature is measured with a thermometer but an error can be caused when the thermometer takes a temperature but not in the sample area (removed too quickly). You can fix this by keeping the thermometer in the sample area when taking the reading.
• Light intensity is measured with light meter but an error can be caused when the person measuring casts a shadow over the light sensor on the meter. You can fix this by not standing between the sensor and the light source.
• Soil moisture is measured with a moisture meter but an error can be caused if The probe on the meter is not clean/ is covered in soil from previous samples. You can fix this by wiping the probe between samples.
• Soil PH is measured with a PH meter but an error can be caused by the probe on the meter being not clean. You can fix this by wiping the probe between samples.
• A pitfall trap is a cup with holes in the bottom for drainage that is level with the soil and is covered with a plank on stones. Bugs fall into the trap allowing you to see what bugs are in the area.
• A source of error in a pitfall trap is that it may not be representative of all the bugs in the area so you can minimise this by taking many samples.
• A source of error in a pitfall trap is that The animals may be eaten by birds so this is why you cover it with a plank
• A source of error in a pitfall trap is that Larger bugs may eat the smaller ones. You can minimise this by checking the trap regularly or using a preservative solution that kills the bugs as soon as they fall in.
• Quadrats are used to sample plants or slow moving animals.
• Quadrats can be used to estimate total numbers or measure abundance.
• A source of error for a Quadrat is incorrect counting. To minimise this count only plants where half or more is inside the Quadrat.
• A source of error for a Quadrat is not enough sample thrown. To minimise this you should throw more Quadrats to get more reliable results.
• A paired statement key is a series of questions or statements with two possible answers.
• To follow a pair statement key you start at question one and follow the instructions until the organism has been identified.
• A line transect is a line across a habitat where samples are made at intervals. This allows us to find a trend or linear pattern of how organisms are distributed.
• An indicator species is a species who’s presence or absence indicates the pollution levels or quality of the environment. e.g. a sludge worm lives in highly polluted water so if there are many of them then the water is very polluted.