Sampling techniques and the measurement of abiotic and biotic factors
Previously we learnt about abiotic factors that could affect biodiversity What is the definition of an abiotic factor? A non-living factor in an ecosystem that can effect organisms. What are some abiotic factors in an ecosystem? Light intensity, temperature, pH and soil moisture
Previously we learnt about biotic factors that could affect biodiversity What is the definition of a biotic factor? A living factor in an ecosystem that can effect organisms. • What are some biotic factors in an ecosystem? Predation, competition, diseases
Today we are learning about • how abiotic factors can be measured • and errors avoided when measuring • them • how to use a quadrat and pitfall traps • to assess the numbers of organisms in • an ecosystem
Abiotic factors include light intensity, temperature, pH and soil moisture. These are easy to measure using simple equipment. Link the abiotic factor with the equipment used to measure it? • Light intensity moisture meter • Temperature pH probe or meter • pH thermometer • Soil moisture light meter
Easy! The teacher will now explain how to use the Equipment for measuring abiotic factors, how to avoid errors when using the equipment and any limitations there might be with the technique. (Most of this is a re-cap of work done in S1 Science)
Light intensity • Select the correct position if the meter has a switch • Put the meter in the area to be measured pointing the sensor area at the source of light • Read the correct scale and repeat a number of times for the area.
The ERRORS to be avoided include correct switch position and NOT shading the sensor. • The limitation is that light intensity changes with day time and cloud cover.
For which group of organisms might light intensity be most important? • Why might light intensity be important to these organisms?
pH and soil moisture (Often measured by the same meter) • Select the correct position if the meter has a switch. • Put the probe in the area to be measured, covering • only the tip. • Read the correct scale, • wipe the probe and • repeat a number of • times for the area.
The ERRORS to be avoided include correct switch position and wiping the probe • after each measurement is taken. • Not wiping the probe • will give a false reading.
For which group or groups of organisms might pH of their environment or soil moisture be important? • Why might pH or soil moisture be important to these organisms?
Temperature • Put the thermometer • in the ground or water • and leave for the heat • to take effect. • Read the scale and carefully, wipe the thermometer and repeat a number of times for the area.
For which group or groups of organisms might the temperature of their Environment be important? • Why might temperature be important to these organisms?
The abundance of animals and plants in an area can be estimated using a number of sampling techniques including quadrats and pitfall traps. These techniques only give an estimate representative sample and only if enough replication is carried out.
Quadrats • These are a square frame sub-divided • into smaller squares. • They are often 0.5m by 0.5m divided into • 25 smaller squares but can be much • smaller or bigger depending on the study • area. • They can be used in a random manner • or along a transect line.
Quadrats • These are a square frame sub-divided • into smaller squares.
Quadrats used randomly to get an overall abundance in an area. • Quadrats used on a transect line to help understand the changes in plants in a specific area.
Quadrats • These give a representative sample • in a small area. • Enough samples must be taken in relation • to the size of area studied. • They can be used to generate results for • a larger area.
Pitfall traps These are used to collect samples of small organisms moving along the surface of the soil. Dig a hole and place a pot in it, level with the ground. Put on a cover (stone) and leave overnight. Check for organisms the next day.
Pitfall traps • Only useful for small organisms. • Some organisms may eat others. • Organisms need to be identified • It gives a representative sample of the area.
What have you learned today? • Explain the meaning of abiotic factor? • What are 4 typical abiotic factors? • How can these factors be measured? • What errors can be made measuring them? • Explain the meaning of biotic factor? • What are 2 techniques used to sample organisms • in an area.