Sampling techniques and the measurement of abiotic and biotic factors

Previously in S1 you learned about abiotic factors that could affect organisms What is the definition of an abiotic factor? A non-living factor in an ecosystem that can effect organisms and their distribution. What are some abiotic factors in an ecosystem? Light intensity, temperature, pH and moisture

Previously in S1 you learned about biotic factors that could affect organisms What is the definition of a biotic factor? A living factor in an ecosystem that can effect organisms and their distribution. What are some biotic factors in an ecosystem? Predation, competition, grazing, diseases, food availability

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 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 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 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?

Sampling Animals and Plants 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 to camouflage it. Leave overnight. Check for organisms the next day.

Pitfall traps Only useful for small organisms. Do not leave too long 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 4 typical biotic factors? What are 2 techniques used to sample organisms in an area. What errors can be made measuring them?

Average Moisture reading Quadrat Average Moisture reading Average light reading Ave. pH of soil Abundance of plant (0 – 25) Dandelion Clover Plantain Daisy Grass 1  5 2000     0  23 14  0   25 2  3.5 2000  7  10 25 3  1.5  12  3 4  20  9 5  2 6  4  18 7  1 8 9  6 10

Average Moisture reading Quadrat Average Moisture reading Average light reading Ave. pH of soil Abundance of plant (0 – 25) Dandelion Clover Plantain Daisy Grass 1 4  2000  8  0  24 12   3  25 2  4  14  17 3  6  5  1  7.5  20 5  15 6  5.5 7  9 8  7 9  2 10