Sampling techniques and the measurement of abiotic and biotic factors

Previously we learnt about abiotic factors that could affect biodiversity

What are some abiotic factors in an ecosystem?

Light intensity, temperature, pH and soil moisture

What is the definition of an abiotic factor?

A non-living factor in an ecosystem that caneffect organisms.

Previously we learnt about biotic factors that could affect biodiversity

What are some biotic factors in an ecosystem?Predation, competition, diseases

What is the definition of a biotic factor?A living factor in an ecosystem that caneffect organisms.

Today we are learning about

• how to use a quadrat and pitfall traps to assess the numbers of organisms in an ecosystem

• how abiotic factors can be measured and errors avoided when measuring them

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

• Read the correct scale and repeat a number of times for the area.

• Put the meter in the area to be measured pointing the sensor area at the source of light

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)

• Read the correct scale, wipe the probe and repeat a number of times for the area.

• Put the probe in the area to be measured, covering

only the tip.

• Select the correct position if the meter has a switch.

The ERRORS to be avoided include correct switch position and wiping the probeafter each measurement is taken.

Not wiping the probewill give a false reading.

For which group or groups of organisms might pH of their environmentor soil moisture be important?

Why might pH or soil moisture be important to these organisms?

Temperature

• Read the scale and carefully, wipe the thermometer and repeat a number of times for the area.

• Put the thermometer in the ground or water and leave for the heat to take effect.

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 plantsin an area can be estimated using a numberof sampling techniques including quadrats and pitfall traps.

These techniques only give an estimaterepresentative sample and only ifenough replication is carried out.

Quadrats

They can be used in a random manneror along a transect line.

They are often 0.5m by 0.5m divided into25 smaller squares but can be much smaller or bigger depending on the studyarea.

These are a square frame sub-divided into smaller squares.

QuadratsThese 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.

QuadratsThese give a representative samplein a small area. Enough samples must be taken in relationto the size of area studied.

They can be used to generate results fora 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 organismsthe next day.

Pitfall traps

It gives a representative sample of the area.

Organisms need to be identified

Some organisms may eat others.

Only useful for small organisms.

What have you learned today?

Explain the meaning of biotic factor?What are 2 techniques used to sample organismsin an area.

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?