11.3 sampling technique

What are the four sampling techniques required by OCR A Biology?

Quadrats, sweep nets, pitfall traps and pooters.

What is a quadrat?

A square frame used to sample organisms within a defined area.

Which organisms are quadrats commonly used to sample?

Plants and slow-moving or stationary organisms.

How are quadrats used in random sampling?

Place quadrats at randomly generated coordinates and record the organisms present.

How can abundance be measured using quadrats?

Count the number of individuals of each species within each quadrat.

How can percentage cover be estimated using quadrats?

Estimate the percentage of the quadrat occupied by a particular species.

What is a sweep net used to sample?

Invertebrates living in vegetation.

How is a sweep net used?

Sweep the net through vegetation to collect invertebrates.

What is a pitfall trap used to sample?

Ground-dwelling invertebrates.

How does a pitfall trap work?

A container is buried with its opening level with the soil surface, allowing ground-dwelling invertebrates to fall inside.

Why should pitfall traps be covered?

To prevent rain entering and reduce disturbance from larger animals.

What is a pooter used to collect?

Small insects and other invertebrates.

How does a pooter work?

Suction draws small organisms into a collecting container through a tube.

Why does a pooter have gauze in its mouthpiece tube?

To prevent the organism from being inhaled.

How can sampling techniques be improved?

Use a larger sample size, repeat sampling and use appropriate techniques for different organisms.

Why should different sampling techniques be used in a habitat?

Different techniques collect different types of organisms, increasing the range sampled.