Estimating Populations & Sampling Reliability

What is abundance?

The number of individuals of a species in a given area.

What is distribution?

The pattern of where a species is found within a habitat.

What is population density?

The number of individuals per unit area or volume.

Why is it impractical to count every organism in a large habitat?

It would be too time-consuming and difficult.

Why is a representative sample important?

It allows results to be generalised more accurately to the whole habitat.

What is sampling bias?

A systematic error caused by selecting unrepresentative samples.

How can sampling bias be reduced?

By using random sampling and a consistent method.

What is a random error in ecological sampling?

Unpredictable variation between measurements or sample locations.

What is a systematic error in ecological sampling?

An error that consistently shifts results in one direction.

Why does increasing sample size improve reliability?

It reduces the influence of random variation and unusual samples.

What is an anomalous result?

A result that does not fit the overall pattern.

What should be done with anomalous results?

Investigate possible causes before deciding whether they should be excluded.

Why should sampling methods be standardised?

So differences in results are less likely to be caused by changes in technique.

Why is it useful to repeat sampling on different days?

To identify variation caused by changing environmental conditions.

What is the difference between accuracy and precision?

Accuracy means closeness to the true value, while precision means closeness of repeated measurements to each other.

Why should ecological conclusions acknowledge uncertainty?

Estimates are based on limited samples and naturally variable ecosystems.

How can an ecological investigation be made more valid?

By measuring the intended variable while controlling other relevant factors where possible.