Measuring Organism Abundance and Distribution Flashcards

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What does 'abundance' of a species mean?

The number of individuals in a given area, often per square metre (m^2).

What does 'distribution' of a species mean?

Where a species is found across a habitat or area.

What is a quadrat and what is it used for?

A square frame of known area. It is used to sample organisms.

Why should quadrats be placed at random?

To avoid bias and get a fair, representative sample.

How can you place quadrats at random using coordinates?

Lay two tape measures at right angles. Use random numbers to pick distances along each tape. Place the quadrat at that point.

What is percentage cover and when is it used?

The percentage of the quadrat area covered by a species. Use it when counting is hard.

How do you estimate population size from quadrat data?

Find the mean number per quadrat. Divide by quadrat area for density. Multiply by total area.

What is a belt transect used for?

To show how abundance changes along a line, for example from shade to sun.

How do you carry out a belt transect?

Lay a tape across the area. Place quadrats at set distances. Record counts or percentage cover.

Why repeat your samples and calculate a mean?

To improve reliability and reduce the effect of chance.

How do you avoid double-counting on a quadrat edge?

Count those on the top and left edges only, not the bottom or right.

Which unit is used for density in these studies?

Number of individuals per square metre (m^2).