1.2 Investigating Populations

Quadrats
3 factors to consider:

Size of quadrat - depends on size and distribution of organisms
Number of quadrats - the larger the number, the more reliable the results. Need balance between validity and time available.
Position of quadrat - Random sampling

Random Sampling

Lay out two long tape measures at right angles, along two sides of the study area.
Obtain a series of coordinates by using random numbers taken from a table or generated by a computer.
Place a quadrat at the intersection of each pair of coordinates and record the species within it.

Systematic sampling along transects

Sometimes more informative to measure abundance and distribution in a systematic rather than a random manner.
Particularly important where some form of transition in the communities of plants and animals takes place.
Line transect - tape stretched along ground, any organism on the line is recorded.
Belt transect is a strip, 1m wide, marked by putting a second line parallel to the first, species within the lines are recorded.

Measuring abundance

The number of individuals of a species within a given space.

Can be measured in a number of ways including:

Frequency -

	Created by Jody Lelean-Smith about 10 years ago

Biology Note on Populations, created by Jody Lelean-Smith on 14/02/2014.

Populations