rp12 Investigation into the effect of a named environmental factor on the distribution of a given species.

Describe how you could investigate the effect of an environmental factor on the distribution of a species in a habitat (random sampling in two areas)

1. Divide two areas into grids / squares eg. place 2 tape measures at right angles

2. Generate a pair of coordinates using a random number generator(eg. on a calculator)

3. Place a quadrat here and count number / frequency of [named species]

○ Standardise this eg. only count it if it is more than half in the quadrat

4. Repeat a large number of times (10 or more) and calculate a mean per quadrat for both areas

5. Measure environmental factor in each area eg. take soil moisture readings with a soil moisture meter

variables

Type	Description
Independent	Light intensity (abiotic factor)
Dependent	% cover of daisy plants
Control	Time of day/year, same species sampled, soil type/pH

why percentage cover may be used

rather than frequency.

difficult to count individual organisms /

individual organisms are too small to count

Explain why random sampling is used. (1)

avoid sampling sampling bias

Explain the importance of a large sample size.

● Minimises Minimises the effect of anomalies

● Ensures Ensures sample is representative of the population

Describe how you could decide the number of quadrats that should be used in order to collect representative data.

● Calculate Calculate a running mean

● When enough quadrats, quadrats, this shows little change

● Enough to carry out a statistical test