rp 12

Question 1

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)

Answer 1

1. Divide two areas into squares eg. place 2 tape measures at right angles
2. Generate a pair of coordinates using a random number generator
3. Place a quadrat here and count frequency
   ○ Standardise this eg. only count it if it is more than half in the quadrat
4. Repeat a large number of times 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

Question 2

why is percentage cover used rather than frequency

Answer 2

too difficult too count individual organisms
as they may be too small to count

Question 3

importance of large sample size

Answer 3

minimise effect of anomolies
ensures sample size represents population

Question 4

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

Answer 4

● Calculate a running mean
● When enough quadrats, this shows little change
● Enough to carry out a statistical test

Question 5

Describe how you could investigate the effect of a factor on the distribution
of a species in a habitat (systematic sampling)

Answer 5

Place a transect line (tape measure) across an area with an environmental gradient e
2. Place quadrats at regular intervals eg. 1m (until end of transect) and record the number of organisms of
[named species] and [named environmental factor] eg. light intensity using a light meter
3. Repeat in other parallel areas and calculate mean number of plants at each point along the transect

Question 6

limitations of using systematic sampling to estimate population of a species in a field

Answer 6

not suitable unless envi gradient
transects run in one direction but to cover the entire field you’d need to place in multiple directions