rp 12 Flashcards
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)
- Divide two areas into squares eg. place 2 tape measures at right angles
- Generate a pair of coordinates using a random number generator
- Place a quadrat here and count frequency
○ Standardise this eg. only count it if it is more than half in the quadrat - Repeat a large number of times and calculate a mean per quadrat for both areas
- Measure environmental factor in each area eg. take soil moisture readings with a soil moisture meter
why is percentage cover used rather than frequency
too difficult too count individual organisms
as they may be too small to count
importance of large sample size
minimise effect of anomolies
ensures sample size represents population
Describe how you could decide the number of
quadrats that should be used in order to collect
representative data.
● Calculate a running mean
● When enough quadrats, this shows little change
● Enough to carry out a statistical test
Describe how you could investigate the effect of a factor on the distribution
of a species in a habitat (systematic sampling)
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
limitations of using systematic sampling to estimate population of a species in a field
not suitable unless envi gradient
transects run in one direction but to cover the entire field you’d need to place in multiple directions