Biotic Factor: A living variable within the ecosystem, which affects the survival of organisms. Examples include predation, competition, and pollution from excreted waste.
Abiotic Factor: A non-living variable within the ecosystem, which affects the survival of organisms. Examples include temperature, light, and water.
Random Sampling (quadrats placed at randomly generated intervals)
- Used where habitat is uniform
- Removes observer bias
- Used in a large area
- Used if time is limited
Systematic Sampling (quadrats placed at regular intervals)
- Used to show zonation
- Used where there is continuous variation
- Used to sample linear habitats (e.g. a roadside)
2 types of systematic sampling technique;
Line Transect:
- Used where time is limited
- Used to visually illustrate how species change along a line
Belt Transect:
- Produces more data, gives detail about species abundance down the line as well as range
- Shows species dominance down the line
What interval should be used?
Transects can either be continuous with the whole length of the line being sampled, or samples can be taken at particular points along the line
For both line and belt transects, the interval at which samples are taken will depend on the individual habitat, as well as on the time and effort which can be allocated to the survey.
- Too great an interval may mean that many species actually present are not noted, as well as obscuring zonation patterns for lack of observations.
- Too small an interval can make the sampling time consuming, as well as yielding more data than is needed.