Required practical - measuring a population size
Measuring a population size
Greg Foot describes how to carry out a field investigation into distribution and abundance of organisms in an ecosystem
Aim
To measure the species richness on the school field in areas in which the grass is regularly and irregularly cut.
Method
- Choose a starting point on the school field in an area where the grass is often cut.
- Use randomOccurring without a pattern. Unpredictable. In statistics where each item has an equal probability of being selected. numbers to generate a set of coordinates to place your first quadratA square frame of known area used for sampling the abundance and distribution of slow or non-moving organisms..
- Count the number of different plant speciesA type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully. within this quadrat - this is described as the species richness.
- Return to your starting position and repeat steps two and three a further 14 times using different random numbers.
- Repeat steps one to four for a part of the school field which the grass is infrequently cut.
- Compare your results by calculating a meanThe total of the numbers divided by how many numbers there are. for each location.
Results
| Quadrat number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| Number of plant species per quadrat (on cut area of the school field) | 1 | 2 | 1 | 2 | 3 | 1 | 3 | 1 | 1 | 1 | 2 | 3 | 2 | 1 | 1 |
| Number of plant species per quadrat (on uncut area of the school field) | 3 | 2 | 4 | 6 | 1 | 1 | 1 | 4 | 5 | 3 | 6 | 4 | 5 | 3 | 4 |
| Quadrat number |
|---|
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
| 10 |
| 11 |
| 12 |
| 13 |
| 14 |
| 15 |
| Number of plant species per quadrat (on cut area of the school field) |
|---|
| 1 |
| 2 |
| 1 |
| 2 |
| 3 |
| 1 |
| 3 |
| 1 |
| 1 |
| 1 |
| 2 |
| 3 |
| 2 |
| 1 |
| 1 |
| Number of plant species per quadrat (on uncut area of the school field) |
|---|
| 3 |
| 2 |
| 4 |
| 6 |
| 1 |
| 1 |
| 1 |
| 4 |
| 5 |
| 3 |
| 6 |
| 4 |
| 5 |
| 3 |
| 4 |
Question
What are the totals and means for the two different locations?
A total of 25 and a mean of 1.7 on cut school field and a total of 52 and a mean of 3.5 on uncut school fields.
Conclusions
Question
What conclusions can you draw here? [4 marks]
The mean of the number of plant species in the cut school field is lower than on the uncut school field (1 mark). There is a mean of 1.7 different species per quadrat on the cut grass (1 mark). The number of plant species per quadrat on the uncut field is over twice this at 3.5 (1 mark). Therefore, there is greater species richness on the school field in uncut areas (1 mark).
Question
What limitations might there be in drawing these conclusions?
The two students only placed 15 quadrats. Completing more would allow them to be more confident in their conclusions.
