A student wanted to investigate the biotic factors influencing the activity of leaf-litter invertebrates on a woodland floor. She focused her study on a species of woodlouse found under decomposing logs and leaf litter in dark, damp microclimates.
She used pitfall traps to sample active organisms in a section of the woodland, setting one set of traps during the day and another identical set during the night, counting the organisms captured before releasing them.
From the day-time sample, she produced the following table of results:
| Organism | Tally | Number |
|---|---|---|
| Woodlice | ∥∥∥∥\cancel{\|\|\|\|}∥∥∥∥ | 5 |
| Centipedes | ∥∥\|\|∥∥ | 2 |
| Rove Beetles | ∥∥∥∥ ∥∥∥∥\cancel{\|\|\|\|}\ \cancel{\|\|\|\|}∥∥∥∥ ∥∥∥∥ | 10 |
| Millipedes | ∥∥∥\|\|\|∥∥∥ | 3 |
Below is the night-time sample collected from the traps:
Complete the table below for the night-time sample by writing down the Tally and Number for each organism.
| Organism | Tally | Number |
|---|---|---|
| Woodlice | ? | ? |
| Centipedes | ? | ? |
| Rove Beetles | ? | ? |
| Millipedes | ? | ? |
Compare the total number of organisms, as well as the number of woodlice, collected during the day-time and during the night-time.
Suggest two explanations for the difference in the number of woodlice collected at night compared to the day.
The organisms caught in the trap remained there for up to 12 hours before being counted. Suggest how this might affect the validity of the results.
With reference to this investigation, define the following terms: (i) population (ii) community (iii) habitat