Title
Sampling
Ecological Sampling
Ecological sampling is the process by which small representative sections of an area are used to estimate the composition or properties of a larger area. The representative sections are called samples.
One type of sample is the food samples that are sometimes passed out at grocery stores. A store may be trying to convince customers to buy a certain product, like a brand of pizza, by offering bite-sized samples (e.g. Fig. 1). Customers only get to taste the sample, so they have to assume the whole pizza will taste like the sample. However, if the pizza has many different toppings, the sample piece may not have all of the toppings on the pizza. For example, a customer who receives the pizza sample in Fig. 1A would assume that it is a pepperoni pizza. Another sample (Fig. 1B) would reveal that the pizza has mushrooms and peppers. Samples C and D would provide even more information. By sampling the pizza many times, a customer is more likely to taste a variety of toppings and be able to more accurately describe the entire pizza.
[Insert Fig. 1]
The need to analyze multiple samples before making conclusions is important not only in shopping for pizza, but also in scientific sampling. In order for estimates to be accurate, samples should be representative of the whole–the whole pizza, the whole population, or the whole area. However, there is no guarantee that any sample will be perfectly representative of the whole. Thus, replication, or repeated sampling, is important.
Sampling is a powerful tool that is important across many scientific disciplines. The type of sample will depend on the discipline and on the task involved (see Table 1).
Table 1. Examples of sampling across scientific disciplines
| Discipline | Study Purpose | Specific Task | Sample Characteristics |
| Medicine | Determine the overall health of a dog using blood cell types as an indicator | Determine the percentage of each type of blood cell in a dog | Blood draws using sterile needles |
| Geology | Determine historical atmospheric carbon dioxide composition using ice layers | Determine the various composition of layers of ice in a large ice sheet | Cores drilled into an ice sheet |
| Chemistry | Investigate mercury levels in various aquatic environments over time | Determine levels of mercury in a freshwater lake | Water samples collected at different locations and depths in the lake |
| Population Ecology | Look at change in snail population over time to assess changes in population | Determine number of snails on a rocky beach | Count snails in a number of small areas on the beach |
| Genetics | Determine if two fish populations that look similar are connected or if they are distinct populations | Use genetic analysis to determine if there is a genetic difference between two populations of fish | DNA extracted from fish from each location |
