Exercises: Ecological Fieldwork and Data Handling

Name the sampling instrument you would use to estimate each of the following on a rocky shore: (i) the percentage cover of seaweed, (ii) the distribution of a species along a transect from high to low tide, (iii) the number of small mobile animals in a rock pool. Describe one measure to make sampling unbiased.

Name one instrument used to measure each of these abiotic factors in a habitat: light intensity, temperature, soil pH and soil moisture. State one precaution to ensure the reading is reliable.

Distinguish between accuracy and precision, and between random error and systematic error, with one example of each.

A student places a 0.5 m × 0.5 m quadrat 10 times in a field of area 2,000 m² and counts the number of dandelions in each quadrat: 3, 5, 2, 4, 6, 3, 5, 4, 2, 6.

1. a) Calculate the mean number per quadrat.

1. b) Calculate the mean density per m².

1. c) Estimate the total population in the field.

1. d) Suggest how the student could improve the reliability of the estimate.

A mark–recapture study of woodlice in a garden in Limerick: 40 woodlice were captured, marked and released. A second sample of 50 contained 10 marked.

1. a) Calculate the estimated population using $N = \frac{M \times C}{R}$.

1. b) State three assumptions of this method.

1. c) Explain how one assumption could be violated and the effect on the estimate.

Soil pH was measured at five points along a transect from a hedgerow into a field: 6.8, 6.5, 6.1, 5.9, 5.7.

1. a) Describe a suitable graph and how to label it.

1. b) Calculate the mean and the range.

1. c) Describe the trend and suggest an ecological explanation.

A class investigates whether light intensity affects the density of a moss species on a woodland floor. They record data at 12 points.

1. a) State a hypothesis and a null hypothesis.

1. b) Identify the independent, dependent and two controlled variables.

1. c) Explain why a correlation does not prove that light causes the variation in moss density.

1. d) Suggest two improvements and explain how each would reduce error.

A student reports that mean beetle number per pitfall trap is 8.2 ± 1.1 (SD, n = 10) in woodland and 5.9 ± 3.4 (SD, n = 10) in grassland, and concludes that woodland has "definitely" more beetles.

1. a) Explain what the standard deviation shows about each data set.

1. b) Evaluate the conclusion.

1. c) Suggest what further data or statistical test would strengthen it.

1. d) Identify two ethical or conservation considerations for pitfall trapping.

An online article claims "a new study proves that a herbal supplement boosts immunity" based on 12 volunteers with no control group, funded by the supplement's manufacturer.

1. a) Identify four weaknesses in the study design or the source.

1. b) Explain what a well-designed investigation would include, with reference to control, sample size, blinding and replication.

1. c) Explain how you would assess the reliability of a scientific source in a media report, and what features separate a peer-reviewed paper from a press release.