Explain why scientists use random sampling when investigating the biodiversity of a habitat.

AQA A-Level Biology (7402) — 3.4.7 Investigating Diversity · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A group of students wants to estimate the number of different species of plants in a meadow. They decide to use quadrats to collect data.

Model answer (5 marks)

Scientists use random sampling to avoid bias in the placement of quadrats, ensuring that each area of the habitat has an equal chance of being selected.

This method makes the data representative of the whole habitat or population, rather than just a particular area.

A larger sample size, obtained through random placement, reduces the influence of chance or anomalous results, giving more reliable estimates.

The unbiased, representative data can then be used to estimate overall species diversity or the total number of species in the habitat.

Random sampling can be achieved by using a random number generator or random coordinates to place the quadrats, guaranteeing that the selection process is truly random.

Examiner tips

  • Use the exact phrase ‘avoid bias’ and ‘representative of the whole habitat’. Mention that a larger sample size reduces chance effects. Explain how random placement allows estimation of overall diversity. Show how random numbers or coordinates are used to place quadrats.

Common mistakes

  • Assuming that systematic sampling is the same as random sampling. Failing to mention that random sampling reduces bias. Not explaining how random placement leads to estimates of overall diversity.

Mark scheme (5 marks)

  1. Random sampling avoids bias (in the placement of quadrats)
  2. So that results are representative of the whole habitat / population
  3. A larger sample size reduces the effect of chance / anomalous results
  4. Results can be used to estimate species diversity / number of species across the whole habitat
  5. Random sampling can be achieved by using a random number generator / coordinates to place quadrats

Key terms in this question

random sampling · biodiversity

Related

More Investigating Diversity questions

▶ Try answering this question with AI marking (free) →