AQA GCSE Biology

Sampling & quadrats

AQA GCSE Biology revision on Sampling & quadrats. Aligned to the AQA GCSE Biology 8461 specification. This bank has 25 practice questions on this topic.

Sample questions (3 of 25)

  1. Question 1

    Why is it essential to place quadrats randomly within a survey area?

    • A) To ensure a large sample
    • B) To avoid sampling bias
    • C) To locate rare species
    • D) To map exact locations
    Show answer

    Answer: To avoid sampling bias

    If a researcher chooses where to place quadrats, they may unconsciously select areas with more organisms, leading to an overestimate. Random sampling ensures that every part of the habitat has an equal chance of being surveyed, providing a representative estimate of the total population.

  2. Question 2

    What is the primary purpose of using a transect line when investigating the distribution of plants?

    • A) To measure species density
    • B) To show change over distance
    • C) To count total population
    • D) To identify new species
    Show answer

    Answer: To show change over distance

    Transects allow biologists to systematically record changes in species composition or abundance along a line, such as moving from a sunny area to a shady area. Unlike random quadrats, which give a total estimate, transects reveal patterns related to changing environmental factors like light or soil pH.

  3. Question 3

    Which statistical measure should be calculated to provide the most reliable estimate of population size from multiple quadrat samples?

    • A) The sample median value
    • B) The sample range value
    • C) The sample mean value
    • D) The sample mode value
    Show answer

    Answer: The sample mean value

    A single quadrat may contain an unusually high or low number of organisms. By taking the mean of many samples, the researcher accounts for this variation and obtains a more accurate representation of the population density across the entire habitat.

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