(A Level) Biodiversity, sampling and statistics

Learning objectives

Define ecosystem and niche, and explain the three levels at which biodiversity is assessed: variety of ecosystems and habitats, species richness and relative abundance, and genetic diversity within species.

Explain how random sampling, for example using random-number coordinates on a grid, avoids bias when estimating the biodiversity of an area.

Describe and use frame quadrats, line transects and belt transects to measure the distribution and abundance of organisms, and estimate population size by mark–release–recapture with the Lincoln index.

Calculate and interpret Spearman's rank and Pearson's linear correlation coefficients to test whether two variables, such as a biotic or abiotic factor and the abundance of a species, are related, judging significance against critical values.

Calculate Simpson's index of diversity, D = 1 − Σ(n/N)², and explain what high and low values of D show about a community.