IB Environmental Systems and Societies/Measuring biotic components of the system
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2.3 Measuring biotic components of the system
2.3.1 Construct simple keys and use published keys for the identification of organisms.
- Dichotomous Keys
2.3.2 Describe and evaluate methods for estimating abundance of organisms.
2.3.3 Describe and evaluate methods for estimating the biomass of trophic levels in a community.
2.3.4 Define the term diversity.
- Diversity is often considered as a function of two components: the number of different species and the relative numbers of individuals of each species.
2.3.5 Apply Simpson’s diversity index and outline its significance.
- Formula: D = N(N − 1)/ ∑ n(n − 1)
Where:
- D = diversity index
- N = total number of organisms of all species found
- n = number of individuals of a particular species
- D is a measure of species richness. A high value of D suggests a stable and ancient site, and a low value of D could suggest pollution, recent colonization or agricultural management. The index is normally used in studies of vegetation but can also be applied to comparisons of animal(or even all species) diversity.