BRAINCAKESpecies Abundance
Abundance is the number of individuals of a species in a given area. Ecologists measure abundance to compare habitats, monitor changes over time and assess the effect of human activity.
It is rarely possible to count every individual, so abundance is estimated from samples, which must be taken at random to avoid bias. Common measures include:
- Population density: number of individuals per unit area, e.g. per m2. Best for organisms that are easy to count separately.
- Frequency: the percentage of sampling squares (quadrats) in which the species occurs. Quick, but does not tell you how many there are.
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Key terms in this lesson
- mark-release-recapture
- A method of estimating the size of a mobile animal population by capturing, marking, releasing and recapturing a sample.
More in The Nature of Ecosystems
- Density Independent Factors
- Competition
- Intraspecific Competition
- Interspecific Competition
- Species Distribution
- Ecological Techniques
- Quadrats
- ACFOR Scale
All 39 lessons in The Nature of Ecosystems · All Edexcel A-level Biology topics