Understanding:
• Richness and evenness are components of biodiversity
Biodiversity describes the variety and variability of all living organisms within a given ecological area
- Biodiversity can be used to refer to the number of species, their genetic diversity or habitat variety (ecological variations)
There are two main components that contribute to biodiversity – species richness and species evenness
- Species richness describes the number of different species present in an area (more species = greater richness)
- Species evenness describes the relative abundance of the different species in an area (similar abundance = more evenness)
Biodiversity (Richness versus Evenness)
Skill:
• Analysis of the biodiversity of two local communities using Simpson’s reciprocal index of diversity
The Simpson’s reciprocal index can be used to measure the relative biodiversity of a given community
- It takes into account both the number of species present (richness) and the number of individuals per species (evenness)
- A higher index value is indicative of a greater degree of biodiversity within the community
Simpson’s reciprocal index can be used to compare communities to identify intrinsic qualities:
- A high index value suggests a stable site with many different niches and low competition (high richness and evenness)
- A low index value suggests a site with few potential niches where only a few species dominate (low richness and evenness)
- The index value may change in response to an ecological disturbance (such as human intervention or natural disasters)
Practice Question
