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A community is a set of different species that live in the same area and interact with each other. These organisms form a complex web of relationships within the ecosystem they are a part of. Each community and their ecosystem is influenced by these interactions as well as by external forces such as disruptions to the environment.
Community Structure
The structure of a community is described by its species composition and species diversity. Species composition is a term used to describe the specific species that make up a community. Species diversity describes the number of species and the relative abundance of these species in an ecosystem. This is an important aspect in understanding community structure because it shows how individuals in a community are distributed among those species. For instance, species composition might show that there are wolves, elk, deer, and ground squirrels living in a community. However, species diversity would add a layer and show that there is only one wolf, 300 elk, and 500 deer. This changes our view on whether it is a balanced community or not.
Simpson’s Diversity Index is a way of quantifying this diversity. It provides the probability that two randomly selected individuals will belong to the same species. This allows one to assess which species are dominant in a community. The higher the value of D, the lower the diversity since it indicates that only a few species dominate the community.
The equation for Simpson’s Diversity Index is:
\(D = 1-∑(n/N)^2 \)
Where:
n = total number of organisms of a particular species
N = total number of organisms of all species
Biomes
A biome is a geographic area that has specific characteristics and qualities. Biomes are created by unique climate zones but contain vegetation and animal communities that are adapted to these environments. Some examples of biomes include deserts, grasslands, tundra, and tropical rainforests. While biomes can exist in multiple places across the globe, they will share similarities with each other. Biomes differ from ecosystems in that they are a broader category while ecosystems are more localized communities of organisms.
