Community Ecology Overview

• Community ecology is the study of the interactions among a collection of species that inhabit the same geographical area.
• These organisms interact with one another within a community. This includes different species of plants, animals, bacteria, and fungi.
• The community is determined by the local climate, soil, and other environmental factors, and it significantly affects the abundance and distribution of species.

Community Interactions

• Mutualism is a type of interaction where both species benefit. An example is bees pollinating flowers while collecting nectar for food.
• Predation and herbivory are interactions where one species benefits at the expense of another. Predation involves a predator (a carnivore) eating a prey (typically a herbivore), whilst herbivory involves a herbivore eating a plant.
• Competition occurs when two or more species rely on the same limited resource. This can result in competitive exclusion, where one species outcompetes the others for resources.

Community Structure and Dynamics

• A community’s structure includes the number, type, and abundance of species present.
• The biodiversity within a community can be described in terms of species richness (the number of different species) and species evenness (the relative abundance of different species).
• Communities are not static; they change over time due to disturbances, which can be caused by natural phenomena (e.g., storms, fires) or human activities (e.g., logging, pollution).
• Over time, ecological succession occurs, where species compositions change gradually. This could be primary succession, where species inhabit a previously uninhabited area, or secondary succession, where species recolonize an area after disturbances.

Food Webs and Energy Flow

• Energy in an ecological community flows through food chains, which are linear representations of who consumes whom in a community.
• Food webs are more complex, showing multiple interconnected food chains.
• Each level of a food chain or web is called a trophic level. Energy decreases at each subsequent trophic level, explained by the 10% rule where only about 10% of energy is transferred from one trophic level to the next.
• Decomposers like bacteria and fungi are essential in the community as they break down dead organisms and waste, returning nutrients back to the environment.

Community Stability and Resilience

• Community stability refers to the ability of a community to maintain a particular state, despite disturbances.
• Resilience, on the other hand, is the ability to recover quickly to a stable state after a disturbance.
• Greater biodiversity often leads to increased stability and resilience, as a diverse community is better equipped to withstand stresses and less likely to be drastically altered by disturbances.