Ecosystem Organization

When studying ecology and all the interacting relationships that occur within the environment, there are different levels of interactions one can look at depending on what it is they wish to study - community ecology and population ecology are two subdisciplines that each study specific types of interactions. Like how the human body has levels of sub-organization that you may be familiar with (cells, tissues, organs, and organ systems), so too does an ecosystem.

As we go through the organization of an ecosystem, we will do so using Acadia National Park in Maine as our illustrative example.

The lowest level of organization in an ecosystem is at the level of the individual - a single organism. This is an individual living thing of a particular species. In our example, it is a single moose - let's call him Bullwinkle.

A group of organisms of that species that live in a certain area is known as a population. The population would be Bullwinkle and all the other moose in Acadia.

In that same particular area, there are multiple populations of various species. This is known as a community. The community consists of all of the living (or biotic) things in that region. Our Acadia community would be the populations of moose, deer, coyotes, rodents, hares, beavers, fishers, birds, pines, spruces, firs, mushrooms, bacteria, and all other populations in the park.

An environment is not made up only of living things, however. An ecosystem consists of the community and the nonliving (or abiotic) factors in their physical environment with which they interact. This would include not only all the animals, plants, microbes, etc., but also the water, air, rocks, climate, soil, and other nonliving aspects of the environment.

Earth has numerous unique and interesting ecosystems with an immense variety of species within different communities. However, you can imagine that ecosystems with more similar abiotic factors may tend to be similar to each other in their community compositions. Biomes are large regions with similar and characterizable ecosystems, characterized by their climate (particularly temperature and precipitation) and their dominant plant species.

Up until now, the characteristics that have been discussed apply to differentiating between the different environments found on land, as that is what is traditionally referred to when one is discussing a biome. However, there are communities that do not live on land; some ecosystems exist entirely within the water. Earth's biomes can be split into two major categories: terrestrial biomes and aquatic biomes. Aquatic biomes have slightly different characteristics that differentiate them from those already mentioned for terrestrial biomes. The major characteristics of aquatic biomes are salinity (amount of salt in the water), temperature, turbidity (cloudiness), depth, dissolved oxygen content, water flow, and nutrient availability. The producers in aquatic biomes have specially adapted characteristics due to a lack of visible light; most red light is absorbed in the first 1m of water and most blue light is absorbed within 100m in even the clearest water.