An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. There are many examples of ecosystems -- a pond, a forest, an estuary, a grassland. The boundaries are not fixed in any objective way, although sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for practical reasons having to do with the goals of the particular study.
Each organism and population has a HABITAT - the place or type of place where an organism or population naturally lives within a community.
Ecological niche - role or work performed by an organism.
The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components. Energy transformations and biogeochemical cycling are the main processes that comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur. We can study ecology at the level of the individual, the population, the community, and the ecosystem.
Studies of individuals are concerned mostly about physiology, reproduction, development of behavior, and studies of populations usually focus on the habitat and resources needs of individual species, their group behaviors, population growth, and what limits their abundnance or causes extinction. Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.
In ecosystem ecology we put all of this together and, insofar as we can, we try to understand how the system operates as a whole. This means that, rather than worrying mainly about particular species, we try to focus on major functional aspects of the system. These functional aspects include such things as the amount of energy that is produced by photosynthesis, how energy or materials flow along the many steps in a food chain, or what controls the rate of decomposition of materials or the rate at which nutrients are recycled in the system.
Components of an Ecosystem
You are already familiar with the parts of an ecosystem. You have learned about climate and soils from past lectures. From this course and from general knowledge, you have a basic understanding of the diversity of plants and animals, and how plants and animals and microbes obtain water, nutrients, and food. We can clarify the parts of an ecosystem by listing them under the headings "abiotic" and "biotic". | | |
| Sunlight | Primary producers |
| Temperature | Herbivores |
| Precipitation | Carnivores |
| Water or moisture | Omnivores |
| Soil or water chemistry (e.g., P, NH4+) | Detritivores |
| etc. | etc. |
| | |
By and large, this set of environmental factors is important almost everywhere, in all ecosystems.
Usually, biological communities include the "functional groupings" shown above. A functional group is a biological category composed of organisms that perform mostly the same kind of function in the system; for example, all the photosynthetic plants or primary producers form a functional group. Membership in the functional group does not depend very much on who the actual players (species) happen to be, only on what function they perform in the ecosystem.
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