The Concept of the Ecosystem

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The Concept of the Ecosystem

An ecosystem includes all the living organisms that interact with one another and also with the physical and non-physical factors present.

The boundaries of the ecosystem studied are dictated by the individual carrying out the study. It may be as large as the biosphere or as small as an enclosed bacterial colony.

The following are important terms which are frequently used in ecology...

Habitat: The place where an organism lives.

Population: A group of organisms, all of the same species, and all of whom live together in a particular habitat.

Community: The total of all populations living together in a particular habitat.

Niche: The position occupied by an organism in a particular ecosystem, dependent upon the resources it uses. The more resources that are taken into account then the more carefully defined the organism's niche will be, the organism will become more specialised.


Ecosystem: The biotic community together with the abiotic environment.

In order to study an ecosystem it is essential that the way in which organisms interact with each other within the ecosystem is considered. These relationships are the biotic factors of the ecosystem.

It is also essential that the effects of the physical or non-living factors are considered. These are the abiotic factors.

Biotic factors:

The biotic factors affecting an ecosystem are mainly concerned with competition either within a single population or between the members of different populations.

Abiotic factors:

These are the physical factors that affect an ecosystem. They include the following:

Light: Many plants are directly affected by light availability since light is required for successful photosynthesis. Plants develop strategies in order to cope with different amounts of available light.

They may have larger leaves; develop photosynthetic pigments that require less light; reproduce when light availability is at an optimum.

Temperature: The major effect of temperature is on the enzymes controlling metabolic reactions. As a rule plants will develop more rapidly in warmer temperatures, as will ectothermic animals. It is partly due to temperature that migrations occur.

Water availability: This is mainly a problem in terrestrial ecosystems and does not affect aquatic ecosystems.

In most populations a lack of water leads to water stress which, if severe will lead to death. There are some organisms (e.g, cacti and camels), which have developed successful strategies to cope with water stress.

Niche Niche

Oxygen availability: This may be a limiting factor in soil or water. In aquatic ecosystems it is better to have fast flowing cold water as it holds a higher concentration of oxygen.

If water becomes too warm, or the flow rate is too slow there may be a drop in oxygen concentration leading to suffocation for many aquatic organisms.

A similar situation occurs in waterlogged soil where the air spaces between the soil particles are filled with water, reducing the available oxygen for any plants.

Edaphic factors: This term covers any factors referring to soil. There are three main soil types, clay, loam and sand. The different soil types have different particle sizes, this will have an effect on the organisms that are able to survive in them.

Clay soil has fine particles, is easily waterlogged and forms clumps when wet.

Loam soil has particles of different sizes, retains water and does not become waterlogged.

Sandy soil has coarse, well separated particles which allow free draining. They do not retain water well and are easily eroded by wind and water.

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