The Structure and Characteristics of Fresh Water Ecology

The structure of the fresh water ecology refers to the nature and arrangement of the species and components of a typical fresh water ecosystem. Four main constituents of the living environment that form the fresh water ecosystem can be summarized as follows.

Elements and Compounds: These are some essential elements (such as carbon, oxygen, nitrogen, calcium and lead) and their compounds, which are absorbed by organisms in the ecosystem, and are required as a food source or for respiration. Many of these elements and their compounds are required by plants and are passed along the food chain.

The Primary Producers: These refers to plants which are autotrophic by nature In other words these plants are capable of synthesizing food by harnessing energy from inorganic compounds through the process of photosynthesis (plants do so by absorbing energy from the sun and using it the process of Primary Productivity).

These plants (and some bacteria) are therefore the primary producers, as they produce (and introduce) new energy into the ecosystem.

Consumers: These are the organisms that feed on other organisms as a source of food. These organisms depend on the primary producers for food supply, and may be primary consumers who feed from the plant material or secondary consumers who feed on the primary consumers.

Consumers who feed directly on the producers are mainly omnivores, while those who feed indirectly by feeding on the omnivores are known as the carnivores.

Decomposers: These are mainly micro-organisms which depend on the remains of the producers and consumers for survival. They therefore contribute to the energy transfer by breaking down dead organic material (detritus), and during this reaction, release critical elements and compounds which in turn are required by plants.

Plants, along with other organisms will inevitably die out, and the organic material produced by these dead plants decomposes into the soil, allowing new energy to be stored in the nutrient soil for plants to re-absorb.

This simple classification of life in the ecosystem indicates a simplified relationship where each passes on energy in the food chain allowing one another to survive.

The non-living component of the fresh water environment consists of the water and substance which provides an anchor to the living organisms.

There are always interactions of the living component not only within the organisms, but also with the non-living component.

Food Chains and Ecological Pyramids

An ecological pyramid indicates energy passing along from autotrophic organisms to carnivores at the top of the chain. Those at the bottom of the food chain are usually the smallest in size but not always, and are almost inevitably the largest in number.

Those who feed off these primary producers are less in number, usually because they are larger and require more than one portion of prey per meal as a means of fulfilling nutritional requirements for a larger organism.

This situation continues to the top of the chain, where few secondary consumers are eaten by an even smaller amount of tertiary consumers.

This is typical of a food chain in a freshwater community. Sometimes the pyramid diagram of a food chain can be inversed, usually in the case of parasites and hyper-parasites, where many smaller organisms rely on much larger organisms as a means of food and survival.

Just like in the case of other ecosystems where the simply food chain is merely illustrative, the same is the case of fresh water ecosystems.

The nature of energy transfer or feeding relationship is often very complex, and can best be described as a food web, where more than one organism are dependent on organisms of the lower trophic level for food supply.

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When energy is passed on, there is always a net loss in the energy that is available in the ecosystem. This is because some energy is always lost somewhere along the line due to inefficiencies and waste produced by each of the organisms that contains some of the biological energy that was created inside them.

Detrivores (decomposers) will feed on this waste matter, and once again the energy will be re-siphoned back into the food chain.

Trophic Levels

Food chains that allow a diversity of species to survive are divided into trophic levels, with plants providing the first trophic level as they are the primary producers of most food chains.

In almost all freshwater ecosystems, animals will be present, and form part of the many grazing food chains in the area.

Other organisms leach the energy from dead organic matter forming detritus food chains. Such relationships allow the free flow of organic energy to be passed along from species to species, and provide an environment where food is available for them to survive.

The most important fact to be taken from this is that no matter what species occupies an area; chances are they will require another species to be in abundance in the area for feeding.

The population of a particular species will depend on density dependent and density independent factors, therefore the abundance of food in the ecosystem (a density independent factor), comes into play.

The prey of a particular species will also require the existence of a food source for them to survive, and so forth.

Therefore we can see how the complex interrelationships between organisms allow an ecosystem to support such a wide variety of organisms.

Plants are the essential constituent for a healthy freshwater ecosystem, being the primary producers and harnessing energy from sunlight, they provide the building blocks and energy to allow the arrival of herbivores, and subsequently omnivores and carnivores into the ecosystem.

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