Field guide training: Ecology – Part 2

An ecosystem is a dynamic complex of communities of plants, animals and microorganisms and their non-living environment that interact as a functional unit. They are subject to constant physical parameters and environmental influences. Most ecosystems today experience the greatest external influence from humans.

The main pressures on the environment and thus on most ecosystems are the increasing urbanisation of rural areas, the promotion of natural resources, pollution and climate change. This leads to changes in their physical and biological composition, but not all ecosystems react sensitively. Stable or resistant ecosystems show a change only after a long period of harmful exposure, others are very susceptible to disruption. This depends above all on how tolerant the biocoenoses of an ecosystem are or how many species losses they can cope with without decaying. As a field guide, you should have a sound knowledge of ecosystem development in order to understand how to adequately protect them.

Functional components

• Productivity and energy flow
• Nutrient and chemical cycle
• Limiting factors

Structural components

• The structural components of an ecosystem consist of its biotic and abiotic factors.

Abiotic factors

• Climate (precipitation, temperature, humidity, solar radiation, etc.)
• Soil (soil composition, nutrients, water content)
• Physiography (topography, extension, height)
• Fire (an important additional aspect in some ecosystems)

Biotic factors

The biotic or living factors of an ecosystem are mainly formed by the organisms living in it. Animals, plants and microorganisms are often divided into producers, consumers and decomposers. Producers are organisms such as algae, green plants and cyanobacteria that are able to produce their own food through photosynthesis. They are therefore also called autotrophic ("self-nourishing"). Solar energy, carbon dioxide and water are used to produce glucose or starch. These carbohydrates serve the planters themselves as well as the animals that eat them as food or chemical energy source.

Organisms that are unable to produce their own food and therefore depend on other organisms are called consumers. Primary consumers such as the kudu feed mainly on plant material. Secondary consumers like the lion eat the same animals that only eat plants. The group of tertiary consumers also includes carnivorous species in their range of prey. Hyaenas are a classic example of a tertiary consumer.

Decomposers play a particularly important role in the nutrient cycle, as they can decompose any form of organic material, including animal carcasses, dead wood or other dead plant material. They convert the organic substances into inorganic substances and thus feed them into the nutrient cycle, where they are again available to the producers. Decomposers have different strategies to absorb their food, i.e. organic residual substance: Many bacteria absorb their food through their cell membrane. Other organisms such as so-called saprophytic fungi digest them outside the body and then absorb them in an easily accessible form. Termites, which are also destructors, have mechanical and chemical tools to break down the organic matter they feed on.

As a field guide, it is important to know these relationships as they contribute to a basic understanding of energy flows and food relationships in nature.