school energy&environment

The ecosystem: a complex system

An ecosystem is a complex system composed of organisms living in a given habitat. Plants and animals are the biotic components of the ecosystem, while the subsoil, water, air, light, temperature, the climate, rains are part of the abiotic components. In an ecosystem, the biotic components that inhabit it and the abiotic ones establish a set of relationships with each other that characterise the ecosystem itself and bring it to a temporarily “balanced” state.
According to their task within an ecosystem, the biotic components (living organisms) can be divided into:

• producers (plants, algae and some bacteria): these are “autotrophic” organisms that produce by themselves the organic matter they need to live and grow, using such simple inorganic molecules as water, carbon dioxide (CO₂) and nitrates
• consumers are defined as “hetero-trophic” organisms, since they cannot produce their own nourishment, but feed on producers (for instance, the herbivore consumers, such as cows and sheep, that eat grass) or on other consumers (carnivore consumers, such as lions or man)
• decomposers are fungi and bacteria that feed themselves by decomposing the tissues of dead organisms.

Each ecosystem contains a given amount of organic matter that includes all its vegetal and animal organisms: the weight of such matter is called ‘biomass’, and is calculated dry and per surface unit occupied by the ecosystem.