What is an ecosystem?

BBC Bitesize – biomes

An ecosystem is a set of biotic (living) and abiotic (non-living) elements and the links inbetween them. Each element in the system depends upon and influences others. They are interrelated. There are often complex relationships between the living (biotic) and non-living (abiotic) components. Abiotic components include the climate (primarily temperature and rainfall), soil, water and light. Biotic (living elements) are the flora (plants) and fauna (animals).

Ecosystems can be identified at different scales. A local ecosystem can be a pond or a hedge. Larger ecosystems can be lakes or woodlands. It is also possible to identify ecosystems on a global scale, such as tropical rainforests or deciduous woodland. These global ecosystems are called biomes.

How do ecosystems work?

Every ecosystem works in the same way:

  • Plants use sunlight, water and nutrients from the soil to produce their own food via photosynthesis and are called producers.
  • Animals feed on plants (herbivores) or animals (carnivores) and are called consumers.
  • Fungi and bacteria feed on dead and waste material and make things break down or rot. These are called decomposers and recycle nutrients for plants to use again.
  • Without plants, all other living things would die.

A food chain shows the different elements that live in an ecosystem, and what eats what to survive. A food web is more complex and shows all the different elements in a habitat and how they interrelate.

The nutrient cycle shows how nutrients continually circulate within ecosystems.

Changes to the ecosystem

Different parts of an ecosystem depend on each other, and there’s a fine balance between them. A change in one part of the ecosystem will affect other parts and upset the balance. Ecosystems around the world are facing changes including:

  • climate change – which can affect where species can live, when they reproduce and the size of their populations
  • habitat change – the conversion of land for farming can lead to a loss of habitat for huge numbers of species
  • pollution – which, for example, can reduce oxygen levels in wetlands and rivers (killing fish), and also cause rapid plant and algae growth (called algae blooms)