What is an ecosystem?
An ecosystem is the living and non-living components of an environment and the interrelationships that exist between them.
In any ecosystem, the living things interact with the environment and each other. For example, caterpillars in a wood breathe the air, feed on leaves, and get eaten by birds. If it
gets too cold, they die.
Non-living components include the climate (temperature and rainfall), soil, water and light.
Ecosystems can exist at different scales – a pond to tree to a hedgerow to the tropical rainforest or even the whole Earth.
How do ecosystems work?
We will use a small scale ecosystem such as a wood in the UK.
All ecosystems work in the same way. Animals: A woodland ecosystem provides a habitat for a huge range of animals, such as squirrels, rabbits and deer – as well as insects and birds
Plants: Vegetation grows in layers – with taller trees smaller trees and shrubs a herb layer of early flowering plants (such as bluebells) and a ground layer.
Soil: The most common type of soil is brown earth
Climate: Summers are warm, winters are cool
Every ecosystem works in the same way; whether a small woodland to a large tropical rainforest
The plants use sunlight, water and nutrient from the soil to produce their own food (so they’re called Producers)
The animals feed on the plants, or each other (so they’re called consumers)
Fungi and bacteria feed on dead and waste materials, and make things break down or rot (so they’re called decomposers) – they recycle nutrients for the plants to use again.
Without plants all other things would die.
Food webs and food chains
In any ecosystem, animals need to eat to survive – and whatever is eaten is part of the food chain. In the oak woodland, it works like this:
oak leaf ————> caterpillar —————> wood mouse ————–> fox
(The arrow means: ‘it gets eaten by’ and shows a flow of energy in the ecosystem)
Often several consumers eat the same type of food. So, for example, caterpillars and aphids (a type of fly) both feed on oak leaves.
Individual food chains then link up to form a food web.
Nutrients continually circulate within ecosystems as the diagram to the left shows:
Ecosystems work because there’s a flow of energy through them. The main source of energy is sunlight, which is absorbed by plans and then
converted by photosynthesis. Energy passes through the ecosystem in the food chain. Each link in the chain feeds on – and gets its energy from – the link before it
Non-living environment ————-> Producers ————————> Consumers ——————> Consumers——————————-> Decomposers
Sunlight is the main source of energy which Green plants convert by photosynthesis
Herbivores eat plants and obtain their energy from them
Carnivores eat herbivores,
Omnivores eat both
Changes to ecosystems
Different parts of an ecosystem depend on each other, and there’s a balance between them. A change in
one part of an ecosystem will affect other parts and upset the balance.
Ecosystems around the world are facing changes, or threats, including:
Climate change – which can affect where species can live, when the reproduce, and the size of their population
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 algal growth (called algal blooms)