LW+-+What+is+an+ecosystem


 * __What is an ecosystem?__**

An ecosystem is the living and non-living components of an environment and the interelationships 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 aire, 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.

The photo below shows a small oak woodland ecosystem in the UK: Animals: A woodland ecosystem provdes a habitiat for a huge range of animals, such as squrriels, rabbits and deer - as well as insects and birds

Plants: Vegetation grows in layers - with taller treesm smaller trees and shrubsm 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 nutirent 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 chains and food webs__**

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 severl 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. The diagram below shows a food web The link below is an interactive foid web giving you more detail on the animals and plants who live there: []


 * __Ecosystem processes__**

Ecosystems depend on two basic processes - recycling nutrients and energy flows.


 * Recycling nutrients**

Nutrients continually circulate within ecosystems as the diagram below shows:


 * Energy flows**

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 cnverted 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 Green plants convert Hebivores eat Carnivores eat herbivores, Bacteria and fungi source of energy energy by photosynthesis green plants 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. Ecocsystems 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 habitiat 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)

__**Key terms:**__

Ecosystem: the living and non-living components of an environment and the interrelationships that exist between them Biomes: gloabl-scale ecosystems Adaptations: the ways that plants evolve to cope with certain environmental conditions such as excessive rainfall Producers: organisms that obtain their energy from a primary source such as the sun Consumer: organisms that obtain their energy by eating other organisms Food chain: a line of linkages between producrs and consumers Fod web: a diagram that shows all the linkages between producers and consumers in an ecosystem Scavengers: organisms that consume dead animals or plants Decomposers: organisms such as bacteria that break down plant and animal material Nutrient cycling: the recycling of nutrients between living organisms and the environment