B7 - Ecosystems

Closed loop systems.

• All outputs are recycled within a closed loop system
• Theres no waste from a perfect closed loop system
• Theres no inputs added in a perfect closed loop system
• However, most systems arent perfect closed loops - they have inputs to them and outputs from the

Ecosystems are a type of closed loop system because most of the waste (output) produced by organisms isnt lost - its recycled as food or reactants for other microorganisms in the system. 

• For e.g. oxygen is a waste product produced by plants during photosynthesis. Its used by plants, animals and microorganisms as a reactant during respiration
• Carbon dioxide is a waste product produced by repiration. Its used by plants as a reactant during photosynthesis. 
• Dead organic matter is used by microorganisms as food

Humans cause a lot of damage to ecosystems by changing inputs and outputs, for e.g.

• Farmers use fertillisers to give plants extra nutrients to help them grow. But this unbalances ecosystems because the input of nutirents is muvh higher than normal. It can lead to eutrophication. 
• Humans take biomass out of ecosystems for their own use - this can damage an ecosystem.

    > Over fishing removes a food source for some of the organisms in a food chain

    > Unsustainable timber harvesting removes habitats and food sources for some organisms

• Humans often clear natural areas of vegetation in ecosystems so they can grow agricultural crops and raise livestock. 
• Human Activites create non-recycable waste that cant be used again within a system. This can build up to harmful levels in the ecosystem

Human systems arent closed loop systems. This is because human systems create non-recycable waste and many human systems use fossil fuels such as crude oil, as an energy source.

Using fossil fuels means that human sytems arent closed loops. Heres why

• It produces waste emissions that arent used again in the system
• Fossil fuels take millions od years to frm from decay of dead organisms, but only seconds to usee. Because they take so long to form, they cant be made again within the system.