Ecosystems

Biotic

• Living components such as plants and animals

Abiotic

• Non-living components such as climate, soil, relief, drainage and altitude

• Ecosystem is an open system

Inputs:

• Nutrients from weathered rock
• Precipitation
• Solar energy (insolation)
• Gases from atmosphere

Stores:

• Animals
• Plants
• Soil

Transfers:

• Involve energy and materials in the form of nutrients

Outputs:

• Nutrients from leached soil
• Gases (CO2)
• Water
• Energy as heat

• Energy moves through a series of trophic levels and leaves via heat
• Sun is primary source of energy
• Light energy is used by autotrophs in photosynthesis which creates chemical food energy
• This energy fixed by photosynthesis becomes available to subsequent trophic levels forming a food chain
• First Trophic Level: plants that produce their own food directly- autotrophs or producers
• All other levels consume plants and other organisms in previous level- consumers or heterotrophs
• Second Trophic Level: herbivores consume plants from first level and in turn provide food for Third Trophic Level: smaller carnivores
• Fourth Trophic Level: made up of larger carnivores and omnivores (this is usually the last level)
  
• At each level detrivores are consumers that decompose dead organic matter
• Transfer of energy is not very efficient as energy is lost via life processes in organisms eg respiration, excretion, heat and movement
• This is why there is usually no more than four trophic levels
• Trophic structure can be illustrated as a trophic pyramid- each box represents a level and size indicates amount of energy stored in that level

• Within an ecosystem, nutrients are found in one of three stores: biomass, litter and soil
• Nutrients are transferred in a single cycle: soil to biomass to litter to soil and can be shown in a diagram known as the Gersmehl model
• Circle size represents proportion of ecosystem nutrients found at any given time in that store
• Arrow width shows nutrient flow as proportion of nutrients in store compartment
• Nutrients leave biomass store and are transferred by fallout into litter store where dead organic matter is broken down by decomposers and transferred by decay into soil store
• Nutrients come from precipitation and weathering from bed rock
• Nutrient losses come from runoff from litter and leaching from soil

Nutrient transfer affected by:

Climate: hot, wet tropical rainforests, rate of decomposition is high as well as leaching

Soils: acidic soils have fewer soil organisms and thus decomposition is quite slow

Vegetation Type: Leaves from coniferous trees take longer to decompose than those from deciduous trees