Energy flow

Topic 4.2

Essential idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.


What is the relationship between species, communities and ecosystems?

Levels of organization

3.5.U1 Most ecosystems rely on the supply of energy from sunlight

Energy through the ecosystem

3.5.U2 Light energy is converted to chemical energy in carbon compounds by photosynthesis

Light energy converted to chemical energy

3.5.U3 Chemical energy in carbon compounds flows through food chains by means of feeding

Chemical energy flow and feeding

3.5.U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat

Energy and heat from respiration

3.5.U5 Living organisms cannot convert heat to other forms of energy

Heat energy can not be converted

3.5.U6 Heat is lost from ecosystems

Heat lost to the enviroment

3.5.U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

Energy flows but nutrients cycle through an ecosystem

Energy enters and leaves ecosystems, but nutrients must be recycled. It is the presence of saprotrophic bacteria and fungi (decomposers) that recycle nutrients from the abiotic to the biotic component of the ecosystem.

Energy flows but nutrients cycle through an ecosystem
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Energy flow in ecosystems explained


3.5.S1 Quantitative representations of energy flow using pyramids of energy

The shape of an energy pyramid?

A pyramid of energy shows the flow of energy from one trophic level to the next in a community. The units of pyramids of energy are, therefore, energy per unit area per unit time, for example, kJ m-2 yr-1. The pyramid demonstrates that energy transformations between trophic levels are never 100% efficient.

Reasons for the shape of an energy pyramid
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