Understanding:
• Energy released from carbon compounds by respiration is used in living organisms and converted to heat
Energy stored in organic molecules (e.g. sugars and lipids) can be released by cell respiration to produce ATP
- This ATP is then used to fuel metabolic reactions required for growth and homeostasis
- A by-product of these chemical reactions is heat (thermal energy), which is released from the organism
Not all energy stored in organic molecules is transferred via heterotrophic feeding – some of the chemical energy is lost by:
- Being excreted as part of the organism’s faeces
- Remaining unconsumed as the uneaten portions of the food
Energy Transformations in Living Organisms
Understanding:
• Living organisms cannot convert heat to other forms of energy
• Heat is lost from ecosystems
The chemical energy produced by an organism can be converted into a number of forms, including:
- Kinetic energy (e.g. during muscular contractions)
- Electrical energy (e.g. during the transmission of nerve impulses)
- Light energy (e.g. producing bioluminescence)
All of these reactions are exothermic and release thermal energy (heat) as a by-product
- Living organisms cannot turn this heat into other forms of usable energy
- This heat energy is released from the organism and is lost from the ecosystem (unlike nutrients, which are recycled)
- Hence ecosystems require a continuous influx of energy from an external source (such as the sun)
Energy Transformations in Ecosystems
