Energy Transformations

1. Energy Transformations Law of thermodynamics

2. Knowing your laws. • When looking at an example such as the energy which flows through a food chain, it is noticeable that the energy is transformed at each trophic level according to the needs and activities ( or better yet the “work” done) of the organism at this level. • Such energy transformations abide by two laws of thermodynamics.

3. Knowing your laws • Energy is neither created nor destroyed; it is merely changed from one form to another. • The total quantity of energy remains the same. Fist law of thermodynamics Second law of thermodynamics When energy is converted from one form to another some of it becomes degraded to a lower quality of energy. This degraded energy is less able to do work and in most conversions is released as heat.

4. Applying the laws to biological examples • The creation of cells require a high quality energy either from the sun or from other organisms. • As the energy flows through the ecosystem, there is a series of energy conversions and transformations. • At each trophic level, energy is lost to the environment through metabolic processes, waste and excretement. • Overall there is an increase in entropy at each step because low quality heat energy is released at each step in the chain. • In the biological system, an increasing degree of entropy results in the death of a cell or an organism, unless energy is restored. Living organisms restore their lost energy either directly from sunlight (as in green plants) or from their food molecules (as in other organisms). • The first law of thermodynamics also applies, as all of the energy within the organism in converted into energy within the organisms of the next trophic level, or into waste heat energy. • Which would explain why there is a limit to the number of trophic levels within a food chain.

5. Energy transformations • All energy found on earth originates from the sun, which is pure thermal energy transferred via radiation.

6. Examples

7. Examples • Examples of energy transformation • 1. Photosynthesis - in which green plants transform radiant solar energy into chemical energy that gets stored as potential energy in carbohydrates. • 2. Bioluminescence -in which chemical energy is transformed into light energy • 3. Conduction of nerve impulses - in which chemical energy is transformed into electrical energy • 4. Muscular activity - in which chemical energy is transformed into mechanical energy • Examples of energy transfer - A classical example of energy transfer in the living system is respiration. here, the chemical (potential) energy stored in respiratory substrates like glucose, is transferred to ADP and is stored in ATP. The ATP molecules transfer energy to other biological molecules.

8. Efficiency • When talking about the efficiency of energy conversions and transformations the ratio of energy input into the system eg. 1st trophic level to the useful energy output is examined. • The efficiency of the conversions between trophic levels in food chains varies between 5 to 20 %. • Energy efficiency % = useful energy output/total energy input x100