Lecture 3 Energetics: Lecture Notes

Link to Lecture Notes part b (alternative notes… feel free to combine…)

Key topics for Energetics Lecture

Joules are the internationally recognized unit of energy (SI), calories are the non SI.

Laws of Thermodynamics
#1 Energy is neither created nor destroyed, only transferred and transformed. Heat is a form of energy.
#2 Energy always moves from areas of lower entropy to higher. (easier way to remember this: everything falls apart)

Continuous flow of energy drives life processes.

Laws of Thermodynamics unify the sciences, biology, chemistry, and physics

Entropy: (units Joules/K), the amount of dissipation of energy or the amount of disorder

Example: Dropping a stack of pennies. Spontaneous energy transformation will increase entropy, or amount of disorder.

Every object in universe emits radiation.
- As temp. increases, peak of this radiation emission shifts to shorter wavelengths.

Electromagnetic Radiation

  • Short-wave radiation vs. Long-wave radiation (e.g. thermal)
  • U-V
  • Visible Light
  • PAR, photosynthetically active radiation

Sensible Heat: kinetic energy in solids, liquids and gases, measured by thermometer, transferred through conduction and convection

Latent Heat: storage of energy in water vapor

Trophic pyramid, energy flows through the levels, example heterotrophs consuming autotrophs
- Generally only 5% - 20% of energy is passed up to the next trophic level

Transformation in energetics in the past couple of decades moving from energy, as expressed in Joules, to that of Carbon.

Redox reactions: Oxidation (losing electrons) versus Reduction (gaining electrons)
Examples: photosynthesis, respiration, decomposition, and fire, all involving carbon

Living things store energy in reduced compounds, oxidation occurs in metabolism

Respiration, breakdown of organic molecules: aerobic (with oxygen) vs. anaerobic (without oxygen)

Ecosystem: an open thermodynamic system that requires an energy source and a high-entropy energy sink

Sunlight heats the surface of the Earth and the Earth heats the atmosphere

Net radiation (Rn) A term for energy budgets, including sensible and latent energy, measured in Watts/meters squared
Equation: Rn = (1-rho)*St + Ld - Lu rho = shortwave albedo, St = shortwave radiation transmitted downward through atmosphere, Ld = longwave downwelling, entering system from above Lu = longwave upwelling, leaving the ecosystem into the sky
Nitrogen (please expand)
Nitrogen undergoes a large array of redox reactions that are biogeochemically and ecologically important

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