Lecture 3 Energetics: Background (Odum)

Ecology: A Bridge Between Science and Society
Eugene P. Odum, 1997

Odum expresses the concept of Energetics “as the common denominator in ecology and the link between ecosystem and economic system" (H.T. Odum 1971, 1973, 1996; Odum and Odum 1981)

Energy Units
Calorie, Watt, Joule, Erg, BTU, Horsepower, etc. were created to quantify specific kinds of energy. There is a movement to create and use an international unit of energy for all types of energy.
• calorie (c) is a gcal, or the heat required to raise one gram water by one degree Celcius.
• Calorie (C) is a kcal, or the heat required to raise on kilogram water by one degree Celcius.
• Joule is work energy required to raise one kg to height 10 centimeters (~ 0.24 gcal)
• watt is one joule per second
• kilowatt-hour (kWh= 1000 watts/hour) is about 860 kcal.
• kilojoule (KJ= 1000 joules) is widely used as an international unit in ecology, approximating 4.2 kcal or 1 BTU
There is currently not a way to compare the qualities of energy, such as the difference between a 100 Cal of sunshine verses 100 Cal of gasoline.

Energy Laws
Behavior of Energy described by Laws of Thermodynamics, http://en.wikipedia.org/wiki/Laws_of_thermodynamics

To survive and do well, ecosystems require continuous input of high-quality energy, storage capacity, and the ability to dissipate entropy. Odum describes these three features as the maximum power principle, or the systems most likely to survive are those that efficiently transform the most energy into useful work for themselves and surrounding systems with which they mutually benefit.

James Lotka (1880-1949) introduced thermodynamics to ecology, calling it “physical biology.” His thesis stated the organic and inorganic world functioned as a single system with all parts so intertwined that one must understand the whole system to understand its components. He applied this theory to the ecological system as a major functional unit of the biosphere (independently deduced by biologist Tansley).

Solar Radiation is in the middle range of the electromagnetic radiation spectrum, having visible light, ultraviolet and infrared light. Ozone shield is the layer of O3 molecules in the upper atmosphere, which prevents ultraviolet light from reaching the earth’s surface.

Threats to the Ozone Shield- Products such as CFCs break down the ozone shield, producing the ozone hole over Antartica in 1984.

The Radiation Environment at Ground Level
Organisms at or near the Earth’s surface are immersed in long-wave heat (thermal) radiation from nearby surfaces, such as soil, water, vegetation, and clouds. Colorless gasses trap CO2, creating a “greehouse effect.”

Energy Flow through the Biosphere
A large part of solar energy flow is dissipated into unavailable heat (not wasted), driving the hydrological cycle and powering weather systems.

Energy Concentration: eMergy
Energy’s “quality” increases as it becomes more concentrated through transformations. A quantitative term to denote energy’s “quality” was proposed as eMergy. Embodied energy also describes this quality measure.

Primary Production- the amount of organic matter converted from solar energy by autotrophs in a given area for a given period of time, expressed at some rate.

Source-Sink Energetics- when excess organic production from one ecosystem (source) is exported to a less productive ecosystem (sink).

Kinds of Photosynthesis- basic process is oxidizing:
Carbon dioxide+ water+ light energy = carbohydrate+ water+ oxygen
The carbohydrate forms other organic matter.

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