Unit A

Module 1 ~ Lesson 1

 Earth's Solar Budget

Only 2% of the Sun's radiation is used in photosynthesis and passed on to consumers. The fate of the other 98% of the Sun's energy is depicted in the image. Although the energy absorbed by the Earth's atmosphere and the Earth's surface is not available for food energy, it is important in maintaining a temperature on Earth that allows organisms to survive. The albedo of a given surface describes the percentage of energy that is reflected away from the Earth's biosphere. The albedo of certain surfaces can help explain the climate in a given area. For example, sand has a much lower albedo than snow, meaning that sand-covered surfaces will absorb more of the Sun's radiant energy than a snow-covered one.

The first law of thermodynamics states that energy can neither be created nor destroyed; however, life on Earth depends on a continual supply of solar energy. This continual supply of energy is required because as energy is transferred, a portion of it is converted into a form of energy that is not usable to organisms, like heat. This is known as the second law of thermodynamics and has important implications for consumers.

Courtesy of McGraw Hill.


When you are done reading, click each row to view the answer and see if your answers are correct.
The albedo of fresh snow is 80% to 90%, while the albedo of water is 25 percent or less. Forests and grasses have even lower albedo values (7 to 18 percent and 18 to 25 percent, respectively). With the loss of snow and ice cover, which both have high albedos, more of the Earth's surface will have a low albedo. As the albedo of the Earth's surface decreases, less incoming radiant energy from the Sun is reflected by the Earth's surface. More radiant energy is absorbed, further warming the planet and reducing snow and ice cover.
As the skunk cabbage carries out cellular respiration and other reactions, it transfers energy to the environment as dissipated heat, which melts the snow around it.

The green arrow represents the cycling of matter. The yellow arrows represent energy, which is sometimes passed along to the next trophic level and sometimes lost as heat. As you can see the yellow arrow does not cycle like the green one. The second law of thermodynamics is represented by the loss of heat at each energy level.