Fact: Evolution obeys the Second Law of Thermodynamics for open systems.
Summary
The Second Law of Thermodynamics -- that closed energy systems tend to fall into disorder -- is not applicable in the case of life on earth. The earth is an open system, not a closed one, since it gets an endless supply of energy from the sun.
Argument
One of the most common criticisms of evolutionary theory is that it supposedly violates the second law of thermodynamics. This law states that in a closed system, disorder grows and less energy is available for work. A good example of this is a battery; it breaks down as it works, and, in fact, breaks down even when it is not working.
Evolution, on the other hand, appears to be doing the exact opposite: life is evolving from the simple to the complex, and everywhere we look we see increasing order, not disorder. The key to the creationist's confusion here is the forgotten phrase in a closed system. A closed system is one that receives no fresh inputs of energy from an outside source. An open system does. For example, consider a lava lamp. When a lava lamp is turned on, incoming energy in the form of electricity heats the base of the lamp. This creates a gas bubble out of the lava, which then rises to the top. This in turn drives the cooler lava down to the bottom, which then turns into another gas bubble. Soon a circular flow is established. There is a high degree of order to this open system. But turn the lava lamp off, and the circular flow stops. Without incoming energy, disorder grows, and all traces of a system disappear.
As for the earth, it is not a closed system. It receives an endless supply of energy from the sun, which fuels the life process and creates growing order. It may certainly be true that the universe as a whole is a closed system, and its stars will burn out billions of years from now, creating the disorder predicted by the second law of thermodynamics. But it is obvious there are variations at many local levels, including our own solar system. This subsystem should remain open for another 5 billion years, when our sun is predicted to die out.
Some creationists try to confuse the subject, with arguments along the lines of: "It doesn't matter if it's open or closed. The sun can shine a million years on a rock, but it isn't going to turn that rock into organic life." But this is a different argument, an argument of chemistry. The original argument was one of thermodynamics, which claims that there is not enough energy to fuel life's processes. We've just shown that there is; problems of chemistry are a different issue which should be addressed in separate arguments.
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