"In a system, a process that occurs will tend to increase the total entropy of the universe."
How, then, can evolution claim that the complexity of species is increasing? Doesn't this movement towards order violate the Second Law of Thermodynamics?
Such an argument is actually based on a misunderstanding of the law. The Second Law applies only to isolated systems, ones where there is no outside energy source. Thus, while the entire universe -- an isolated system with no net energy gain -- is moving towards disorder, parts of the universe may be influenced by outside energy sources. Evolution looks specifically at the Earth -- a system that is gaining energy from the sun. Because of this input of energy, the progression of living organisms towards order is not a contradiction of the Second Law, because the Earth is not an isolated system.
Furthermore, no one has ever successfully applied the Second Law to complex systems like living organisms, which themselves are more a collection of subsystems working together than a simple isolated system. The fact is that there are numerous examples of order arising from disorder in the natural world.
For more on the Second Law of Thermodynamics and how it relates to evolution, be sure to check out "Does thermodynamics disprove evolution?" in the Questions section at www.biologos.org.