The second law of thermodynamics says no such thing. It says heat won't spontaneously flow from a colder body to a warmer one, or equivalently, that total entropy (a measure of useful energy) in a closed system won't decrease. This doesn't prevent increasing order because
the earth isn't a closed system; sunlight (with low entropy) shines on it and heat (with higher entropy) radiates off. This flow of energy, and the change in entropy which accompanies it, can and will power local decreases in entropy on earth.
entropy is not the same as disorder. Sometimes the two correspond, but sometimes order increases as entropy increases. [Aranda-Espinoza et al, 1999; Kestenbaum, 1998] Entropy can even be used to produce order, such as in the sorting of molecules by size [Han & Craighead, 2000].
even in a closed system, pockets of lower entropy can form if they're offset by increased entropy elsewhere in the system.
In short, order from disorder happens on earth all the time.
The only processes necessary for evolution to occur are reproduction, heritable variation, and selection. All of these are seen to happen all the time, so obviously no physical laws are preventing them. In fact, connections between evolution and entropy have been studied in depth, and never to the detriment of evolution [Demetrius, 2000]. Some people see the evolutionary increase in diversity and the origin of life as entropy-driven [McShea, 1998; Schneider and Kay, 1994].
Creationists themselves admit increasing order is possible. They introduce fictional exceptions to the law to account for it.
Creationists themselves make claims that directly contradict their claims about the second law of thermodynamics, such as hydrological sorting of fossils during the Flood.
Aranda-Espinoza et al., 1999. Electrostatic repulsion of positively charged vesicles and negatively charged objects. Science 285: 394-397.
Kestenbaum, David, 1998. Gentle force of entropy bridges disciplines. Science 279: 1849.
Han, J. & Craighead, H.G., 2000. Separation of long DNA molecules in a microfabricated entropic trap array. Science 288: 1026-1029.
Demetrius, Lloyd, 2000. Theromodynamics and evolution. Journal of Theoretical Biology 206(1): 1-16. http://www.idealibrary.com/links/doi...jtbi.2000.2106
McShea, Daniel W., 1998. Possible largest-scale trends in organismal evolution: eight live hypotheses. Annual Review of Ecology and Systematics 29: 293-318.
Schneider, Eric D. and James J. Kay, 1994. Life as a manifestation of the second law of thermodynamics. Mathematical and Computer Modelling 19(6-8): 25-48. http://www.fes.uwaterloo.ca/u/jjkay/..._as/lifeas.pdf
This is an attempt to claim that the second law of thermodynamics implies an inevitable increase in entropy even in open systems by quibbling with the verbiage "left to themselves." The simple fact is that, unless "left to themselves" means "not acted upon by any outside influence," disorder of systems can decrease. And since outside influence is more often the rule in biological systems, order can and does increase in them.
That the claim is false is not theory. Exceptions happens all the time. For example, plants around my house are left to themselves every spring, and every spring they produce order locally by turning carbon from the air into plant tissue. Drying mud, left to itself, produces orderly cracks. Ice crystals, left to themselves, produce arrangements far more orderly than they would if I interfered. How can a trend to disorder be invariable when exceptions are ubiquitous? And why do creationists argue at such length for claims which they themselves can plainly see are false?
Disorder and entropy are not the same. The second law of thermodynamics deals with entropy, not disorder (although disorder defined to apply to microscopic states can be relevant to thermodynamics). There are no laws about disorder as people normally use the word.