Some Christians have an unsophisticated interpretation of the Bible, particularly Genesis chapter 1, that leads them into conflict with the evidence of science. It is important to realise that this conflict is the result of faulty understanding rather than something fundamental to Christian belief. These people are usually called creationists and attack the evidence of biology that life developed by evolutionary processes and also in Astronomy (or maybe Cosmology) that the Earth and Universe are billions of years old.
This conflict is not inevitable as people with a sophisticated view of the claims of the Bible see no conflict with science.
Creationists are most strong in the US (they are much more weak in Australia) but for legal reasons have morphed to Intelligent Design (ID)to attempt to hide their religious motivation.
One of the arguments of ID proponents is that some parts of living organisms are so complex that they could not have developed by evolutionary means. Evolution, of cause, is blind, it does not know where organisms (or parts of organisms) will develop in the future. ID proponents claim that therefore evolution cannot work as the individual parts of an organism (or part of an organism) could not work on their own.
Evolutionary theorists have been aware of this issue for many years and have a straight forward answer: complex structures are developed from simpler ones, that had a purpose and function. The function of the individual sections did not necessarily relate to the final function of the large structure. It is one thing to propose this solution to the problem it is another to prove it, but scientists have demonstrated this fundamental idea in many areas.
One of the major arguments of ID is that the bacterial flagellum is so complex ("irreducably complex") that it could not have developed by evolutionary means. This claim has in the last decade been demonstrated to be incorrect.
The video below explains the issue more clearly than I could, and demonstrates that complex structures can develop from simpler ones.
The video above is just part of a talk. Here is the first section of the talk preceeding the video above:
Here is the second section:
Here are a couple of links to articles on this topic:
Rough Guide to Evolution
Creationism and Intelligent Design are wrong on two counts: they are bad theology and bad science