One argument creationists Intelligent Designists”Whatever they call themselves now” people use is that certain systems are so complex that without all of the pieces available the system could not exist.  This means that the system couldn’t have evolved because without all the pieces the system can not function; enter the phrase: irreducible complexity and the idea that evolution is disproved.  These Scientists moral advocates claim that bacterial flagellum is a great example of this.

This wiki article is pretty complicated and discusses flagellum with detail that complicates the whole issue pretty quickly.  A site that seems to break down the information a little better is this one.

The bacterial flagellum consists of 3 major domains: an ion driven motor, which can provide a torque in either direction; the hook, a universal joint which transmits motor torque even if it is curved; and the filament, a very long structure which acts as a propeller, and behaves differently depending on which way the motor turns.

There are quite a few parts that make up bacterial flagellum.  If irreducibly complexity is correct, when these parts are separated they have no function.  About 5 years ago this issue was unanswerable.  This is not the case anymore.  What scientists are finding is that there are pieces of the flagellum that are grouped together.  These groups when separated have been found in other systems and species where they do operate by themselves and are an entire system with a specific function.

One of the major problems with ID is it’s lack of scientific data.  This appears to stem from the fact that those involved with ID try to force their theories into text books and classrooms rather than use the scientific process.  And because of this, many scientists are unwilling to take the theory seriously.

A great resource for this and other information is:
YouTube of all places!  The following is a video of Ken Miller’s talk on Intelligent Design at Case Western University. Ken Miller discusses this issue as well as the whole ID movement.