[frgoff]

Evolution doesn;t start with a puddle of amino acids and assemble a complete organism in one shot, but through multiple steps.

And that is the issue. Many biological systems must be assembled completely in one shot or they don't work at all; you can't assemble them in multiple steps.

[orionblamblam]

> Many biological systems must be assembled completely in one shot or they don't work at all...

Name one. The "Irreducibly complex" structures produced by the ID movement have all been shown to not be.

http://www.talkdesign.org/faqs/icdmyst/ICDmyst.html

My personal favorite are claims that wings are irreducibly complex.