There is a awful lot of talk about the validity of evolution. However, ultimately, you must answer the question on the origin of the first cell. Athiest often stand with the random creation of desire molecules which align to create cell functions and eventually cells. If this is not your preferred method, you still have the same problem:
Where did the information come from?
That is, the information that governs the function of various cells to not only govern the cell, but for more complex organism, create the overall organism.
It has been shown(tested) that information between species is not different. Instead, the differences are when the information is activated creating the functionary part of the organism (tail, beak, etc). That stiill leaves the original question. Because in nature, information can be destroyed or lost, it can be exchanged, or manipulated (note the previous change in function of the info.). However, it still cannot be randomly (instantly or sporaticly) created.
This link will serve a point: http://www.randommutation.com/
On that site you can test the random mutation's inability to create new information randomly. You'll start with "The quick brown fox jumped over the lazy dog". The ability to change from this sentence to another is astronomically improbable. Also, remember, whenever a change results in a word being unreadable, that gene would be rejected. Some people think the change would be a word for a new word, but this sentence is much simpler than any genome, and real mutations are through manipulations of the original code.
So my second point is, if information mutation from one species to another is this improbable, show how that information ever originally combined into its original form.