Hi, igor.
Here is the entire theory of evolution in a nutshell:
1. Fact: Most breeding organisms produce more offspring than is necessary to replace themselves.
2. Fact: The population of most species are not increasing.
3. Conclusion: Most individuals must die before reproducing.
4. Fact: Many of the physical traits of individual organisms are hereditary.
5. Fact: Some traits make an organism more likely to survive and reproduce, while others make an organism less likely to survive and reproduce.
6. Conclusion: From 3, 4, and 5 we can conclude that organisms with the traits that make them more likely to survive and reproduce will produce offspring with those traits, while organisms with traits that make them less likely to survive and reproduce will leave few or no offspring with those traits.
7. Conclusion: A corollary of 6 is that as generations pass, the number of organisms with "good" traits will increase, while the number of organisms with "bad" traits will decrease, until eventually all individuals in the species will have the "good" trait and the "bad" trait will disappear altogether.
8. Fact: New heritable traits, usually subtle, occasionally appear.
9. Fact: These new traits do not appear in any predictable pattern; these traits can appear in any body part or instinctual behavior; furthermore, some of these traits are helpful to an organism's survival, and others are detrimental.
10. Conclusion: From 7, 8 and 9 we can conclude that a species will slowly "improve" with time, as new helpful traits appear and as the organisms with these traits are better able to survive and produce offspring with these traits.
11. Fact: There is no mechanism that is known to prevent these small, incremental changes from adding up, over time, to large changes; furthermore, there very few (if any) physical organs and instinctual behaviors in any species that do not appear in simpler versions in other species.
12. Conclusion: From 10 and 11 we conclude that there is nothing that will prevent very simple, primitive living species from producing the complex species that we see around us.
13. Fact: Occassionally separate populations of a species will become physically isolated from one another and cannot interbreed.
14. Conclusion: From 9 and 13 we conclude that these populations will evolve independently; from 12 we conclude that these will become different species.
15. Conclusion: From several interations of 14, we conclude that several species can have a common ancestor.
Everything that I have labelled as a fact is a fact; these facts have been observed and verified. Everything I have labelled as a conclusion seems to me (and to most people) reasonable conclusions based on these facts. What about all of this do you not think makes sense? More to the point, what here violates any known law?
I will end this post with evidence for the plausibility of evolution, and evidence for evolution having actually occurred.
16. Fact: Over the course of human history, animal and plant breeders have produce a huge variety of animal and plant breeds; many of these breeds share of common ancestor, and these breeds are often very, very different from one another as well as from the ancestor.
17. Conclusion: The appearance of random traits coupled with a selection process can result in evolution.
18. Fact: The species can be classified in a hierarchical pattern.
19. Conclusion: 15 and 18 allows us to conclude that all known species have evolved from a very few (perhaps one) ancestral species.