Natural selection is life. What survives and breeds passes on it's genes. What doesn't doesn't.<quoted text>
1 Prove that natural selection exists, in an objectively verifiable manner via the scientific method.
2 - What it is exactly and how that was determined in an objective manner via the scientific method.
3 - The mechanisms it used to do whatever it is you think it did, how it used them, when it used them, and how all this was determined in an objective manner via the scientific method.
All the young of a species are slightly different (That's random).
Most die (Watch any nature film).
Some are going to be better at surviving in their particular environment than others. They're the ones most likely to survive and so pass on their genes. This results in a species becoming more adapted to that environment.
In a different environment different young might survive and passing on different genes changing the species as it adapts to different conditions.
There are a vast number of different strategies for survival. Some survive by being bigger or faster. Other's by being smaller and quieter. Worms and slugs thrive by living out of sight or being distasteful to eat. All that matters is that some survive and breed.