Evolution by natural selection.
Thousands of sea turtle eggs are laid each season,
but less than 10% survive to adulthood, and fewer will find a mate and reproduce.
Darwin observed that many organisms produce more offspring than can survive to reproduce.
He proposed natural selection as the process that allows a few individuals with
"favorable variations" to survive and reproduce - and pass on those
"variations" to offspring.
Over time, accumulation of favorable traits results in adaptation of organisms to their environment.
The long-term result is evolution of new species: an ancestral common ancestor
may yield offspring that evolve into separate species.