Complex sentence: The islands are known for their vast number of endemic species and were studied by Charles Darwin during the voyage of the "Beagle", as his observations and collections contributed to the inception of Darwin's theory of evolution by natural selection.
Split into simpler sentences: The islands are known for their vast number of endemic species and were studied by Charles Darwin during the voyage of the "Beagle". His observations and collections contributed to the inception of Darwin's theory of evolution by natural selection.