Darwin observed different islands have different organisms.
Step-by-step explanation:
Darwin understood the process of evolution when he came across variety of organisms in the Galapagos island. According to Darwin there are variety of species. He observed different organisms as well as plants in different island, they adapt according to the climatic conditions.
He gave an example of tortoise where he said in one island there were tortoise whose shell was saddle shaped . On the other hand in another island there were tortoise who had shells which looked like dome shaped.