Here he was able to find evidence for the elevation of reefs. Thus, through his comparison of a range of coral islands and other environments over a period of many months, Darwin was able to build a coherent theory. This was important, as the notion that one form of coral island might pass into another as the result of changes in the relative levels of land and sea represented one of his first flirtations with the ideas of gradualism - the significance of gradual change. A refuge for the destitute Charles Darwin used the term refuge for the destitute for the Cocos Islands. In it we see both the idea that the biota of remote islands is extremely depauperate and that of an assemblage of plants and animals thrown together as the result of long and difficult journeys.
Insects are very few in number .
He compared the poverty of the land biota with the fecundity of the nearby coral reef. Although the productions of the land are scanty he was later to write, if we look at the surrounding sea, the number of organic beings is indeed infinite . Interestingly, earlier in the voyage he had made a similar comparison between the biological poverty and desolation of the Falklands with the richness of the adjoining kelp beds. Significantly, too, he also compared the barrenness of East Falkland as it is now with the abundance and productiveness that existed in the remote past, for he had found a rock stratum that was packed with fossils. Darwin speculated about the manner in which organisms reached remote islands.