Geologist: Geology and Isolation of Galapagos

Describe role: Early in Darwin's journey on the Beagle, he read the book by Sir Charles Lyell given to him by his former teacher, Professor Henslow, who recommended him for the job as Naturalist. The book, Principles of Geology, made him consider how geology and biology are intimately connected. How the land develops and where often determines what kind of animal and plant life will establish itself on the land. The geology that produced the volcanic islands, the Galapagos, played an important role in the kinds of strange animals that Darwin found there. Your job is to determine how these islands came to be, and how their geology played a role in the adaptations that various animals made to exist.

Background Information:

Charles Darwin Foundation with links to many animals, volcanoes, history, island information

Galapagos Island geology and diversity

Virtual journey with maps, atlas, history

Facts about Galapagos

Galapagos Archipelagos tour with island photos

List of islands on tour

Island map with information about each island

Geology of Galapagos Islands

Galapagos island tour, island photos

Link to volcanic hotspots

NSTA geology of the islands

 

You may also refer back to the sites listed on the Process page for information from Darwin's Journal, particularly the chapters covering Geology:

Voyage of the Beagle

Full text of Origin of the Species and Voyage of the Beagle

Report: You are to present your report in the form of a research paper to the Research Group (which will be the rest of the class). You are encouraged to use visuals...overhead transparency, photographs, or photos from the web to present your informataion. Each member of your team should have part in the presentation. You should be well organized so that you can present your report within 10-15 minutes. It is preferred that you not read the report but rather explain what you learned in your own words using an outline. Images from the Internet may be projected on our TV in our room if you have the URL.

As introduction to your report explain how the Galapagos Islands were thought to have originated, what they were like when Darwin first saw them, and how they differ from one another. Also provide information on their location and relationship to the mainland of South America. Based on their location to the mainland, how might the islands have been inhabited by the animals we now find living there?

You should include in the report responses to the following observations that Darwin wrote in his book, Origin of the Species:

"Although in oceanic islands the species are few in number, the proportion of endemic kinds (i.e. those found nowhere else) is often extremely large. If we compare, for instance the number of endemic ....birds in the Galapagos Archipelago, with the number on any continent, and then compare the area of the island with that of the continent, we shall see that this is true."

What does Darwin mean by this statement? What is the importance of this point?

"This might have been expected, for species arriving in an isloated district and having to compete with new associates would be eminently liable to modification and would often produce modified descendants....In the Galapagos Islands, of the 26 land-birds 21 are peculiar, whereas of the 11 marine birds only 2 are peculiar...."

Why might this be so? How does this information relate to the geology of the Galapagos?

"Oceanic islands are sometimes deficient in animals of certain whole classes, and their places are occupied by other classes: Thus in the Galapagos Islands, Reptiles, ...take or recently took the place of mammals." And in regards to plants, "in the Galapagos Islands the proportional numbers of the different orders are very different from what they are elsewhere. All such differences are generally accounted for by supposed differences in the physical conditions,...but facility of immigration seems to have been fully as important as the nature of the conditions."

Again what role did geology have to do with this?

Regarding relations of the inhabitants of islands to those of the nearest mainland,"The most striking fact is the affinity of species inhabiting the islands to those of the nearest mainland, without being actually the same....Why should the species which are supposed to have been created in the Galapagos Archipelagos and nowhere else bear so plainly the stamp of affinity to those created in (South) America?...It is an almost universal rule that the endemic productions of islands are related to those of the nearest continent."

How could you explain this phenomenon?

"The same law which has determined the relationship between the inhabitants of islands and the nearest mainland is sometimes displayed on a small scale within the archipelago. Thus each island of the Galapagos Archipelago is tenanted by many distinct species: but these species are related to each other in a very much closer manner than to the inhabitants of America."

Why would one expect this? Can you propose an explanation of how this might happen?