DarDarwin discovered the mysterious pattern that he called "closely allied" species. This means that similar creatures sharing basically the same body plan. These allied species tend to be found on the same continent or within the same oceanic islands even though there are species-by-species preferences for different habitats, food sources, or conditions of climate.
Darwin discovered that similar species occur nearby because they come from common ancersors. Paleontology revleas this clustering pattern too.
There are three major types of biogeography: Cosmopolitan, Endemic, and Disjunct. Cosmopolitan is not entirely cosmopolitan, endemic is restricted to particular regions, and disjunct is separated and rare (http://www.nyu.edu/projects/fitch/courses/evolution/html/biogeography.html)
During Darwin's visit to the Galapagos, he discovered three types of mockingbirds, all similar but living on different islands. He believed that this was because of inheritance.
The article compares the layers of rocks to animal or plant fossils. More recent layers of rock are on top of the older layers. The animal and plant fossils that strata contain, are very similar.
This article uses the tree porcupine as an example. The tree porcupine are closely allied species. One inhabiting the Eastern and the other in North America. (http://books.google.com/books?id=7HhIAAAAMAAJ&pg=PA36&lpg=PA36&dq=closely+allied+species&source=web&ots=sP7tsy5J3d&sig=dY_nvviNhZpsz2yxm
XrHIY17r4Q&hl=en#PPA36,M1)
In the article, Darwin explains that species that are closely related to one another is due to the fact that they have descended from common ancestors in a common nearby space.
Carolus Linnaeus showed how species can be grouped together and classified based on commonality
biogeology is the study of plans and animals over the surface of the earth (http://www.nearctica.com/ecology/habitats/biogeo.htm)
Darwin argued sequences were not just concidental. He believed that closely allied species succeeded one another in time, as well as living nearby in space because they are related throught evoluntionary descent.
Darwin wrote,"the embryo is the animal in its less modified state" and that state "reveals the structure of its progenitor." This was to explain that embryology could not be explained by conincidence.
Embryology is the study of formation and development of an embryo and fetus. www.britannica.com/eb/article-9001635/embryology
