Sunday, March 28, 2010
Significance of Biogeography
On page 88, Coyne discusses how biogeographical is such strong support for evolution that Creationists simply pretend that biogeographical evidence doesn't exist. Creationists' theory for the current distribution of species is that two of each species hopped on a ship for 6 weeks, and got off magically at different spots of the word. In contrast, Darwin proposed that specific species distribution occurred because species of plants and animals dispersed, evolved, and then land physically changed. Explain what aspects of this hypothesis are correct and not 100% accurate. What discoveries and developments of technologies have occurred since Darwin that would support his theory? How does this biogeographical evidence support evolution? Why is this evidence so powerful when compared to say, fossil evidence? In your answer, make sure to discuss both continental drift and molecular taxonomy and how they relate to this topic.
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Darwin’s theory, that the distribution of species resulted from dispersal followed by evolution, was correct, and has only been supported by recent discoveries. The only thing that Darwin could not have taken into account, due to lack of evidence at the time, is the occurrence of continental drift. Continental drift, or the movement and separation of the ancient supercontinent, explains how the ancestors of similar animals, such as ostriches, rheas, and emus, could have dispersed to different continents in the past (Coyne 90).
ReplyDeleteMolecular taxonomy, a relatively recent development in technology, also supports Darwin’s theory by tracing the genetic divergence of living species from their common ancestors. Molecular taxonomy is more reliable than the fossil record, which is incomplete and requires a specific type of environment to allow fossilization to occur (Campbell 510). Due to molecular taxonomy, we can relate the divergence of species to the movement of continents.
A more recent version of dispersal can be seen in island biogeography, from the ecology unit. The number of different species on an island is proportional to the size and proximity of the island to the mainland, which affects the dispersal rate. Closer islands have a higher rate of immigration due to the increased probability that animals will reach the island from the mainland (Campbell 1216). In addition, continental islands have a greater diversity of life because they were once connected to the mainland, allowing animals such as mammals, reptiles, and freshwater fish to disperse to the land before it became separated from the mainland (Coyne 100). Oceanic islands, on the other hand, typically have fewer species of mammals and reptiles because those species are less able to disperse to the island. The resulting speciation on these islands supports the theory of evolution, since the species adapted to suit their ecological niche.