Monday, April 5, 2010

Continental Biogeography: Before and After

Coyne tells the story of the Norwegian explorer Roald Amundsen who froze to death with his party in 1919 after “their unsuccessful attempt to be the first at the South Pole” (99). He continues to compliment their recognition of the Glossopteris fossils they found. In addition, Coyne provides a map of the supercontinent that shaped the world during the Permian period (98). First, describe how the theory of biogeography applies to evolution in the context of continents. Then, explain how the example of the Glossopteris fossils supports this theory. Predict why evolutionary pressures affected the Glossopteris fossils more than they did to other animals that currently live in Antarctica. Finally, consider the modern African continent, which is slowly being pulled away from Europe and Asia due to plate tectonics; predict the region of Africa this will most strongly affect evolution in and how?


  1. Biogeography applies to evolution because it shows the dispersal of species over a region. There were two theories that encompassed biogeography and those were religion and creatures moved across the earth. Both these theories use the continents to show how animals moved across land. The religious view is more hard to understand on how these creatures were able to colonize the earth when the continents were spread apart. In order to understand biogeography we need to imagine the world when the continents were one huge subcontinent called Pangea. Geologists found similar creatures living on opposite sides of the world. How is it possible for a creatures that are similar able to colonize opposite sides of the earth? This is why Pangea is important because the creatures migrated to different continents, and as these continents started moving further apart, the creatures had to adapt to the environment. These species then evolved a certain set of characteristics that sets them apart from their relatives. Evolution helped with the species develop these characteristics because the species needed to survive. Then natural selection wipes out the species that didn't get the adaptation in that environment because the creature is not able to survive due to the fact that they are easy prey, or etc.
    Then the Glossopteris fossils support the theory because it shows how these trees were able to make it across the ocean. These trees have heavy seeds in which they are not able to cross the ocean. When we put the continents together into Pangea, then we see how these fossils were distributed, and the way that they are placed on a map makes sense. If the continents were left as they are today, then these dispersals of these fossils would not make sense because as I stated, their seeds are really dense, and would not be able to make it across the ocean. Referring to the explorer, these fossils were a major importance of evolution when they found them next to his body because it shows how the dispersal of these fossils with the continents explains continental drift and evolution. Antarctica has no nutrients to support trees, and the only way that the fossils could have got there would be if Antarctica was once connected to South America and Africa.
    The evolutionary pressures affected the Glossopteris fossils the most because as I stated, Antarctica has no means of supporting life, (except for the animals that live in cold weather environments). These fossils were not able to grow, and they were very well preserved. They did not have the right conditions to adapt to the environment.
    Though I would have to disagree with the last part of your statement. The African plate is moving north-east into the the Indian Plate,and therefore the Eurasia plate. (Source below). The region that the drift would affect would be the entire continent, but mainly the northern part in the dessert. What I'm about to state is assuming that the continent is completely shifted to the north. If this was the case, then the entire continent would experience the change because creatures would have to evolve new adaptations, and natural selection would favor the ones with the best ability to survive. There would be drastic climate changes that these creatures would have to adapt. Thats why I'm saying that the north would be the most greatly affected of all because its temperatures would plummet, and most of the creatures that were used to the extreme heat would go extinct.


  2. Biogeography is the distribution of biodiversity over space and time. This idea contributes to evolution in major ways. It helps explain how it is possible for there to be different types of animals that have similar forms in different places. This would not be possible unless the continents started out connected by bridges ie. the Bering land bridge. One large land mass allowed animals to roam and expand their boundaries. This explains why similar, present day animals (in similar environments) have similar looking fossils of their ancestors. As the continents separated, the dispersed animals would begin to adapt to different environmental changes and thus, look different than their common ancestor.
    The example of Glossopteris fossils supports this idea. The fact that the Glossopteris was considered deciduous suggested that its habitat was in temperate areas with cold winters. Looking at modern dispersal, this wouldn't make sense since fossils were found in South America, South Africa, India, Australia, and Antarctica. However, if one considers the situation in light of Pangea, it is simple to understand how they could have spread to these continents. As they were all connected, the glaciers moved outward from Antarctica. Therefore they would have provided the necessary cooler climate for the Glossopteris to survive.
    Evolutionary pressures may have affected the Glossopteris more than animals of Antarctica most likely because Antarctica cannot support much life. As it is greatly covered in ice, only primitive forms of plants and animals inhabit the continent. Life flourishes in the surrounding waters, but they would not be as affected because they are not constrained to one area.
    As Africa is being pulled away from Europe, evolution will occur (assuming Africa is completely separated so there is no land bridge for animals to travel). Depending on where Africa is moving, animals will have to adapt because they can no longer travel to Europe and because temperatures may change. Most life is used to tropical weather or a hot environment. If these temperatures are altered, species will need to adapt or become victims of natural selection. Northern Africa would be most effected because it is the area where there was the most traffic of species going to and from the connected continents. The rest of Africa would be affected by the previously stated conditions despite the fact that they remain mostly in the continent already.

    Why Evolution is true