Coyne classifies two types of islands, continental islands and oceanic islands (page 100) Evolution uses these two types of islands to point out that the oceanic islands that are missing similar types of species so if a creator had made all the animals everywhere than this wouldn't be the case. Coyne then goes on to explain that this is an example of the "blend of chance and lawfulness" (page 109) of evolution when distributing life on earth. First, define the two types of islands. Then find examples of species that are found on main lands and continental islands but not on oceanic islands. Explain how oceanic islands can be considered to always have been separated hence why evolution of certain species did not occur there when the well established principle of pangea is accepted as truth. If all of the land was once together than wouldn't evolution occur similarly on all of the land that broke off? Not just some of it? Doesn't calling evolution a blend of chance and lawfulness give support to Creationism? If evolution is one large part chance that we do not explain in a scientific way then isn't there a gap open for divine intervention? How is it chance that the birds migrated to the Galapagos islands, they must have had a scientific reason for leaving where they came from in the first place and another reason to stay on the island therefore how is that chance at all? Use examples in your explanation.
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Continental islands are islands that were once part of the continent, but became separated due to “rising sea levels or by moving continental plates.” Examples include “the British Isles, Japan, and Madagascar.”
ReplyDeleteOceanic Islands were never part of the continent, and arose from coral reefs or volcanic eruptions. Some examples are “the Hawaiian islands, the Galapagos islands and St. Helena.”
Species that are found on continental islands but not oceanic islands are “freshwater fish, amphibians, reptiles and land animals.” Continental islands like Great Britain have all of these types of species because it was once connected to the continent; these animals could have lived in the land mass that would become Britain after Pangaea broke up. On the other hand oceanic islands like the Galapagos islands, where Darwin studied, only have “birds, plants and insects.” This is the case because after the formation of the islands, various factors, including bird flight and wind currents, may have blown seeds and insect eggs or birds may have settled down to nest, which caused the isolated evolution of these species. The other types of animals, “freshwater fish, amphibians, reptiles and land animals” cannot easily migrate to the island (only amphibians may be able to reach close islands). The probability of a fish (egg) surviving a journey, probably a large storm, to an island without its normal source of food, either plankton or smaller fish, is incredibly small. Amphibians, reptiles and land animals would have to swim to the island, expending large amounts of energy that could be put to much better use. However, aquatic animals, like the monk seal, can live and travel to islands like Hawaii, but this is the only aquatic mammal that Hawaii has, making the occurrence of any sort of mammal on an island rare. (100-101)
Evolution would not necessarily continue in a similar fashion on an island like Britain than France, unless the conditions that selected traits were very similar for a species.
The “chance” that Coyne talks about is basically a random selection of what species live where. He notes that the “currents, winds and opportunity to colonize” are all factors that are vagaries that randomly distribute speices. For example Coyne says that the lemur would not have existed if it had not moved to the area that became Madagascar before it separated from the mainland. By “lawfulness” he means that there are certain predictable rules that species will follow, he cites invasive species, saying that they will always stay in a less competitive and stressful environment. (110)
Invasive species usually are able to survive much better than established species, who have developed a delicate balance in the ecosystem. The cane toad, for example was introduced in Australia to cull a population of crop destroying beetles. (Wikipedia) These toads spread rapidly and forced the Australian government to institute programs to kill the toads. Thus the first bird species on an island with no other, or few competitors can easily survive and reproduce, thus creating a disadvantage on the mainland, where there is probably more competition and a more restricted niche.
http://en.wikipedia.org/wiki/Cane_toads_in_Australia
Continental Islands: "[land masses] once connected to a continent but later separated by either rising sea levels that flooded former land bridges or by moving continental plates." (Coyne, P. 100)
ReplyDeleteOceanic Islands: "[land masses] that were never connected to a continent; they arose from the seafloor, initially bereft of life, as growing volcanoes or coral reefs." (Coyne, P. 100)
There is a slight misconception in your logic about what you believe Pangea to be. "Pangea was the supercontinent that existed during the Paleozoic and Mesozoic eras about 200 million years ago, before the component continents were separated into their current configuration." (1) As you can see, Pangea was an ancient arrangement of CONTINENTS. Continental islands broke off from the actual continental land masses (as I previously stated), so the flora and fauna of continental islands should be extremely similar to their adjacent continents.
The brown bear is native to Japan, specifically
the island Hokkaido (4). The brown bear is found in much of Northern Europe and Asia, and even North America. However, there is no creatures similar to the brown bear on oceanic islands, like Hawaii. This observation makes perfect sense because the Hawaiian islands have never been connected to any continental land mass so the brown bear cannot have wandered there. Additionally, the brown bear cannot swim across an ocean, so that way of travel for him is barred. It is reasonable to assume that there was no way for a brown bear to reach an oceanic island without treading some sort of land bridge (which don't exist near oceanic islands), and that is why there are no brown bears found on oceanic islands.
However, since oceanic islands are formed at sea by active volcanoes (more information in link 2), they have never actually been a part of any continental land mass. Pangea is an arrangement of the 7 continents, but no where does it say that Pangea contained ALL the land that is present in the world. Kaua'i, the oldest island in the Hawaiian archipelago is only 27.1 MYA (2), so there is no way it could have been part of Pangea.
Given that oceanic islands were never part of Pangea, and therefore subject to different circumstances, evolution would proceed differently on oceanic islands than it would on continental islands or continents themselves.
Also, another misconception in your question is about chance. You seem to believe that evolution happens randomly. However, this is not the case. In evolution, chance refers to the possibility certain genetic information that betters an organism's chance for survival will be passed down. Natural selection, the idea that drives evolution in itself is NOT random chance. In fact, natural selection as defined by Richard Dawkins is "the non-random survival of random variants" (Coyne, P. 119). Mutations themselves do not occur randomly. They are the results of selective pressures presented to an organism by the environment. Natural selection is a force that takes genetic information found in an organism, and changes it in such a way that it helps the organism better suit its environment.
ReplyDeleteThe only part of chance that influences bird migration is birds being randomly swept out to sea by storms, or birds sitting on drift wood that eventually, randomly, drifts to an island.
Moreover, birds are not the only organisms swept out to sea randomly. Charles Lindbergh exposed microscope slides while on his transatlantic flight and captured many critters hundreds of miles from land (Coyne, P. 105). Some of these insects were being carried by wind currents, so undoubtedly, some will eventually be carried on to an island.
The migration of birds can be easily explained by science. As stated on wikipedia's article about migration, "Bird movements include those made in response to changes in food availability, habitat or weather." Birds migrating to any island or different section of land can be justified by the drive to survive. If an ecological niche is open to be colonized, for any species, it is reason enough to move and adapt to this new environment. Just like how whales moved back to aquatic environments from terrestrial ones, birds migrate to islands (such as the Galapagos) in prospect of new food, and an open ecological niche, which would provide a maximum chance for survival. The longer an animal lives, the more it can reproduce thus greatly increasing the chance that the genes of the organism will be passed down.
1:http://en.wikipedia.org/wiki/Pangea
2:http://www.hawaii.edu/environment/ainakumuwai/html/ainakumuwaiislandformation.htm
3:http://en.wikipedia.org/wiki/Bird_migration
4:http://en.wikipedia.org/wiki/Wildlife_of_Japan
5:http://en.wikipedia.org/wiki/Brown_bear