Thanoshi Balasuriya
Source: University of Exeter
Published: March 9, 2014
http://www.sciencedaily.com/releases/2014/03/140309150540.htm
Summary:
The common understanding is that the oxygenation of the ocean caused the development of animals. However, researchers have a new theory that the evolution of the first animals may have caused that oxygenation instead of the other way around. Of course, this oxygenation then did lead to more complex animals, but not the first animals. Sponges require very little oxygen, and therefore it was possible for them to have developed with the early Earth conditions. These sponges filtered out particles of organic material while pumping water out. This then lessened the demand for oxygen, since the ocean oxygen levels versus the organic material levels were now balanced, and thus the ocean was oxygenated. The productivity of the oceanic ecosystem was also reduced because phosphorus was no longer needed in the ecosystem, causing less oxygen to be needed, and therefore not trapped. Once the ocean became oxygenated with the help of these first animals, there were more suitable conditions for more complex, mobile animals to evolve and develop.
Connection:
In class, we learned that because of photosynthetic cyanobacteria, the carbon in the atmosphere was trapped, and oxygen was produced. This then led to the atmospheric oxygen levels to increase rapidly and the chemical composition of the atmosphere was predominantly oxygen based. Therefore, the first animals were able to develop and evolve, using the oxygen from the atmosphere. However, this article contradicts this theory about the evolution and development of the first animals. This says that instead of the first animals developing because of the high oxygen levels, the first animals actually themselves helped oxygenate the ocean, thus allowing for more complex animals to evolve and develop. These first animals were heterotrophic and used existing organic material in the ocean to help oxygenate the ocean, whereas in class, we learned that autotrophic photosynthetic organisms were the cause for atmospheric oxygen levels to be raised.
How is it evident that the first animals caused oxygen levels to increase? Are both theories of cyanobacteria and this article valid reasons for the rise in oxygen?
ReplyDeleteWell, sponges are thought to be simple enough to have been existent as the first animals before the cyanobacteria oxygenated the atmosphere. Sponges are able to filter water and take in organic material as they get rid of the excess water. Therefore, they managed to oxygenate the ocean, and the demand for oxygen was much less. Well, both theories are valid, but this new theory suggests that maybe the first animals existed before the oxygenation of the ocean, instead of having the oxygenation of the ocean being the reason behind the development of the first animals.
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