Earth's oxygen levels are not enough for the animal to thrive.
 |
| Earth's atmospheric gases scatter blue light, image courtesey of NASA Earth Observatory |
Oxygen is considered vital to the survival of life on Earth, but recently scientists found elevated levels of oxygen in the Earth, it does not explain the appearance of the first animals.
This study shows that about 1.4 billion years ago there have been enough oxygen for animal life, more than 800 million years before the first animals appeared on Earth.
According to Emma Hammarlund postdoc and Professor Don Canfield, said that the Earth's available oxygen levels apparently not enough for the animal to thrive. Their research in collaboration with colleagues from the China National Petroleum Corporation and the University of Copenhagen, Hammarlund and Canfield have analyzed sediment samples from Xiamaling Formation in China.
Increased levels of oxygen Earth
It is estimated, animals evolved about 600 million years ago and is considered the later in Earth's history. The ultimate evolution of animal species explain the fact that oxygen is central to the respiration of animals, where this results in widespread idea that animal evolution associated with the final period increase in oxygen concentration in the atmosphere.
Many studies have difficulty in determining the oxygen concentration of the past. This study combines several approaches to break new ground in understanding the oxygen concentration that occurred about 1.4 billion years ago. Scientists use the distribution of trace metals to show that the waters where the formation of sediment deposited Xiamaling already contains oxygen. Distribution of biomarkers, molecules derived from ancient organisms, it indicates that the intermediate depth waters do not contain oxygen. Therefore, the formation Xiamaling buried in the oxygen minimum zone ancient period, similar to that currently found off the coast of Chile and Peru.
The scientists used a simple ocean models to estimate the minimum concentration of oxygen in the atmosphere needed to reproduce the distribution of oxygen in Xiamaling Formation. According to Canfield, the water column has an oxygen concentration of at least 4% of the current atmospheric level, this situation should be enough for the animal to thrive. By way of simple as Sponge (sponges) and worms, is now able to develop Atmospheric Present Levels (PAL) is less than 4% even much less. Sponge may resemble some of the first animals on Earth, if the species is growing by 4% oxygen content of Earth, it is likely that the first animals could also evolve with the same concentration or maybe even less than this value.
Then, why then animals do not thrive and late in Earth's history? Diversification of animals suddenly may be the result of various factors. Earth may increase oxygen levels do not so much concerned with animals revolution, as assumed.
Original articel: Enough oxygen long before animals rose
04 Jan 2016, by University of Southern Denmark via EurekAlert
Journal Ref: Sufficient oxygen for animal respiration 1,400 million years ago. Proceedings of the National Academy of Sciences, 2016; 201523449 DOI: 10.1073/pnas.1523449113
