User:Kkennedy657/sandbox

Final Article Edits
All edits were made for the Cambrian Explosion page under the "Possible Causes of the Explosion" heading near the bottom of the page. https://en.wikipedia.org/wiki/Cambrian_explosion

Increase in oxygen levels
Cyanobacteria were the first organisms to evolve the ability to photosynthesize, introducing a steady supply oxygen into the environment.[110] Initially, oxygen levels did not increase substantially in the atmosphere. [111] The oxygen quickly reacted with iron and other minerals in the surrounding rock and ocean water. Once a saturation point was reached for the reactions in rock and water, oxygen was able to exist as a gas in its diatomic form. Oxygen levels in the atmosphere increased substantially afterward.[112]

Oxygen levels seem to have a positive correlation with diversity in eukaryotes well before the Cambrian Period.[113] The last common ancestor of all extant eukaryotes is thought to have lived around 1.8 billion years ago. Around 800 million years ago, there was a notable increase in the complexity and number of eukaryotes species in the fossil record.[114] Before the spike in diversity, eukaryotes are thought to have lived in highly sulfuric environments. Sulfide interferes with mitochondrial function in aerobic organisms, limiting the amount of oxygen that could be used to drive metabolism. Oceanic sulfide levels decreased around 800 million years ago, which supports the importance of oxygen in eukaryotic diversity.[115]

Complexity threshold
This genetic threshold may have a correlation to the amount of oxygen available to organisms. Using oxygen for metabolism produces much more energy than anaerobic processes. Organisms that use more oxygen have the opportunity to produce more complex proteins, providing a template for further evolution.[134] These proteins translate into larger, more complex structures that allow organisms better to adapt to their environments.[135] With the help of oxygen, genes that code for these proteins could contribute to the expression of complex traits more efficiently. Access to a wider range of structures and functions would allow organisms to evolve in different directions, increasing the number of niches that could be inhabited. Furthermore, organisms had the opportunity to become more specialized in their own niches.[136]

Oxidation of the Atmosphere and the Impact on Biological Diversity
The Cambrian Explosion was a major event in the evolution of complex life. Fossil records indicate a huge increase in the number of different species as well as an increase in the diversity among them. Multicellular organisms began to appear in significant numbers with more complex body structures and functions. Many theories have been proposed to determine the source of the diversity in the Cambrian Explosion and why it happened at that point in time. The appearance of atmospheric oxygen in significant concentrations during the Great Oxidation Event (GOE) seems to have a connection to this abundance of diversity (Sperling, 2013). Some organisms evolved the ability of aerobic respiration, utilizing the energy of the highly reactive oxygen in their environment. This trait was crucial in triggering the later boom in diversity. However, oxygen use alone does not directly lead to more complex structures and functions, but merely provides the opportunity for new proteins to be made (Dunne, 2008). Coevolution of organisms with aerobic respiration was the drive behind the manifestation of complex traits and the emergence of the great diversity seen in the Cambrian. The Great Oxidation Event marked a change in Earth’s atmosphere, starting around 2.4 billion years ago. Initially oxygen levels were only around one ten-thousandth of what they are today, but they were on the rise (Bekker, 2003). The source of this oxygen is thought to come from the evolution of photosynthesis in early cyanobacteria (Schirrmeister et. al., 2013). Cyanobacteria acquired mutations that allowed sunlight to be turned into energy. This trait would have had a huge fitness benefit and would have been selected for. Cyanobacteria introduced a steady source of oxygen into the atmosphere. However, oxygen levels did not increase substantially in the atmosphere until much later (Canfield, 2007). The released oxygen quickly reacted with the surrounding rock and other gases (Bekker, 2003). Atmospheric oxygen did not appear in significant amounts until a saturation point was reached and oxygen was able to exist in its diatomic form. Oxygen levels reached about 20% of what they are today shortly before the Cambrian Period (Canfield, 2007).

The production of oxygen likely caused a positive feedback loop in the development of cyanobacterial complexity. Oxygen is required to produce many different proteins, including collagen which is connects tissues together. Oxygen also provides the energy needed to produce and send various chemical signals between cells (Fairclough et. al., 2013). The Great Oxidation Event seems to coincide with the growth of multicellular cyanobacteria (Schirrmeister et. al., 2013). Not only did multicellularity arise, diversification of cyanobacteria increased greatly. The major clades of extant cyanobacteria seem to have emerged soon after the beginning of the GOE (Schirrmeister et. al., 2013). Multicellularity allows a whole new level of selection to operate on organisms, providing new ways to increase their individual fitness. Organisms had increased mobility, could take advantage of economies of scale, and even form differentiated cells, allowing division of labor. Multicellular cyanobacteria would have begun to spread and could produce oxygen even more efficiently (Schirrmeister et. al., 2013). Oxygen concentrations increased further, imposing selection on other species in the environment. Cyanobacteria began a chain of events that would have a huge impact on the future evolution of other species.

Oxygen is a highly reactive element, and thus a great source of energy. An oxygenated environment would provide early animals a template for their evolution (Canfield et. al., 2007). With the rise of oxygen in the environment, organisms that could withstand the toxic substance would have been selected for. Many microbes would have gone extinct, leaving behind a majority of microbes suited for an oxygen rich environment. Some organisms went a step further and evolved the ability to utilize oxygen to drive their metabolism. This allowed them to carry out chemical reactions that required more energy than anaerobic organisms could produce. This brought about the opportunity for larger, more complex structures that could be better suited for the environment (Sperling et. al., 2013). Furthermore, with more traits that could be expressed, there was an opportunity for evolution in different directions. Organisms had the opportunity to occupy more niches in their environment, becoming more specialized in their respective fields. Organisms with genes that allowed aerobic metabolism would have been selected for over anaerobic organism. Although aerobic respiration laid the foundation for innovate adaptations, these traits would not manifest unless other forces, mainly coevolution, were involved (Sperling et. al., 2013).

Oxidation from cyanobacteria has been shown to have an effect on the diversity of eukaryotes (Parfrey et. al., 2011). Some time after oxygen began trickling into the atmosphere, eukaryotes evolved aerobic respiration through a series of mutations. The last common ancestor of all extant eukaryotes is thought to have lived around 1.8 billion years ago. Diversification of eukaryotes in the fossil record, however, did not occur until around 800 million years ago (Parfrey et. al., 2011). This restriction in diversity is thought to be caused by the sulfuric environments in which the eukaryotes lived. Sulfide interferes with mitochondria in aerobic eukaryotes, limiting the amount of energy that could be used for structure and various functions. Oceanic sulfide levels decreased around 800 million years ago, allowing eukaryotes to begin using oxygen more efficiently (Parfrey et. al., 2011). This timing of increased oxygen usage lines up with the rise in eukaryotic diversity, suggesting oxygen does increase evolutionary complexity. Further evidence to support this claim comes from the Doushantuo fossil bed. Areas of the formation that were more oxidized during the Cambrian period were shown to have greater amounts of eukaryotic diversity (McFadden et. al., 2008). Due to the positive effect on both cyanobacteria and eukaryotes, oxidation of the atmosphere seems to be advantageous for the diversity of life in general. Oxygenation of the atmosphere alone cannot explain the extent of diversity that occurred in the Cambrian. While oxygen provided the means for more complex structures and functions, coevolution of aerobic organisms most likely caused the boom in diversity seen in the Cambrian (Sperling et. al., 2013). The presence of oxygen alone does not provide much direction for selection of specific complex traits. Interaction with other species is important in guiding the changes in traits. As one organism developed a new structure, such as larger size, other organisms in the vicinity were affected. The smaller organisms would have to evolve traits to help them compete with the larger organism for resources. These traits in turn would affect the original, larger organism, causing selection for another helpful trait that may have arisen (Fairclough et. al., 2013). This fits well with the Red Queen Hypothesis in that to keep up with the evolving organisms in their environment, organisms themselves had to evolve. None of these traits would have been able to be expressed in the first place if aerobic metabolism had not first evolved.

Eventually, aerobic organisms diverged from each other enough and more complex trophic relationships emerged. Interactions between different levels of predators and prey brought about even more evolutionary changes. Predators had access not only to biomass produced by their own aerobic metabolism, but also biomass produced by their prey (Dunne et. al., 2008). This provided an even greater basis to express traits that could be selected upon by the environment and improve their chances of catching prey. With so many adapted predators on the rise, prey now had a greater need for new traits to defend themselves. Much like organisms competing for resources helps bring about diversity, predator-prey interactions required the evolution of new traits to ensure the survival of both types of species. Organisms could occupy a much larger range of different niches than they could before (Dunne et. al., 2008). This put the organisms in a sort of evolutionary arms race and many unique traits arose as a result (Sperling et. al., 2013). Generations of interactions between organisms in this fashion could serve to explain the vast amount of species that arose in the Cambrian Explosion.

Future research could be conducted to test the effects of oxygen levels on complexity. Unfortunately, there are limited methods in gathering data about life from the Cambrian period, but fossils can still provide valuable information. There are bound to be more fossil beds much like the Doushantuo where relationships between oxygen and fossil diversity can be seen. Also, experiments could be run with species that are partially multicellular, such as slime molds. Perhaps in lower oxygen environments, slime molds may be at a disadvantage during their multicellular reproductive phase. Experiments that directly measure the effect of oxygen on complex functions would help shed light on its role in diversity.

The increase of oxygen in the atmosphere was an important event in the transition from simple, single celled organisms to a wide range of more complex, multicellular life. Cyanobacteria that evolved photosynthesis billions of years ago were responsible for the production of this vast amount of oxygen. Microorganisms developed a resistance to this highly reactive substance, and eventually some evolved the traits necessary for aerobic respiration. This laid the foundation for further complexity and diversification that was seen in the Cambrian Explosion. Utilizing the reactive energy of oxygen, aerobic organisms had the opportunity to produce a wider variety of substances that could be used in the expression of new traits. Once these new traits began to emerge, interactions between organisms allowed complexity to further develop. To compete with other organisms’ adaptations, organisms had to evolve their own unique traits to survive in the environment. This increased number of adaptable traits would cause a positive feedback loop that would result in even more unique traits. The root of this great diversity can be traced all the way back to the organisms that first evolved the ability of aerobic respiration. Oxygen can be seen as the spark that resulted in the complex system of life seen today.

Article Editing and Talk Pages
Information was added to the Great Oxygenation Event page at the very end of the "Timing" section. https://en.wikipedia.org/wiki/Great_Oxygenation_Event

With more energy available from oxygen, organisms had the means for new, more complex morphologies. These new morphologies in turn helped drive evolution through interaction between organisms.[10]

Sperling, Erik; Frieder, Christina; Raman, Akkur; Girguis, Peter; Levin, Lisa; Knoll, Andrew. "Oxygen, ecology, and the Cambrian radiation of animals". http://www.pnas.org/. National Academy of Sciences. Retrieved 1 October 2014.

At the very end on the talk page for Great Oxygenation Event, I added "Effects on Life" https://en.wikipedia.org/wiki/Talk:Great_Oxygenation_Event

Effects on Life
Oxygen started appearing in the atmosphere around 2.3 billion years ago, yet the Cambrian Explosion did not occur until much later around 550 million years ago. This page says oxygenation allowed diversification, but does not mention the time gap between the two. It would be helpful just to have a little clarification with that. Kkennedy657 (talk) 22:13, 1 October 2014 (UTC)

I added two sections to the talk page of Geological History of Oxygen https://en.wikipedia.org/wiki/Talk:Geological_history_of_oxygen

Source of Evolutionary Diversification
This page first suggests oxygenation was a driver for evolutionary diversification in the Cambrian period. Later, it says oxygenation is simply a prerequisite for the diversification. I think this just needs a little clarification. It seems oxygenation is more of a prerequisite. It brought about the opportunity for more complexity in a given speices, but the driving force for diversity seems to be coevolution. As more complex organisms began to appear, their interactions with each other required more adaptation. Kkennedy657 (talk) 21:53, 1 October 2014 (UTC)

Cyanobacteria
I feel some more info on the photosynthetic organisms would be helpful. The first photosynthetic organisms used sulfuric compounds with oxygen as the waste product. Cyanobacteria eventually developed photosynthesis that used water as fuel and while still expelling oxygen. The cyanobacteria had a new, more efficient way to photosynthesize. This made cyanobacteria the main producer of atmospheric oxygen. Kkennedy657 (talk) 22:32, 1 October 2014 (UTC)

Project Topic and Bibliography
I will be researching the rapid diversification of early life that came as a result of the Great Oxidation Event. This topic is quite important in evolutionary biology because many believe this event helped spark the rise of multicellular organisms as we know them today. Early organisms’ adaptation to use oxygen as a means to produce energy gave rise to many evolutionary opportunities. Organisms now had better physical means to express their genetic code. Virtually all multicellular organisms alive today utilize aerobic respiration and it’s all thanks to the early organisms that adapted to oxygen.

1) Butterfield, N. 2007. Macroevolution and macroecology through deep time. Palaentology, 50: 41-55. http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2006.00613.x/full This article describes relationships among organisms in the Pre-Cambrian and Cambrian periods. It draws differences between the earlier, simpler organisms and their more complex descendants with distinct ecosystems. It shows how oxygenation was most likely precursor to initial diversity, but also brings up the coevolution of the organisms. As more species came about and interacted, evolutionary changes in one species could directly or indirectly cause changes in another. I want to use this article to help show oxygenation is at the root of the success of this coevolution. Oxygenation brought about different organic compounds that translated to different traits in organisms. Predation gave organisms the opportunity to acquire some of these compounds without having to generate them. These new compounds, in turn, shape the evolution of the predator and the cycle continues.

2) Knoll, A. H. 2003. Life on a young planet. Princeton, NJ, and Oxford: Princeton Univ. Press.

This book contains much information on the Cambrian Explosion. It gives insight on the evolution of species at the very beginning of this time period and how they diversified. Evidence is provided through fossils records in rock cliffs. The different sediments in the faces of the cliffs provide geological timelines fossils. This creates a convenient illustration of the different species that lived throughout this time. The lowermost parts of the cliffs have fossils from simple, single cells organisms. As the elevation increases, not only do more species appear, but there is evidence of behavioral complexity through tracks and burrows. I plan to use this source to provide facts, including timelines, about the Cambrian period. This will help create a clearer picture on the specific diversification that occurred and how quickly it happened.

3) McFadden, K., Huang, J., Chu, X., Jiang, G., Kaufman, A., Zhou, C., Yuan, X., Xiao, S. 2008. Pulsed oxidation and biological evolution in the Ediacaran Doushantuo Formation. Cambridge, MA: National Academy of Sciences.

This article describes a potential coupling between oxidation and evolution. Connections are drawn between the oxidation of the oceans during the Ediacaran period and chances to the natural carbon cycle. The Doushantuo Formation in China, which has remarkably well preserved fossils, is studied in this article. When it was covered with water, the fossil bed varied in oxygen levels and species distribution depending on location. The article goes into detail on the different organic and inorganic materials present and how organisms of that time interacted with them. I will use this article to help show how different oxygen levels seem to lead in the evolution of different species in the fossil bed itself. I will show how oxygen changed the materials organisms had at their disposal and how this affected their livelihood.

4) Perkins, S. 2009. Atmosphere took roller-coaster ride around time of Earth’s oxygenation. Washington, DC: Science News.

This article provides some timelines for the Great Oxidation Event and how oxygen levels were determined through chromium isotope ratios. The large amounts of oxygen were likely introduced by photosynthetic miccroorganisms like cyanobacteria. There is evidence that atmospheric oxygen came about long before the GOE, however the concentrations were very low and didn’t surge until the GOE. The oxygen levels did not remain constant, but instead have fluctuated over a few billion years with the last rise around 550million years ago. I will use this article to give some general information on the Great Oxidation Event. Comparing this to the information from the Cambrian period will help show how the differences in oxygen levels affected life and it’s direction in evolution.

5) Sperling, E., Frieder, C., Raman, A., Girguis, P., Levin, L., Knoll, A. 2013. Oxygen, ecology, and the Cambrian radiation of animals. National Academy of Sciences.

This article shows a link between oxygen levels and food web complexity. Low oxygen levels correspond to lower proportions of carnivores, whereas higher oxygen levels tend to result in more complex and diverse food chains. This has a deep impact on evolution as more diverse food chains help bring about more variety in organisms. I plan to use this to show that oxygen does indeed have a direct impact on carnivore fitness and diversity how it is a contributing factor to the diversity in the Cambrian. Oxygen allows greater body size in organisms and this alone could have a huge impact on diversity.