Paleontology and Earth History - Essay Example

PALEONTOLOGY STUDY QUESTIONS By and Task a The Archean period was characterised by an atmosphere that people and animals would not be able to inhabit today. The air was full of methane, ammonia and a myriad of other poisonous gases that would not support life today. In other words, the atmosphere is thought to have lacked free oxygen. The Archeon is a geologic eon that preceded the Proterozoic Eon and one that spanned 1,500 Ma (million) years. All life before this period was bacterial, limited to single-celled organisms that did not have even a nucleus, they were called Monera, a name that later changed to Prokaryota. It is important to note that having the free oxygen in the atmosphere that became abundant as this period progressed means that life could now evolve into something complex, at least organisms with a nucleus. Task 1 b Scientific evidence show that life did not begin at least about 3.5 billion years ago. During this time, most of the life forms were simple bacterial that had no nucleus. Also, all the first organisms were single-celled and it was until over two billion years, the period that we have the Archaean that life evolved more. This explains why there was no complex fossils of organisms found in rocks well until about 580 million years ago (Knoll et al. 2006). In other words, life forms had already been in existence before the Archaean. Throughout this period however, fossils of the cyanobacteria mats, also referred to as the stromatolites that are said to have been instrumental in the creation of the free oxygen we have today existed. Other than that, this period had biogenic graphite that was found in a number of metasedimentary rocks in Western Greenland aged 3700 Ma. Apart from this, fossil records show that there were also sandstone that was later discovered to have microbial mat fossils in the Western Australia dated 3480 million years ago. Other chert beds contain bacterial fossils making this period one that contributed a lot to the evolution of living things from the simple organisms to more complex life forms. Task 2 Climate is one of the many factors that make life on earth possible. Within millions of years, the temperatures of the earth have changed to fit bounds that are life-sustaining. The icehouse interval is characterised by three major glaciations in the Phanerozoic Eon. The first one is the Late Ordovician that occurred about 430 million years ago, the second one is the PermoCarboniferous period whose period spanned 325-240 million years ago and lastly the Late Tertiary which started about 35 million years ago and up to now (Koeberl 2009). The icehouse is controlled by a number of factors, rather hypotheses that try to explain what controls the icehouse. One of them focuses on the position of the pole in which case it argues that there cannot be any ice sheet formed on continents when they are near the equator and that the same can only be formed near poles. The cool temperatures during the aforementioned three intervals were as a result of low sea levels, less photosynthetic activity, low levels of carbon dioxide in the atmosphere, and of course less volcanic activity in the oceans (Fischer 1986). There are a number of important factors that scientists have agreed on as having been influential during the icehouse period. These controlling factors are secular which means that they are internal to the earth, or cyclic, external to the earth (astronomical that is). Task 3 The Ediacaran period spanned between ca. 635 to 542 Ma. Fossils from this period of time have been found from all over the world and are largely of multicellular organisms. However, the organisms, which are said to comprise a group of the Late Precambrian fossils, were first found near the Ediacara Hills of Australia (the place where they actually got their name from). The Ediacaran organisms resemble the invertebrates such as the arthropods, worms, echinoderms, or the cnidarians. Nonetheless, there are other fossils that are very different from the morphology of most known fossils. Scientists argue that these must be fossils of organisms that were evolving on their own (Skelton, Spicer, & Rees 1997). Still, it is possible that these were organisms that truly lived, and did not evolve into other organisms and rather became extinct. While most people would argue that the Ediacaran organisms were animals, this cannot be for sure since no one has been able to establish clearly where the organisms fit in the tree of life. Some argue that they were intermediates between animals and plants. The Ediacaran organisms resembled tubes, discs, quilted mattresses, and some mud-filled bags. The fact is that such morphology does not resemble any of the organisms we know today and it can therefore be understood why some paleontologists argue that the organisms may as well represent a group of extinct organisms. The very first accepted organism from the Ediacaran is the Charnia, which was initially thought to be a relative of the sea pens. Task 4 Today, there is a huge debate on whether the Ediacaran organisms were either of the five kingdoms we know today. Knoll (2003) notes that “the preservation window throw which we view the Ediacaran biology also closed”. In other words, while most paleontologist would refute the possibility that the organisms helped pave way for the different life forms we have today, others refute the authenticity of the organisms themselves. In other words, there are those who say that the Ediacaran organisms were not even organisms. To date, very little information is known about the organisms. However, while there are those who challenge the fact that these were organisms, research continually shows that a high level of evolution had already been achieved during the Precambrian time as the fossils show that the Ediacaran organisms were not only multi-celled but some may have had a skeleton. Also, these organisms mark a time where atmospheric oxygen was available and thus the period where more evolution was expected to occur. While the extinction of the Ediacaran fauna was initially thought to have been caused by grazing of other skeletal organisms, recent study shows that the changes in the sea level must have played an immense role in their extinction. A very famous paleontologist, Guy Narbonne, postulates that it is possible that the Ediacaran organisms still exist today, in the form of mollusks and warms. Task 5 The Great Oxidation Event (abbreviated as GOE) was a period that marked an increase in the amount of oxygen in the atmosphere from the less than 1/1000, 000 to between 0.2-2 per cent (Melezhik 2013). This happened about 2400 million years ago. The only possible ways any particular gas can increase in the atmosphere are dependent on the production of the gas and its loss. In the Great Oxidation Event, the source of the Oxygen gas must either have had a flux or there was an oxygen gas decrease of its sink flux. The two events must have created an imbalance and thus the production flux of the gas exceeded how much oxygen gas was used and which therefore led to a gradual increase to the amount we have today. The most known evidence of the great oxidation is the definite increase in size of animals that could only rely on oxygen for their survival. The amount of oxygen that was there during the Ediacaran period may not have been a lot but at least the levels marked the evolving of multicellular organisms that could only depend on oxygen for respiration. Initially, the atmosphere had no free oxygen. In this case, the only life forms that could exist in such harsh environments were only bacterial. The continuous organic carbon burial is said to have contributed a lot to the GOE as it resulted to a tipping point where the levels of oxygen gas exponentially rose. Task 6 The Cambrian explosion is also referred to as the Cambrian radiation, a period that was marked by appearing of major phyla. The period began approximately 570 million years ago. Life, on the other hand, had itself began over 3 billion years ago. While the “explosion” may not have been instantaneous, it clearly market the origin of most (although not all) animals than we see today. In a matter of fact, the “explosion” lasted over a period of thirty million years. The changes in the environment are what lead to the diversity of the animal and plant kingdom as we see them today. During this period, the level of oxygen rose. The increase in oxygen to sufficient amount was responsible for the evolution of the single-celled organisms into the multicellular and complex organisms there are today. As discussed above, the Ediacaran period occurred right around this period and it marked the existence of the Ediacaran organisms, organisms that thrived in the increased levels of oxygen in the atmosphere. Geological changes that saw the weathering of rocks into the ocean and thus the release of minerals into the environment brought about biomineralisation, which is the incorporation of minerals into living organisms to form structures such as the bones, teeth, exoskeletons and shells. The hard parts were very important in allowing organisms to grow into larger bodies, consider the importance of teeth in an animal. Task 7 Palaeotemperatures are the temperatures of a given place in a given geological time. To reconstruct the surface palaeotemperatures requires a number of methods. If paleontologists are interested in the reconstruction of the marine sea surface temperatures (commonly abbreviated as SST), for instance, this could be done through solving a number of equations. One method employs the use of isotopic values of oxygen in Foraminifera shells. On measuring of variations of ?18O (which is the mean value of Globigerina bulloids in the isotopic oxygen during late winter to early spring of the SSTs) in the calcareous shells shows a representation of the sum total of ?18O variation in the ocean water. The correlation coefficient used in this measurement is =0.69 and then the Globigerinoids ruber used is the mean of late summer to autumn in an isotopic equilibrium. Since the isotopic composition of oxygen in the water is highly dependent on the levels of evaporation of the sea water, ?18O variation is therefore a good method to use as most of the results reflect changes in fresh water budget due to the continental ice volume. Reconstructing of the surface palaeotemperatures shows that during the LGM, temperatures were at least 2o C lower that they are today in the late spring and winter. Task 8 One of the main occurrences of the Ediacaran-Cambrian interval were changes in the amount of oxygen in the atmosphere. There are a number of ways through which oxygen can be influential in determination of the kind of animals that would roam the earth during that time. To begin with, no animals would exist if there were no oxygen in the atmosphere. To say the least, every animal today depends on oxygen for respiration. Without oxygen, it is particularly difficult or rather impossible that even an ant exists. During this period, the GOE occurred. At this point, there was a substantial increase in the amount of oxygen in the air. While there is no explanation as to the timing of the increase in atmospheric oxygen and the animal disparity and diversity that the planet saw during this time, it is clear that the increase in oxygen in the atmosphere played the most significant role in the diversification of the animal kingdom. The level of oxygen before this period were as low as 0.1 per cent and therefore very unfavorable for any existence of a complex organism. Complex animals need more oxygen for the metabolism processes taking place in their body. If the oxygen levels increased, therefore, then it was possible to have the single-celled organisms evolve into multicellular ones. This only happened during the Ediacaran-Cambrian interval. Task 9 Global warming is definitely among the things that have had the world really troubled. With the increasing industrialization has brought about pollution to deal with, and most of which is emission of carbon dioxide gas and other greenhouse gases into the atmosphere. The level of carbon dioxide in the atmosphere is increasing. Some hundreds of years back, there were no coal-powered industries and many automobiles like there are today. Without the industries, the levels of carbon dioxide in the atmosphere was low and global warming was therefore not a risk. When studies started documenting the melting of icecaps and the rise in sea level, a shift toward the real threat greenhouse gases posed on the planet became important. Today, companies are going green and campaigning for clean energy is in every government’s agenda. Although the levels of carbon dioxide may not increase suddenly, it is evident that the rate at which the world climate is changing is alarming and that the carbon dioxide levels in the atmosphere will continually increase at least for the next few years. This is because industries are continually being constructed, cars are increasing on the roads, and oil and coal will not be replaced by any other type of fuel until the wells are dry. References Erwin, Douglas H., and James W. Valentine. The Cambrian Explosion: The Construction of Animal Biodiversity, 1999. Knoll, Andrew H., et al. "Eukaryotic organisms in Proterozoic oceans." Philosophical Transactions of the Royal Society B: Biological Sciences 361.1470 (2006): 1023-1038. Knoll, Andrew H. Life on a Young Planet: The First Three Billion Years of Evolution on Earth. Princeton, N.J.: Princeton University Press, 2003. Koeberl, Christian. The Late Eocene Earth: Hothouse, Icehouse, and Impacts. Boulder, Colo.: Geological Society of America, 2009. Melezhik, Victor A. Reading the Archive of Earths Oxygenation. Berlin: Springer, 2013. Skelton, P. W., and Bob Spicer. Evolving Life and the Earth. Bletchley, Eng.: Open University, 1997. Read More