Discuss 2 different types of typical items that are fossilized: (1) a bone (2) fossilized organic material, what objects fossilized the best? What characteristics of the object influenced this?
Bones are fossilized through a process referred to as permineralization. The burying of bones underground leads to water flowing into the bone. With the assistance of microbes, ground water decomposes some of the original organic material in the bone. Gradually, water occupies the empty space created in the bone tissue. As a result, new minerals fill the spaces in the bone. It eventually reaches a point where all or some of the original bone minerals are dissolve and replaced by newly-deposited materials (Brasier, et al., 2015). Thus, petrification/replacement is the process through new materials/mineral replace original minerals in fossilized bones.
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Organic materials/substances decompose through carbonization. It is the process through which organic matter is converted into carbon or carbon-containing residue through destructive distillation or pyrolysis. With the help of water, organic material of the animal of plant is transformed to a thin film of carbon (Brasier, et al., 2015). Gases such as oxygen, hydrogen and nitrogen ae driven off, leaving an outline of the fossilized organism.
Comparing between fossilization of bones and organic matter, bones fossilize the best. The reason is because hard materials such as bones or shells easily become fossilized compared to soft tissues such as organic matter. In many cases, organic material is destroyed by microorganism and scavengers. However, bones can easily survive physical and natural biological processes thereby undergoing fossilization process such as compaction, replacement or chemical alteration. The characteristic that makes it possible for bones to fossilize is the hard skeleton that slows down the decomposition process and prevents scavengers and microorganisms from interfering with the process of fossilization.
Discuss 2 different types of typical media: (1) mud (2) bog. How did the characteristics of the medium (i.e., the dough) influence fossilization?
Mud is the soft sticky matter that is formed from a mixture of water and earth. On the other hand, Bog is a region comprising of wet muddy ground that can hardly support the weight of a substantially heavy body. Archeologist describe mud and bog as the best mediums for fossilization (Javaux, 2006). As a matter of fact, majority of fossils are found in sedimentary rocks. The sedimentary rocks are formed from accumulation of sediments such as mud and sand. Bogs are especially known to provide the best conditions for fossilization. Plant and animal remain found in peat bogs are known to be remarkably well preserved, some have been found with preserved hair, organs and even skin.
The medium in which fossilization takes place has great influence on the process. It must provide the optimum conditions or characteristics that would encourage fossilization. One of the conditions is complete cut off from oxygen. The body must be quickly covered by sediment after death with unchanging mechanical and thermal conditions. Considering a medium such as land, it does not offer the optimum condition for fossilization since it has highly changing mechanical conditions. It is also exposed to erosion than deposition. Land also has a huge concentration of oxygen which is detrimental to the fossilization process. However, considering a medium such as mud, especially on the ocean floor it provides the best conditions for fossilization. The fine sediments of mud effectively block oxygen from reaching the body. Bodies are quickly covered by layers of sediment that are continuously deposited and builds up over many years. The continuous deposition weighs down on the bodies of dead organisms applying the necessary pressure and heat, which lead to imprinting on the animal remaining as a fossil and forming sedimentary rock. The characteristics that make bogs a perfect fossilization medium is the high acidity levels of the anoxic waters. High concentrations of fluvic and tannic acids in the bog regulate bacterial activity and have low oxygen concentration to prevent decomposition.
Based on your answers to the above questions, what type of organisms would you expect to be the most commonly preserved? What type of environment is most conducive to this preservation?
Observations from the previous question seem to indicate that aquatic organisms with are the most likely to be preserved/fossilized. Fossils of land animals are scarce or highly scattered since land does not provide the optimum conditions for the process of fossilization. After dying, their bodies are usually consumed by other organisms or decompose. However, the likelihood of aquatic organism becoming preserved is high because a watery environment especially one with high acidity and low oxygen concentration provides the optimum conditions for the preservation of the body. For preservation to occur the animal must die in a watery environment and end up buried under the silt or mud. Watery environments have the capability of even preserving the bodies of soft-bodied organisms by protecting them from decomposition (Skinner, 2005). The probability of a land animal dying in a watery environment is low. However, almost all aquatic animals die in the watery environment. Due to this basic requirement, land creatures have very little chance of becoming fossilized but majority of aquatic creatures are preserved.
Organisms that die in watery environments are commonly preserved due to certain characteristics of that environment. The bodies of organisms that die in lakes or seas travel to the bottom of the water bodies. In most lake and seas, the water at the bottom is normally stagnant, hardly mixes with surface waters, and has no dissolved oxygen. Thus, when an aquatic animal dies the body sinks to the bottom of the ocean where their no oxygen and rapidly covered by the stagnant muddy bottom thereby getting preserved. Such kind of optimum conditions are not only found in the lakes and sea but in bogs and muddy regions. The conditions are appropriate for preservation of fossils since water slowly seeps through mud compared to sand (Wallace, 2011). This ensures that the body does not decompose fast. Other types of organic matter often trapped in mud compete with the fossils for the limited oxygen. Another condition of watery environment is the acidity that effectively kills or minimizes the activities of bacteria and other microorganism that decompose dead organic matter.
How do you think your findings show a "bias" toward certain organisms in the fossil record?
My observations definitely show a bias against certain organisms in the fossil record by arguing that it is mostly the aquatic organism that get fossilized. According to fossil records; aquatic, land and air animal have equally been found preserved. Some have existed for thousands of years. Archeologists discovered the fossil of a mosquito dated 36 million years ago. A mosquito is not an aquatic nor a land organism. The recommendations made about preservation reveal obvious bias. It is stated that for a body to become a fossil, it must not decay into nothing. Rather it must be preserved in specific medium (mud or bog) that usually happens to be water. Additionally, it is stated that the body must stay there under pressure and undistributed in order for the organism to materialize and transform into fossil (Dave, 2012). However, it is obvious that other organism (land or air) that have hard body parts such as shells or skeletons stand a better chance of fossilizing compared to some aquatic organisms such as jellyfish or slug. Such organic materials are hardly destroyed by other organism and decay at a much slower pace than most aquatic organisms. Therefore, the argument that preservation occurs in a watery medium is not well founded since certain organic materials are able to withstand decomposition despite being in unfavorable preservation conditions.
What information can fossils tell us about Earth's past?
Fossils provide a way of piecing together mysteries about the Earth’s past. They tell us about the transformation/evolution of various forms of life over a long period of time. For instance, fossils show that certain types of fish began developing small leg-like limbs. Those organisms were the earliest ancestors of the amphibian-like land animals. The fossils records show proof of evolution of birds from reptiles and evolution of modern humans from early primates. Fossils also provide history of life on earth. For example, archeologists have identified fossils that are close to 3.4 billion years old (Michelle, 2015). These fossils. Such fossils are compared against fossils claimed to be of the earliest humans. Information from fossils shows that humans have been on Earth for a comparatively less period of time since fossils belonging to the earliest humans are about 250,000 years old. Fossils record provide information about organisms that previously roamed about the Earth’s surface. Were it not for the preserved fossils, it would be impossible to know about organism that existed in the Earth’s past, i.e. mammoths, dinosaurs, etc. Fossils records also demonstrate the structure of Earth billion of years ago. Information derived from the fossils shows that the Earth is quite different from how it looked like many years ago. For instance, fossils of reptiles and plant from Antarctica are not consistent with the extreme cold climate of Antarctica. However, such fossils are similar to fossils found in other landmasses that seemed to have been connected with Antarctica (Michelle, 2015). Such fossil records illustrate that in the past, the whole Earth must have been joined together.
References
Brasier, M. D., Antcliffe, J., Saunders, M., & Wacey, D. (2015). Changing the picture of Earth's earliest fossils (3.5–1.9 Ga) with new approaches and new discoveries. Proceedings of the National Academy of Sciences , 112 (16), 4859-4864.
Dave, H. (2012, Aug 17). Bias in the fossil record . Retrieved from The Guardian : https://www.theguardian.com/science/lost-worlds/2012/aug/17/bias-fossil-record
Javaux, E. J. (2006). Extreme life on Earth—past, present and possibly beyond. Research in microbiology , 157 (1), 37-48.
Michelle, Z. D. (2015, Oct 8). Fossils help scientists build a picture of the past—and present . Retrieved from Smithsonian Insider : https://insider.si.edu/2015/10/fossils-help-scientists-build-a-picture-of-the-past-and-present/
Wallace, A. R. (2011). The geographical distribution of animals: with a study of the relations of living and extinct faunas as elucidating the past changes of the earth's surface (Vol.1). Cambridge University Press.
Skinner, E. S. (2005). Taphonomy and depositional circumstances of exceptionally preserved fossils from the Kinzers Formation (Cambrian), southeastern Pennsylvania. Palaeogeography, Palaeoclimatology, Palaeoecology , 220 (1-2), 167-192.
