How do dinosaurs become extinct - Research Paper Example

How Dinosaurs Became Extinct. I INTRODUCTION A. DEFINITION Extinction refers to the of non existence characterized by the absence any living representatives. Extinction is captured by the death of the last species individual even though the ability of the species to breed and replenish could have gotten lost before this point. Extinction gets certified when there is no surviving individual that is able to create a new generation through reproduction. Functional extinction describes this state where only a countable few specie members survive, and can neither thrive nor reproduce. This could be as a result of age, lack of representation of both sexes and poor health and distribution. The actual point of extinction is difficult to identify due to the larger potential range that a species has, and the determination of extinction is usually done retrospectively. Dinosaur is a term that gets used to refer to a wide variety of chiefly terrestrial, carnivorous and herbivorous reptiles of the now extinct Ornithischia and Saurischia orders that thrived during the Mesozoic Era. They are thought to have been the biggest known land animals that shared a specific common anatomy. True dinosaurs had legs ankles and hips somewhat structured like a bird’s, such that the legs were mobile under the body and not outside like present lizard species. Sir Owen Richard formed the name dinosaur in 1841 to identify the remains of extinct reptiles. The name dinosaur originated from the Greek word deinos which means fearfully terrible, and sauros, which means lizard. Many explanations have been given, some of which have been convincing, about the extinction of dinosaurs. These explanations range from disease, volcanic eruption, asteroid impact, and climate change, which is the most supported of all theories (Page 56). II CASE PRESENTATION A. ASTEROID IMPACT THEORY The Asteroid Impact theory gets used by many scientists to explain the disappearance of dinosaurs from the face of the earth. As such, several variations of this theory exist, some of which are largely similar with minor differences setting them apart. The asteroid extinction theory gets sometimes referred to as the K-T Asteroid Theory, and the Alvarez Asteroid Impact. All these theories vary marginally, but are all centered on a single event though to have prematurely destroyed most of the life forms on earth dating back 65 million years ago (Norman 77). The asteroid theory got first fronted by the father son team of Walter and Luis Alvarez in1978. Walter and Luis analyzed sediment samples collected in the 1970s at the K-T layer close to the town of Gubbio in Italy. The tests revealed high concentrations of the element Iridium, rarely found on earth, but found in abundance in meteorites. Upon analysis of more sediment of K-T boundary strata from other regions of the globe, high concentrations of Iridium got recorded, as well. Guided on the basis of the average sediment thickness, team Alvarez suggested that a large comet or asteroid, perhaps several miles in diameter would be needed to spread as much Iridium as was recorded all over the earth. The impact of such an asteroid hitting the earth would be a massive explosion, massive fires and total annihilation of whatever life existed then, dinosaur inclusive (Parsons 95). A crater, partly submerged in water and worn down, got found along the Mexican Yucatan Peninsula whose creation largely coincides with the K-T boundary. Scientist from the world renowned National Aeronautics and Space Administration estimate that the Chicxulub Crater as it is currently known would have gotten formed as a result of the action of a 6 to 12 mile diameter asteroid. The crater is currently about 130 miles wide (Debus 66). Scientists from the Southwest Research Institute in Colorado have traced the asteroid path back into space. Their calculations revealed that a collision between an asteroid that was 100 miles wide called Baptistina, and another asteroid of relatively small size out beyond Mars’ orbit, shattered the bigger object sending its pieces into the inner solar system, about 160 million years ago. These pieces encountered earth 95 million years later and ended the dinosaur reign (Norman 100). Apart from the high concentrations of Iridium, scientists have identified the Chicxulub crater as evidence of the occurrence of the above events. They calculate that the crater got caused by a 10 kilometer wide comet or asteroid that was travelling at speeds of 30 kilometers per second, which is 150 times faster than the fastest jetliner. The presence of once molten rock pieces called impact ejecta, also give evidence of explosions forceful enough to melt bedrock rapidly and propel it to distances far from the origin. Impact ejecta that range in sizes from large chunks to tiny pebbles are a common phenomenon at and around the K-boundary (Parsons 96). Their case gets made even stronger by the presence of fractured crystals called shocked quartz, which depict a distinct pattern of fracturing associated with high energy explosions or impacts. The pattern is particularly prevalent in quartz found at and around the K-T boundary. Gradual decline in the dinosaur population, almost in the now you see them, now you do not manner suggests that something highly catastrophic must have happened to wipe out a whole species suddenly (Parsons 109). A different form of the asteroid extinction theory referred to as the K-T (Cretaceous-tertiary) Theory exists. It gets largely associated with the geological signature that is the K-T boundary, a thin sedimentation band found in many parts of the globe. K is the accepted abbreviation of the Cretaceous period while T is the accepted abbreviation for the tertiary period. Dinosaur fossils and remains are only located below the K-T boundary, suggesting that dinosaurs got extinct right before, or during this event. The number of dinosaur fossils located above the K-T boundary is few, and get reworked, a term used to mean eroded from the original location and later preserved in sediment layers. This, they argue, is proof that dinosaur disappearance can be linked to the impact of the asteroid falling on the surface of the earth (Barnes-Svarney 126). B. CRITIQUE OF THE ASTEROID IMPACT THEORY The Asteroid Impact Theory, whichever version one goes with, has had its fair share of criticism. Not all scientists got satisfied with the explanation of asteroid impact as the reason dinosaur extinction. These critical scientists point out that that record of fossils indicates that dinosaurs were on the decline way before the K-T boundary. Though they do not dispute that an asteroid might have fallen on the earth’s surface causing widespread damage, they are of the opinion that this asteroid might have been the last blow that wiped off the dinosaur population that was already vulnerable (Barnes-Svarney 131). At a dig supervised by renowned paleontologist Jack Horner in Montana, careful examination of fossil leaves and pollen obtained from a piece of the Hell Creek formation got undertaken. The hell Creek formation gets found just slightly above the K-T boundary, and it represents millions of years right before dinosaur extinction. Dr. Arens found out that the number of plant species, especially those that flower, significantly declined as one approached the boundary. A large portion of the flowering plant species had already long before the asteroid fell on earth. These scientists go ahead and argue that since these plants represented a significant supply of the herbivore dinosaur food and herbivore dinosaur were food for the carnivores, this could have led to a radical decline in the population of dinosaurs before the asteroid disaster occurred (Norman 97). C. THE VOLCANIC ERUPTION THEORY The Volcanic eruption theory has also been used to explain dinosaur extinction. Scientist that are of this theory have stated that the mantle plume that led to the rise of the Reunion hotspot made its way through the earth’s crust, creating a lava flood in Western India and the surrounding regions with Deccan traps flood basalts. The Deccan traps basaltic lavas eventually covered an enormous portion of India under successive lava flows thought to be horizontal. This converted the area into an enormous volcanic plateau (Page 102). Deccan traps were the result of the biggest volcanic catastrophe known, since the onset of the Mesozoic Era. Areas such as the Western Interior in North America, northeastern Asia, the Pacific Basin, and Peru also experienced massive volcanic activity. Just like the asteroid impact theory, the volcanic event gets thought to have led to massive destruction of the earth as it was known then, wiping all evidence of existing life, including dinosaurs. Volcanic eruptions bring with them massive dust clouds, sulphuric acid and toxic gases that hinder breathing. Volcanic activity could have caused drastic changes in weather, sunlight levels, and the hot lava could have caused wildfires (Officer 135). Many scientists have backed this theory over the impact theory because it is said to explain many facts that the latter cannot. The lava eruptions of the Deccan Traps in Western India got mentioned as a probable source of the iridium found in the K-T boundary. Proponents are of the idea that the possible explosive events associated with volcanic activity and out gassing could be sufficient enough to cause nuclear winter effect. This theory also explains the reasons behind the irregular distribution of iridium peaks. The fact that these probable volcanic eruptions covered a time span longer than an impact could be viewed as an explanation. It also accounts for selective extinctions of species and the possibility of how some organisms survived (Galagher 155). D. CRITIQUE OF THE VOLCANIC ERUPTION THEORY The Volcanic theory also has some loop holes in it. Opponents of this theory state that this theory does not hold water. First off, it is difficult to reconcile flows of lava in India with global wildfires because India as we know it is surrounded by water. It is highly improbable that the global wildfires would cross the water boundaries and spread to other areas. It is also worth noting that during this era, continents were getting pushed, and inland seas either got formed or retreated as a result of substantial ridge expansion. Shocked quartz has been found in a number of sites (Debus 119). This is inconsistent with that fact that grains of quartz obtained from a volcanic eruption are large and do not travel far. Massive flood basalts have been experiences at least three other times. No connection of mass extinction has been made in these instances, casting doubt on volcanic eruption as the cause of dinosaur extinction (Debus 124). E. THE DISEASE THEORY The disease theory proposes that during the crustaceous period, more land bridges began to appear on earth. The oceans began to dry, and the dinosaurs could move freely across the vast chunks of land. As the dinosaurs looked for food, they walked across land bridges and found relatives from way before continents drifted apart. Due to the new found interaction, there was massive spread of diseases. This led to a decline in the dinosaur population that ended up in extinction. A slight variation of the disease theory exists. Some scientists are of the idea that small animals could have been responsible for the demise of the large ones (Poinar 78). An Oregon State University zoologist, Professor George Poinar, believes that during the late cretaceous time, the number of insect species and population, many thought to be biting insects, increased rapidly. Examination of bugs from the dinosaur era revealed that these biting insects were carriers of diseases such as leishmania and malaria, which could affect reptiles and other animals. They also studied fossilized dinosaur excreta and found traces of nematodes, protozoa and trematodes that might have caused dysentery (Poinar 122). These scientists propose that the dinosaurs got intestinal parasites from insects that visited dung piles and transferred them to dinosaur foods. Prof. George also argues that the high temperatures and evolution of flowering plants made the late cretaceous period most suitable for the explosion in the insect population and the diseases they carried. It gets thought that due to lack of resistance to these diseases, the dinosaur population succumbed (Poinar 179). F. CRITIQUE OF THE DISEASE THEORY Many people and scientists alike have criticized this theory. They argue that in most cases, disease in a species is never fatal. If anything, it is appositive phenomena, as it leads to the death of the weakling members of the population, leaving the strong ones to survive, thrive and pass these favorable genes to the next generation. This should have been the case with regard to dinosaurs too. Whereas it could explain small die offs, this theory does not explain the disappearance of a multitude of species (Poinar 185). G. THE GLOBAL FLOOD THEORY The global flood theory states that dinosaurs became extinct as a result of global flooding described in the bible in the book of Genesis. Proponents of this theory pertaining dinosaur extinction front it as best fitting available information better than any other theory. This is because one of the great facts about dinosaur extinction is that a majority of key dinosaur fossil graveyards got caused by large amounts of water, suggesting that mass flooding must have been a principal cause of dinosaur death. For example, the 2007 discovery of a massive site of fossils in Lo Heco, Spain with estimated 8,000 fossils of dinosaurs got linked to heavy flooding by paleontologists from Cuenca museum. H. CRITIQUE OF THE GLOBAL FLOOD THEORY However, many have questioned the timeline associated with the global flooding that probably led to dinosaur extinction. In sharp contrast to the biblical view, naturalists hold that dinosaurs roamed the face of the earth more than 100 million years ago, and became extinct 65 million years ago, roughly 55 million years before humans inhabited the earth. The thought that humans and dinosaurs coexisted during the time of the global flood gets thought to be farfetched and historically inaccurate (Barnes-Svarney 186). I. CLIMATE CHANGE THEORY Many scientists believe that climate change in the Cretaceous period led to dinosaur extinction. They claim that the climate was largely tropical due to the fact that nearly all of the plants in this period were tropical plants. They believe that at the end of this period, temperatures dropped significantly. The plants that dinosaurs ate died off, and as a result, plant eaters including herbivorous dinosaurs also died. Carnivorous animals, including some dinosaurs also died due to lack of food occasioned by the death if herbivores. The decline in marine life, including marine dinosaurs, could also be attributed to death of planktons. The climate change theory though not conclusively explained could be a possible reason for the demise of dinosaurs (Poinar 177). This is so because the climate did change. Its effect on life system then is what is in question. J. LOGICAL CLIMATE CHANGE THEORY The logical climate change theory is more convincing than its climate change theory counterpart. It states that dinosaurs could not adapt to the ever changing environmental conditions at the time. This theory gets focused on earth’s environmental changes and dinosaur incompatibility to it. These changes got attributed to continental drift, a phenomenon that many scientists agree was happening at the time. Shifting of land masses brought with it dynamic change in the climate occasioned by differences in latitudinal temperature and differences in seasonal temperatures. It became either too cold or too hot for some part of the year, and less rainfall got experienced, leading to drying up of lakes and swamps. Upward, downward movements of the earth’s crust cold also cause changes in environmental conditions. This could explain the extinction of dinosaurs (Gallagher 197). III CONCLUSION SUMMARY Whereas scientists have come up with various theories to explain the disappearance and extinction of dinosaurs, it is only logical for a combination of these theories to be the causes of extinction. This is so because one cannot entirely write off another theory, especially if there is evidence that supports it. More studies ought to be carries out by scientists to come up with conclusive and accurate reasons that explain dinosaur extinction based on facts and truths.   Works Cited Charles B. Officer, Jake Page. The great dinosaur extinction controversy. Boston: Addison- Wesley, 1996. Debus, Allen A. Dinosaurs in Fantastic Fiction: Thematic Survey. Jefferson: McFarland, 2006. Gallagher, William B. When Dinosaurs Roamed New Jersey. New Brunswick: Rutgers University Press, 2007. George O. Poinar, Roberta Poinar. What Bugged the Dinosaurs? Princeton: Princeton Unversity Press, 2008. Norman, David. Fact Finder Dinosaurs. New York: Crescent Book, 1999. Parsons, Keith M. The Great Dinosaur Controversy: A Guide to the Debates. Santa Barbara: ABC-CLIO, 2004. Patricia Barnes-Svarney, Thomas E. Svarney. The Handy Dinosaur Answer Book. Canton: Visible Ink Press, 2010. Read More