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英国Paper代写:The correlation between modern birds

2019-01-10 | 来源:51due教员组 | 类别:Paper代写范文

下面为大家整理一篇优秀的paper代写范文- The correlation between modern birds,供大家参考学习,这篇论文讨论了现代鸟类和恐龙。羽毛曾被误认为是鸟类独有的特征,但数百万年前,羽毛就被发现是恐龙的功能部件。另外,拉希德的研究也揭示了人们如何通过独立于化石记录的实验来探索古代进化的发生方式。证实突变的积累确实是早期鸟类尾巴截断的最可能的原因。但鸟类物种是由恐龙突然突变而来的想法是错误的,相反,是累积突变使鸟类发生了的爆炸性进化。

correlation between modern birds,鸟类和恐龙,论文代写,essay代写,paper代写

Based on the findings from fossil records, the correlation between modern birds and dinosaurs has been established for years. However, there are still missing links in the process of evolution. According to Ksepka (2014), “Birds are a group of feathered animals with a unique body-plan adapted to flight.” In this paper, three of the unique features of birds are identified, which are body sizes, feathers and tails. An analysis of each of the features will be provided, in an attempt to explain what happened during the evolution process from dinosaurs to birds. With the establishment of bird-like features, the early birds are found to be on a much faster track of evolution, compared to other lineages of dinosaurs (Ksepka 2014). The explosive evolution should not be seen as a sudden event, but an accumulation of mutations only possible after the establishment of the three features, among many others.

Although feathers are regarded as the most identifiable feature in the distinction between dinosaurs and birds, the evolution of size is even more crucial in the development of flying abilities. Research by Ksepka (2014) has revealed that the body size of ancient bird had undergone rapid reductions. Such reductions have granted these birds advantage in adapting to the changing climate, and are the fundamental element in the evolution path from dinosaurs to birds. Like many other bird-like features, the reduction in body size had begun long before the actual evolution took place. It was a much-needed change for the survival for some dinosaur species, granting them advantages of an alternative and less competitive habits and even changed body functions and improved prolificacy. The evolution of birds after body size reductions can be described as a burst, which is a clear distinction for other lineages of dinosaur evolution. In many ways, the earliest birds share many common features with their non-avian theropod contemporaries. However, the acquirement of a smaller body size marked the turning point, where more rapid evolutions and diversifications among the bird began (Ksepka, 2014). Smaller body sizes were crucial in the development of flying abilities. Although ancestors of bird with much larger sizes were also able to fly through gliding, a special ratio must be reached between wing size and body weight for real flying, which was only possible through size reductions. In addition, smaller sizes may have enabled ancient birds to climb onto trees, which became their shelter and source of food. Despite the different views on the precise time the body size evolution accelerated, it is commonly agreed that size was the break through factor in the dinosaur-bird evolutions (Ksepka, 2014)

Feathers are often regarded as a structure of birds only, since it distinguishes birds from other vertebrates. However, little was known about the origin of bird feathers until recent years. It has now been established that feathers are not exclusive to birds, but are found in early dinosaurs that were non-avian as well (Zhou, 2014). In fact, the original function of feathers may not be flying related at all. When feathers first started to appear on dinosaurs, its main purpose was to keep the warmth, which explains why the entire body surface of dinosaurs are covered in feathers. Another purpose of the feathers is for the looks that attracted more females. The colorful feathers served as a display in the pre-mating activities, as well as effective camouflage from potential danger. Thus, despite the irrelevance to flight, the feathers were a highly functional part of the early dinosaurs. With millions of years of evolution, feathers were becoming more functional during the gliding, while feathers on the legs began to disappear. It has been a surprising fact for Archaeopteryx to have wings that are similar to the modern configurations. However, it is less so considering the long history of evolution from the early dinosaurs, when feathers had already been a crucial element in the survival of small-sized dinosaurs. With a close examination of the feathery wings of Archaeopteryx specimens, transitional features between dinosaurs and birds have been identified (Xv, 2012). Archaeopteryx is found to have multi-layered feathery wing structures, which differs from the single layered modern structures. Such a discovery indicates that the function of feathers in flying was not fully developed for Archaeopteryx, which makes a single layer of wings inadequate for flying. As the initial function of feathers was unrelated to flying, single feathers were still too weak to lift the Archaeopteryx while flying. It was only through further evolutions that the flying potential of feathers were maximized.

Tails are another important component in the evolution of birds. Through the observations of a dinosaur and a bird, the differences in the tails are obvious. The long and bulky tails of dinosaurs became the major obstacle for the lineage that evolved into birds. The modern tails of bird have further developed functionalities of attracting mates, communication between individuals through visual message, as well as safeguarding the relatives. Thus, the process of how the tails were transformed became the interest of many researchers. A study done by Rashid (2014) attempted to explain the process of how the reptilian theropod dinosaur bone in the long tail had evolved into the aerodynamically functional fan-shaped tail. the researchers assumed that the fused tails of early birds were the result of a combination of mutations, that occurred in a long period of time. However, there were not enough fossil records to support the hypothesis. No matter how long the tail of an animal is, a similar termination mechanism is applied in the embryo phases to ensure that tails do not grow longer without control. The similarity in this mechanism has made it possible for researchers to perform experiments on rat to study the mutation of tail genes for early birds (Rashid, 2014). From the observations of the genetic experiments on the lab rats, it has been found that a singular mutation on the genes that causes the tail truncations may not be adequately significant to be maintained, while mutation on multiple points would cause potential paralysis. Therefore, only those mutations that are between the two are more likely to prevail. Through the experiments, although no precise determinations on the scale and time of mutations for early birds was established, the hypothesis that mutations are indeed a more than probable cause for the transformation of the tails for early birds. The findings need to be further supported with more observations of different types of bird tails and fossil records.

From the analysis above, it can be concluded that body size reductions were the key to the explosive evolutions for early birds. Feathers used to be mistaken as the exclusive feature of birds, but were then found to be a functional part for dinosaurs millions of years before the flying functionalities were explored. Finally, the study by Rashid has revealed how people can explore the way evolution took place in ancient times with experiments that are independent from the fossil records. It has been confirmed that accumulation of mutations is indeed the most probable cause for the truncation in tails of early birds. It is wrong to assume that the bird species came into being from a sudden burst of mutation from the dinosaurs, but rather the accumulative mutations made the explosive evolution and diversifications of birds possible. It should be noted that the obtainment of the three features may not have occurred at the same period of time, but each of them are the determining factor for the formation of the bird species. There are also other features in the evolution processes, such as the formation of beaks, which can be further explored for its importance in the evolution.

References:

Ksepka, D. T. (2014). Evolution: A rapid flight towards birds. Current Biology: CB, 24(21), R1052-R1055. doi: 10.1016/j.cub.2014.09.018

Rashid, D. J., Chapman, S. C., Larsson, H. C., Organ, C. L., Bebin, A., Merzdorf, C. S., . . . Horner, J. R. (2014). From dinosaurs to birds: A tail of evolution. Evodevo, 5(1), 25-25. doi:10.1186/2041-9139-5-25

Xu, X. (2012). Evolution: Taking wing with weak feathers. Current Biology: CB, 22(23), R992. doi: 10.1016/j.cub.2012.10.015

Zhou, Z. (2014). Dinosaur evolution: Feathers up for selection. Current Biology: CB, 24(16), R751-R753. doi: 10.1016/j.cub.2014.07.017

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