Evolution of Dinosaurs to Modern Animals

Dinosaurs didnt spring suddenly into existence two hundred million years ago, huge, toothy, and hungry for grub. Like all living things, they evolved, slowly and gradually, according to the rules of Darwinian selection and adaptation, from previously existing creatures—in this case, a family of primitive reptiles known as archosaurs (ruling lizards). On the face of it, archosaurs werent all that different from the dinosaurs that succeeded them. However, these Triassic reptiles were much smaller than later dinosaurs, and they possessed certain characteristic features that set them apart from their more famous descendants (most notably, the lack of a locked-in posture for their front and hind limbs). Paleontologists may even have identified the single genus of archosaur from which all dinosaurs evolved: Lagosuchus (Greek for rabbit crocodile), a quick, tiny reptile that scurried across the forests of early Triassic South America, and that sometimes goes by the name Marasuchus. Evolution During the Triassic Period Confusing matters somewhat, the archosaurs of the middle to late Triassic period didnt only give rise to dinosaurs. Isolated populations of these ruling reptiles also spawned the very first pterosaurs and crocodiles. For as much as 20 million years, in fact, the part of the Pangean supercontinent corresponding to modern-day South America was thick with two-legged archosaurs, two-legged dinosaurs, and even two-legged crocodiles—and even  experienced paleontologists sometimes have trouble distinguishing between the fossil specimens of these three families! Experts are unsure whether the archosaurs from which the dinosaurs descended coexisted with the therapsids (mammal-like reptiles) of the late Permian period, or whether they appeared on the scene after the Permian/Triassic Extinction Event 250 million years ago, a geologic upheaval that killed about three-quarters of all land-dwelling animals on earth. From the perspective of dinosaur evolution, though, this may be a distinction without a difference. Whats clear is that dinosaurs gained the upper hand by the start of the Jurassic period.  (By the way, you may be surprised to learn that therapsids spawned the first mammals around the same time, the late Triassic period, as archosaurs spawned the first dinosaurs.) The First Dinosaurs Once you climb your way out of late Triassic South America, the path of dinosaur evolution comes into much sharper focus, as the very first dinosaurs slowly radiated into the sauropods, tyrannosaurs, and raptors we all know and love today. The best current candidate for the first true dinosaur is the South American Eoraptor, a nimble, two-legged meat-eater akin to the slightly later Coelophysis of North America. Eoraptor and its ilk survived by eating the smaller crocodiles, archosaurs, and proto-mammals of its lush forest environment, and may have hunted by night. The next important event in dinosaur evolution, after the appearance of Eoraptor, was the split between saurischian (lizard-hipped) and ornithischian (bird-hipped) dinosaurs, which transpired just before the start of the Jurassic period. The first ornithischian dinosaur (a good candidate is Pisanosaurus) was the direct descendant of the vast bulk of the plant-eating dinosaurs of the Mesozoic Era, including ceratopsians, hadrosaurs, and ornithopods. Saurischians, meanwhile, split into two main families: theropods (the meat-eating dinosaurs, including tyrannosaurs and raptors) and prosauropods (the slender, bipedal, plant-eating dinosaurs that later evolved into gigantic sauropods and titanosaurs). A good candidate for the first prosauropod, or sauropodomorph, is Panphagia, the name of which is Greek for eats everything. Ongoing Dinosaur Evolution Once these major dinosaur families were established, around the start of the Jurassic period, evolution continued to take its natural course. But according to recent research, the pace of dinosaur adaptation  slowed down drastically during the later Cretaceous period, when dinosaurs were more rigidly locked into existing families and their rates of speciation and diversification slowed. The corresponding lack of diversity may have made dinosaurs ripe pickings for the K/T Extinction Event  when a meteor impact decimated planetary food supplies. Ironically, just the way the Permian/Triassic Extinction Event paved the way for the rise of dinosaurs, the K/T Extinction cleared the way for the rise of mammals—which had existed alongside the dinosaurs all along, in small, quivering, mouse-like packages.

The Affordable Care Act ( Aca ) - 1440 Words

â€Å"We will be moving further away from humanity-based health care and more towards the patient as a commodity. This was not the way my father practiced—nor will I.† This quote, from a surgeon in Michigan, was only one of many quotes gathered by The Doctors Company, which is the largest insurer of physician and surgeon medical liability in the nation, when they asked over 5,100 doctors about their thoughts on different aspects of Health Care Reform. American health care reform is something that was nearly seventy-five years in the making; since Franklin D. Roosevelt, U.S. presidents have struggled to enact health care reform, and most failed (Health Affairs). In September of 2009, President Barrack Obama addressed Congress with his proposed solution, it was called The Affordable Care Act (ACA). In this Act, Obama attempted to address a need most every American desired: to keep health insurance companies accountable for their customers’ health by preventing the companies from dropping someone from their plan, or denying their policyholders health insurance coverage if they had a pre-existing medical condition. The ACA also implemented an individual mandate which required almost all U.S. citizens and legal residents of America to carry health insurance coverage, or they would be subject to a fine. Although President Obama was able to identify that there was a large percentage of uninsured Americans who were in good health, and there was a fair share of citizens who could noShow MoreRelatedThe Affordable Care Act ( Aca )956 Words   |  4 PagesAbsract++++++++++++++++++++++++++= The Affordable Care Act (ACA) (also known as â€Å"Obamacare†) is an historic piece of legislation that has had massive effect on healthcare in the United States. 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In contrast, the liberals supported the ACA and â€Å"pride themselves on the factRead MoreThe Affordable Care Act ( Aca )1668 Words   |  7 PagesOn March 23,2010 the Affordable Care Act (ACA), also known as Obamacare, was signed into law. This act aims to provide affordable health care coverage for all United States citizens. â€Å"The Affordable Care Act affirms the core principle that everybody should have some basic security when it comes to their health care.† (President Obama) It will provide insurance to more than thirty million people who have been previously uninsured, and will be achieved by expanding Medicaid and extending federal subsidiesRead MoreThe Affordable Care Act ( Aca )1349 Words   |  6 PagesIn 2010 the Affordable Care Act (ACA), also known as Obamacare, was signed into act to help reform healthcare in the United States. Before and after the act was effective, many people were concerned with how it would affect our country as a whole and on an individual basis. 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Despite its good intent, the ACA is not as perfect as it may appear. In this paper, I will list the main features of the Act, its pros and cons, and how it affects you as an individual and discuss the King vs. Burwell lawsuitRead MoreThe Affordable Care Act ( Aca )890 Words   |  4 PagesOn March 23, 2010, the Affordable Care Act which is an Obamacare, is the United States federal statute signed into law by President Barack Obama. The Affordable Care Act (ACA) experienced many challenges, debates, and objections until the Supreme Court rendered a final decision on individual mandate healthcare insurance to uphold the health care law on June 28, 2012. The mandate healthcare insurance for workers by employers’ obligation through a regulated marketplace of health maintenance organizations

Characteristics of Expository free essay sample

The type of organization used for Setting the Table was the informative process. An expository essay developed by the informative process is a how to essay. This essay was wrote in a step-by-step process giving information in order, describing how to set the table. Time Order was used as the type of organization in the essay A Soul as Free as the Air. This expository essay uses specific dates and chronological organization of information from one period to another. This type of organization arranges information according to date or specific time. o Why do you think each author chose that type of organization for his or her essay? In what ways does this organizational choice make the essay effective? I believe that the informative process was the best way to describe and deliver information in the essay Setting the Table. I believe that the time order organization process was chosen by the author because there was information that needed to be given from different times. We will write a custom essay sample on Characteristics of Expository or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page What effect might the author have achieved with another type of organization or another type of expository essay? I think either time order or informative process could have been used for either of the essays. Using the time order for Setting the Table would have worked just as well, telling the reader â€Å"First this† â€Å"Second that† ect. o In what ways are these expository essays alike? In what ways are they different? o Explain your answers. These essays are very similar. Both are giving of facts and information. However, they are different because one is telling â€Å"how to† do something, giving specific directions to properly set a table. The other is a time line of Lucy Stones life and accomplishments.