What We Know About Dinosaur Life Spans

What We Know About Dinosaur Life Spans The bleached skeleton of a hundred-million-year-old Deinonychus can tell us a lot about what this dinosaur ate, how it ran, and even how it interacted with others of its kind, but not much about how long it lived before dropping dead of old age. The fact is, estimating the lifespan of the average sauropod or tyrannosaur involves drawing upon numerous strands of evidence, including analogies with modern reptiles, birds and mammals, theories about dinosaur growth and metabolism, and (preferably) direct analysis of the pertinent fossilized dinosaur bones. Before anything else, of course, it helps to determine the cause of death of any given dinosaur. Given the locations of certain fossils, paleontologists can often figure out if the unlucky individuals were buried by avalanches, drowned in floods, or smothered by sandstorms; also, the presence of bite marks in solid bone is a good indication that the dinosaur was killed by predators (though it’s also possible that the corpse was scavenged after the dinosaur had died of natural causes, or that the dinosaur had recovered from a previously inflicted injury). If a specimen can be conclusively identified as a juvenile, then death by old age is ruled out, though not death by disease (and we still know very little about the diseases that afflicted dinosaurs). Dinosaur Life Spans: Reasoning by Analogy Part of the reason researchers are so interested in dinosaur lifespans is that modern-day reptiles are some of the longest-lived animals on the earth: giant tortoises can live for over 150 years, and even crocodiles and alligators can survive well into their sixties and seventies. Even more tantalizingly, some species of birds, which are the direct descendants of dinosaurs, also have long lifespans. Swans and turkey buzzards can live for over 100 years, and small parrots often outlive their human owners. With the exception of humans, who can live for over 100 years, mammals post relatively undistinguished numbers, about 70 years for an elephant and  40 years for a chimpanzee, and the longest-lived fish and amphibians top out at 50 or 60 years. One shouldnt rush to conclude that just because some of the relatives and descendants of dinosaurs regularly hit the century mark, dinosaurs must have had long life spans as well. Part of the reason a giant tortoise can live so long is that it has an extremely slow metabolism; its a matter of debate whether all dinosaurs were equally cold-blooded. Also, with some important exceptions (such as parrots), smaller animals tend to have shorter lifespans, so the average 25-pound Velociraptor might have been lucky to live beyond a decade or so. Conversely, larger creatures tend to have longer lifespans, but just because a Diplodocus was 10 times bigger than an elephant doesn’t necessarily mean it lived ten times (or even twice) as long. Dinosaur Life Spans: Reasoning by Metabolism The metabolism of dinosaurs is still a matter of ongoing dispute, but lately, some paleontologists have advanced a convincing argument that the largest herbivores, including sauropods, titanosaurs, and hadrosaurs, achieved homeothermy, that is, they warmed up slowly in the sun and cooled down equally slowly at night, maintaining a near-constant internal temperature. Since homeothermy is consistent with a cold-blooded metabolism, and since a fully warm-blooded (in the modern sense) Apatosaurus would have cooked itself from the inside out like a giant potato, a lifespan of 300 years seems within the realm of possibility for these dinosaurs. What about smaller dinosaurs? Here the arguments are murkier, and complicated by the fact that even small, warm-blooded animals (like parrots) can have long life spans. Most experts believe that the life spans of smaller herbivorous and carnivorous dinosaurs were directly proportional to their size, for example, the chicken-sized Compsognathus might have lived for five or 10 years, while a much bigger Allosaurus might have topped out at 50 or 60 years. However, if it can be conclusively proved that any given dinosaur was warm-blooded, cold-blooded, or something in between, these estimates would be subject to change. Dinosaur Life Spans: Reasoning by Bone Growth You might think that an analysis of actual dinosaur bones would help clear up the issue of how fast dinosaurs grew and how long they lived, but frustratingly, this isnt the case. As the biologist, R.E.H. Reid writes in The Complete Dinosaur, [bone] growth was often continuous, as in mammals and birds, but sometimes periodic, as in reptiles, with some dinosaurs following both styles in different parts of their skeletons. Also, to establish rates of bone growth, paleontologists need access to multiple specimens of the same dinosaur, at different growth stages, which is often an impossibility given the vagaries of the fossil record. What it all boils down to is this: some dinosaurs, such as the duck-billed Hypacrosaurus, grew at phenomenal rates, reaching adult sizes of a few tons in a mere dozen or so years (presumably, this accelerated rate of growth reduced the juveniles window of vulnerability to predators). The trouble is, everything we know about cold-blooded metabolism is inconsistent with this pace of growth, which may well mean that Hypacrosaurus in particular (and large, herbivorous dinosaurs in general) had a type of warm-blooded metabolism, and thus maximum life spans well below the 300 years ventured above. By the same token, other dinosaurs seem to have grown more like crocodiles and less like mammals, at a slow and steady pace, without the accelerated curve seen during infancy and adolescence. Sarcosuchus, the 15-ton crocodile better known as the SuperCroc, probably took about 35 or 40 years to reach adult size, and then continued growing slowly for as long as it lived. If sauropods followed this pattern, that would point to a cold-blooded metabolism, and their estimated life spans would once again edge up toward the multiple-century mark. So what can we conclude? Clearly, until we establish more details about the metabolism and growth rates of various species, any serious estimates of dinosaur lifespans have to be taken with a gigantic grain of prehistoric salt!

The use of Sales Tax Essay Example | Topics and Well Written Essays - 750 words

The use of Sales Tax - Essay Example The drive of capitalism for this country relied on many factors that included slavery, turned raw goods into products, factories, and the ability to produce such a drastic workforce. Hence, Smith’s ideas of capitalism along with an adequate tax system that can power the nation in its quest to be financially solidified. The use of sales tax in America is implemented at a state level and is utilized for education, infrastructure, and Medicare. Many cities and countries have their own special rules regarding state tax. In essence, there is no federal sales tax. Clearly, that is because the population of state tax varies based on population, deficit, and economic growth (â€Å"Rousse, 66†).   Although no clear of sales tax can be found during the revolutionary time period, the forefathers of the country did implement an excise tax on whiskey enacted in 1791. For instance, Minnesota does not have a sales tax. Sales tax is calculated by multiplying the original price of the item by a tax rate. Sales tax is also special in a fact because it is collected at the time of sale (â€Å"Rousse, 66†).    Sales tax is unique in its manner because it is only imposed once during the time of purchase. However, this rule can be modified. For instance, items such as used cars fit this description. In this particular scenario, sales tax can be charged on the same item multiple times (â€Å"Rousse, 66†). The common example of sales tax is prevalent in grocery stores in which individuals are charged with this tax when buying their produce and groceries. Researchers that study economics have comprehensively studies the effects of sales tax have concluded that it harnesses the local economy. One of the key elements that sales tax is utilized for is to fund education. Since sales tax is based on a state basis. Illinois is a prime example of this sales as the school system is injected with sales tax revenue (â€Å"Rousse, 66†). This is essential beca use the money is allocated in a very efficient manner that benefits the economy. Since the housing market is on the bubble right now, the sales tax that is derived from the properties are valuable enough to dictate funding of education. As a matter of fact, lawmakers approved sales tax as a funding source for school districts in 2007. Since the market is on the bubble, many economists say that it makes logical sense to facilitate individuals by relying on sales tax rather than property tax. The debate over sales tax has been the hallmark of criticism and critique. Many individuals feel that the sales tax should be regressive just like the progressive tax. Many people insist that the sales tax imposes a huge burden on low-income families. In addition, the government is contemplating the decision to charge sales tax to online retailers. During the year of 1992, the Supreme Court ruled that retailers don't have to collect sales taxes in states where they do not possess any leverage (â €Å""Should States Require Online Retailers to Collect Sales Tax?† ). Both state and the local government has been urging Congress to repeal that decision and actually charge online retailers a sales tax as numerous bills have been proposed in Congress. Many Americans feel that shopping online is cost-effective as it allows them to skip this tax. In essence, if an individual bought items from an online retailer, they are obligated to owe tax to state even though the states really do not have supreme authority to

The Tragic Decline of BlackBerry Essay Example | Topics and Well Written Essays - 500 words

The Tragic Decline of BlackBerry - Essay Example This coupled with the modern design that it consistently infuses with the minor details that separates it from the rest. But the unsparing competition in its arena has made BlackBerry almost desperate in its attempts to take part of the viability of the market against other specialized and well-established counterparts. In its quest to take a cut and compete with other giants such as Apple, Sony Ericsson, Google and Microsoft, its maker Research in Motion is constantly in its feet testing the market and looking for a solid niche that goes beyond its comfortable smartphone sphere. It has endeavoured into other business ventures that have fallen quite short of the expectations and overall appeal. The release of the BlackBerry Playbook that claimed to topple down Apple’s Ipad was an epic failure the users and techies dismissed the product as being a major let down. Harry McCracken in his article â€Å"BlackBerry: Vision Needed† deemed it as being tremendously disappointing and this could be attributed to what Ben Bajarin in â€Å"The Tragic Decline of BlackBerry† refers to as lost customer interest. These two articles recognize the problems that BlackBerry is facing. There must be a deeper look into contemplating first what products will identify with BlackBerry instead of merely releasing new ones for the sake of market share. McCracken unwittingly said that it is a good move for the company not to announce any new product at DevCon in San Francisco in contrast to what it did it 2010 that built the hype for Playbook. Instead, it is focusing on the new operating system called BBX. Bajarin is on the same page by saying that RIM’s attempt to partake of all the glamor fails to impress the actual customers who make use of the product. These types of exposure are all but the personality of Steve Jobs and the characteristic of Apple. BlackBerry need not get in on the mix and instead stick to what it does best.