The Reign of Terror: Was it Justified - Sample Essays
But the branch of the that readers might find most interesting led to humans. Humans are in the phylum, and the last common ancestor that founded the Chordata phylum is still a mystery and understandably a source of controversy. Was our ancestor a ? A ? Peter Ward made the case, as have others for a long time, that it was the sea squirt, also called a tunicate, which in its larval stage resembles a fish. The nerve cord in most bilaterally symmetric animals runs below the belly, not above it, and a sea squirt that never grew up may have been our direct ancestor. Adult tunicates are also highly adapted to extracting oxygen from water, even too much so, with only about 10% of today’s available oxygen extracted in tunicate respiration. It may mean that tunicates adapted to low oxygen conditions early on. Ward’s respiration hypothesis, which makes the case that adapting to low oxygen conditions was an evolutionary spur for animals, will repeatedly reappear in this essay, as will . Ward’s hypothesis may be proven wrong or will not have the key influence that he attributes to it, but it also has plenty going for it. The idea that fluctuating oxygen levels impacted animal evolution has been gaining support in recent years, particularly in light of recent reconstructions of oxygen levels in the eon of complex life, called and , which have yielded broadly similar results, but their variances mean that much more work needs to be performed before on the can be done, if it ever can be. Ward’s basic hypotheses is that when oxygen levels are high, ecosystems are diverse and life is an easy proposition; when oxygen levels are low, animals adapted to high oxygen levels go extinct and the survivors are adapted to low oxygen with body plan changes, and their adaptations helped them dominate after the extinctions. The has a pretty wide range of potential error, particularly in the early years, and it also tracked atmospheric carbon dioxide levels. The challenges to the validity of a model based on data with such a wide range of error are understandable. But some broad trends are unmistakable, as it is with other models, some of which are generally declining carbon dioxide levels, some huge oxygen spikes, and the generally relationship between oxygen and carbon dioxide levels, which a geochemist would expect. The high carbon dioxide level during the Cambrian, of at least 4,000 PPM (the "RCO2" in the below graphic is a ratio of the calculated CO2 levels to today's levels), is what scientists think made the times so hot. (Permission: Peter Ward, June 2014)
What were three problems that faced the king in his reign?
Another energy-related activity probably appeared on a large scale during the reign of dinosaurs: . Although territoriality , , , , and today, it is most common among birds and mammals. Territoriality is primarily about preserving an animal’s energy base from competition, and it is usually a behavior oriented toward others of the same species, which would eat the same food resources and mate with the same potential partners. Just as what scientists call , territorial behavior may go all the way back to the . But the social behaviors apparent in dinosaurs probably also meant territorial behavior, and probably on a scale never experienced before on Earth. Even the suspected display function of implies territorial behavior. All are territorial, and human political units such as are little more than ape territoriality writ large, as peoples protect their energy and mating bases. In light of the (with its apotheosis in the peacock, although, as usual, ), and the phenomenon perhaps goes , along with the discovery of dinosaurian mass nesting sites, herd behaviors, and the like, many scientists believe that .
As smoke cleared and dust settled, literally, from the , the few surviving mammals and birds crept from their refuges, seeds and spores grew into plants, and the began, which is also called the Age of Mammals, as they have dominated this era. The Cenozoic’s first period is the , which ran from about 66 mya to 23 mya. As this essay enters the era of most interest to most humans, I will slice the timeline a little finer and use the concept of epochs. The Paleogene’s first epoch is called the (c. 66 to 56 mya).
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Earth’s volume is about one trillion cubic kilometers, its core is believed to be about 90% iron, and the rest is largely nickel. The is thought to be mostly oxygen and silicon, and the remainder is largely composed of the lighter alkali and alkaline earth metals, such as sodium, potassium, and calcium. Those mantle metals are primarily bound in oxides. The mantle makes up more than 80% of Earth’s volume. The crust also is almost solely comprised of oxides. Silicon dioxide (sand and glass are made from it) is the most prevalent compound and the crust is, by mass, nearly 75% oxygen and silicon (), and nearly all of the remainder is aluminum, iron, and those lighter and earth metals. All other elements combined amount to less than 2% of Earth’s crust. An accompanying presents the current estimates of the relative concentrations of Earth’s mass and atoms that are relevant to this essay.
Holy Terror: The Rise of the Order of Assassins | HistoryNet
In the Fertile Crescent today, the ruins of hundreds of early cities are in their self-made deserts, usually buried under the silt of the erosion of exposed forest soils. As the Mediterranean Sea’s periphery became civilized, the same pattern was repeated; forests became semi-deserts and early cities were buried under silt. Before the rise of civilization, a forest ran from Morocco to Afghanistan, and only about 10% of the forest that still existed as late as 2000 BCE still remains. Everyplace that civilization exists today has been dramatically deforested. Humanity has since agriculture began. The only partial exceptions are places such as Japan, but they regenerated their forests by importing wood from foreign forests. North America and Asia have been supplying Japan with wood for generations. As civilizations wiped themselves out with their rapaciousness, some people were aware enough to lament what was happening, but they were a small minority. Usually lost in the anthropocentric view was the awesome devastation inflicted on other life forms. was only a prelude. Razing a forest to burn the wood and raise crops destroyed an entire ecosystem for short-term human benefit and left behind a lifeless desert when the last crops were wrenched from depleted soils. In the final accounting, the damage meted out to Earth’s other species, not other humans, may be humanity’s greatest crime. Humanity is the greatest destructive force on Earth since the , and our great task of devastating Earth and her denizens may be .