For this essay’s purposes, the most important ecological understanding is that the Sun provides all of earthly life’s energy, either (all except nuclear-powered electric lights driving photosynthesis in greenhouses, as that energy came from dead stars). Today’s hydrocarbon energy that powers our industrial world comes from captured sunlight. Exciting electrons with photon energy, then stripping off electrons and protons and using their electric potential to power biochemical reactions, is what makes Earth’s ecosystems possible. Too little energy, and reactions will not happen (such as ice ages, enzyme poisoning, the darkness of night, food shortages, and lack of key nutrients that support biological reactions), and too much (such as , ionizing radiation, temperatures too high for enzyme activity), and life is damaged or destroyed. The journey of life on Earth has primarily been about adapting to varying energy conditions and finding levels where life can survive. For the many hypotheses about those ancient events and what really happened, the answers are always primarily in energy terms, such as how it was obtained, how it was preserved, and how it was used. For life scientists, that is always the framework, and they devote themselves to discovering how the energy game was played.
The Triassic began hot and ended hot, and the Jurassic and Cretaceous were also hot, so staying warm was not a significant issue for dinosaurs. stayed cool by becoming aquatic, and for land-based dinosaurs, features such as plates apparently replaced the sails of for both heating and cooling, and like the synapsid sail, those plates may have also been used for display. Also, like the cliché, many large herbivorous dinosaurs lived near cooling swamps, although the issue has been controversial. Cooling swamps and protective water holes that we see in the tropics today were a major aspect of Mesozoic landscapes. But the thermoregulatory aspect that most work is directed toward today is how dinosaurs kept warm. There is compelling evidence that dinosaurs regulated their body temperature in myriad ways, including internal chemistry. All bipedal animals today are endotherms and they all have four-chambered hearts, as dinosaurs did. , dinosaurs living near the poles (, ), and of dinosaur bones all support the idea that , but one of the more intriguing areas is that of . Like tree rings, bones have seasonal growth rings and they have been read for many dinosaur fossils. They have been used to determine dinosaurian life expectancies. could live to be about 30, giant could live to be 50, and smaller dinosaurs, as with smaller mammals, lived shorter lives. The tiny ones only lived three-to-four years and the mid-sized ones lived seven-to-fifteen years. Growth rates also provide thermoregulation evidence. Tyrannosaurs had juvenile growth spurts and largely stopped growing as adults, and sauropods had growth rates equivalent to today’s whales, which are Earth’s fastest growing animals. But there is also evidence of ectothermic dynamics. The great size of dinosaurs would have led to relatively easy ways to stay warm, as large animals have a greater mass-to-surface area ratio, like the way in which . Also, in the generally hot Mesozoic times, staying warm would have been fairly easy, particularly for huge dinosaurs.
PA School Prerequisites - The Physician Assistant Life - Essay
is complex, but the preceding presentation is largely adequate for this essay’s purpose, while it can be helpful to be aware that the physics behind FE and antigravity technologies will probably render the Standard Model obsolete. If FE, antigravity, and related technologies finally come in from the shadows, the elusive may come with them, and the Unified Field might well be consciousness, which will help unite the scientist and the mystic, and . But that understanding is not necessary to relate the story that White Science tells today of how Earth developed from its initial state to today’s, when complex life is under siege by an ape that quickly spread across the planet like a cancer once it achieved the requisite intelligence, social organization, and technological prowess.