So far in this essay, mammals have received scant attention, but the mammals’ development before the Cenozoic is important for understanding their rise to dominance. The , called , first , about 260 mya, and they had key mammalian characteristics. Their jaws and teeth were markedly different from those of other reptiles; their teeth were specialized for more thorough chewing, which extracts more energy from food, and that was likely a key aspect of success more than 100 million years later. Cynodonts also developed a secondary palate so that they could chew and breathe at the same time, which was more energy efficient. Cynodonts eventually ceased the reptilian practice of continually growing and shedding teeth, and their specialized and precisely fitted teeth rarely changed. Mammals replace their teeth a . Along with tooth changes, jawbones changed roles. Fewer and stronger bones anchored the jaw, which allowed for stronger jaw musculature and led to the mammalian (clench your teeth and you can feel your masseter muscle). Bones previously anchoring the jaw were no longer needed and . The jaw’s rearrangement led to the most auspicious proto-mammalian development: . Mammals had relatively large brains from the very beginning and it was probably initially . Mammals are the only animals with a , which eventually led to human intelligence. As dinosaurian dominance drove mammals to the margins, where they lived underground and emerged to feed at night, mammals needed improved senses to survive, and auditory and olfactory senses heightened, as did the mammalian sense of touch. Increased processing of stimuli required a larger brain, and . In humans, only livers use more energy than brains. Cynodonts also had , which suggest that they were warm-blooded. Soon after the Permian extinction, a cynodont appeared that may have ; it was another respiratory innovation that served it well in those low-oxygen times, functioning like pump gills in aquatic environments.
For the first concept presented above, for conventional renewable energy sources, they are replenished by sunlight or radiation from Earth’s interior; one is fusion, and the other is fission. For so-called non-renewable energy sources, such as hydrocarbons and fissile materials, they are either renewed on timescales so vast that they are effectively non-renewable for humans (such as ), or are “renewed” by the (fissile materials), so could only be renewed with new planetary formation. In mainstream thought, the currently non-renewable energy resources are primarily hydrocarbons (petroleum, coal, and natural gas) and uranium. Much of the debate centers around the definition of oil. What has been called oil for the past 150 years is today called . It is the oil formed by the , and can be mined by drilling wells and extracting it with the conventional methods that have been used since the beginning, and new techniques are periodically invented to increase the rate and total extraction. For conventional oil, humanity has unearthed about 1.1 trillion barrels since 1859, and about as of 2014. Production of conventional oil peaked in 2006 at 25 billion barrels per year and has declined since then. At current production rates, conventional oil will be completely depleted in less than 50 years. About another five billion barrels per year are called unconventional oil, which is called heavy oil, extra heavy oil, and oil sands. Those unconventional oils comprise trillions more barrels, and total and arguably more. For fissile materials, primarily uranium, the peak may have already been reached by 2014, or it . For , in that the peak may have already been reached, or it is only a few decades into the future at most. For coal, may also be only a few decades into the future. Peak extraction usually occurs when about half of the recoverable energy resource has been mined. In summary, the energy resources that have powered the Industrial Revolution are all on their way to largely vanishing in this century. The only resources with seeming viability past this century are coal and unconventional oil, which brings us to the second concept: .
Is Humanity Suicidal Essay Examples | Kibin
Complex life means, by definition, that it has many parts and they move. Complex life needs energy to run its many moving parts. Complexity’s dependence on greater levels of energy use not only applies to all organisms and ecosystems, but it has also applied to all human civilizations, as will be explored later in this essay. When cells became “complex” with organelles, a tiny observer inside that cell would have witnessed a bewildering display of activity, as mitochondria sailed through the cells via “scaffolding” on their energy generating missions, the ingestion of molecules for fuel and to create structures, the miracle of cellular division, the constant building, repair, and dismantling of cellular structures, and the ejection of waste through the cellular membrane. The movement of molecules and organelles in eukaryotic cells is accomplished by using the same protein that became muscle: actin. Prokaryotes used an , and their provide their main mode of travel, to usually move toward food and safety or away from danger, including predators.