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DNA damage theory of aging - Wikipedia
Anasazi civilization also overtaxed its environment and collapsed in a drought, as did the . The lauding of Native American environmental conscience seems largely a romantic invention, like the “” fantasy. Although Native Americans obviously had a far gentler tenure on the land than what happened in the Old World, it may have been only a matter of time before they “progressed” with metal smelting, rampant deforestation, and the like. Without draft animals (bison were probably the only candidate for that, and turning them into domesticated draft animals may not have been feasible), their civilizations might have taken very different paths than the Old World’s. What kinds of civilizations might have emerged from the Western Hemisphere had Europe not intervened will always remain a tantalizing question, but we will never know; those civilizations show different ways to do it, even if what the Spaniards stumbled into seemed familiar, with cities, markets, elites, monumental architecture, warriors, priests, peasants, slaves, and so on.
Some scientists treat every proboscidean extinction as a unique mystery, unrelated to other proboscidean extinctions, and climate and resulting vegetation changes are hypothesized as agents of extinction (or other causes invoked), when the most probable cause stares at them each morning in the mirror. The devil in the details, but regarding the megafauna extinctions, some specialists cannot seem to discern a very clear pattern. Scientists, because they are human, have an inherent conflict of interest when attributing such catastrophes to non-human causes. During the remainder of this essay, it will become evident that there is a human penchant for absolving one’s in-group of responsibility for catastrophes and crimes committed against the out-group, and , scientists, and other professionals regularly engage in such interest-conflicted acts, whether they were defending their species, race, gender, nation, class, ideology, ethnicity, or profession. That in-group/out-group difference in treatment has a long history and probably goes back to the beginnings of territorial social animals.
How does DNA decay? • r/askscience - reddit
Kirschvink noted that reappeared in the geological record during the possible Snowball Earth times, after vanishing about a billion years earlier. Kirschvink noted that iron cannot increase to levels where they would create BIFs if the global ocean was oxygenated. Kirschvink proposed that the sea ice not only killed the photosynthesizers, but it also separated the ocean from the atmosphere so that the global ocean became anoxic. Iron from volcanoes on the ocean floor would build up in solution during the , and during the greenhouse phase the oceans would become oxygenated and the iron would fall out in BIFs. Other geological evidence for the vacillating icehouse and greenhouse conditions was the formation of cap carbonates over the glacial till. It was a global phenomenon; wherever the Snowball Earth till was, cap carbonates were atop them. In geological circles, deposited during the past 100 million years are considered to be of tropical origin, so scientists think that the cap carbonates reflected a tropical environment. The fact of cap carbonates atop glacial till is one of the strongest pieces of evidence for the Snowball Earth hypothesis. Kirschvink finished his paper by noting that the eon of complex life came on the heels of the Snowball Earth, and scouring the oceans of life would have presented virgin oceans for the rapid spread of life in the greenhouse periods, and this could have initiated the evolutionary novelty that led to complex life.
When investigating how ice ages begin and end, and feedbacks are considered. A positive feedback will accentuate a dynamic and a negative feedback will mute it. In the 1970s, and the author of today’s , , , which posits that Earth has provided feedbacks that maintain environmental . Under that hypothesis, environmental variables such as atmospheric and levels, levels, and Earth’s surface temperature have been kept relatively constant by a combination of geophysical, geochemical, and life processes, which have maintained Earth’s inhabitability. The homeostatic dynamics were mainly negative feedbacks. If positive feedbacks dominate, then “runaway” conditions happen. In astrophysics, are responsible for a wide range of phenomena. A runaway greenhouse effect may be responsible for . Climate scientists today are concerned that burning the hydrocarbons that fuel the industrial age . Mass extinctions are the result of Earth's becoming largely uninhabitable by the organisms existing during the extinction event. The ecosystems then collapse Mass extinction specialist recently proposed his as a direct challenge to the Gaia hypothesis.
Read in another language; DNA The structure of the DNA double helix
There was a “” in the early Triassic, and depending on the framework and which scientist is asked, it took Earth’s ecosystems (when the environment recovered enough to sustain normal ecosystems), (when terrestrial ecosystem diversity recovered), or (when marine ecosystem diversity recovered) to recover from the Permian extinction. On land, the forests slowly recovered, and dominated the early Triassic. dominated the Southern Hemisphere, and palm-tree-resembling and ginkgo trees (which first appeared in the late Permian, of which the living fossil is the only surviving member) also prospered. In the , on what became North America, Europe, and Siberia, conifer forests recovered and blanketed the land.
As scientists know with mammals, although , it comes with a great energetic cost. As with plants, an animal can spend its on consumption (metabolism) or investment (growth). An intriguing hypothesis is that growing large was part of an energy strategy, as the benefits of size (reduced risk of predation, ease of conserving body heat and consequently less need for a high metabolism, ability to access new food sources, such as foliage high above the ground) outweighed their costs (energy devoted to growth instead of metabolism, the need to constantly feed). Their size and the warm climate meant that large dinosaurs did not need as intense internal energy generation as mammals do, for instance, and dinosaurs may have been , with internal energy regulation greater than , but not as great as (mammals and birds).
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Oct 01, 2015 · DNA as a programming language
Also, the formation of Pangaea ( regarding what processes ) may have led to the dynamics that broke it apart. The Hawaiian Islands are that began forming more than 80 mya, and is due to a hotspot bubbling up from Earth’s mantle. Although the is , a prominent hypothesis is that the formation of Pangaea plugged hotspots and prevented heat from venting from Earth’s core, which led to a swelling and fracturing Pangaea. Part of the evidence for that hypothesis was relatively sudden and widespread volcanism sprouting up around Pangaea, which followed a known fracture pattern around such crustal upwellings. The volcanism and resultant fracture lines formed today’s continents. As can be seen in the during the late Permian, what became China and Siberia were on the northeast margins of Pangaea, bordering the Paleo-Tethys Ocean, and two volcanic events arising from China and Siberia are currently favored as key proximate causes of the Permian extinctions.
Not a very good programming language
After as little as a half-million years of bedraggled survivors adapting to ice age seas, the ice sheets retreated and the oceans rose. The of the time may have also changed, and upwelling, anoxia, and other dramatic chemistry and nutrient changes happened. Those dynamics are suspected to be responsible for the second wave of extinctions. There also seem to have been .Atmospheric oxygen levels may have fallen from around 20% to 15% during the Ordovician, which would have contributed to the mass death. Seafloor anoxia seems to have been particularly lethal to continental-shelf biomes, possibly all the way to shore. It took the ecosystems millions of years to recover from the Ordovician-Silurian mass extinction, but basic ecosystem functioning was not significantly altered in the aftermath, which is why a has been proposed as a more significant extinction event. The were laid down by the . Most oil deposits were formed in the era of dinosaurs and the processes of oil deposit formation were similar; they were related to oceanic currents. When currents came to shore via the bottom and the prevailing winds blew the top waters offshore, it became a and anoxic sediments could form. When the winds blew onshore and left via the bottom, the waters became clear and are known as nutrient deserts. The oscillation between nutrient traps and nutrient deserts can be seen in oil deposit sediments. In the mid-20th century, Soviet scientists revived an old hypothesis that oil was , a variation of which was also championed by , but improving tools and investigation invalidated those hypotheses. No petroleum geologists today seriously consider the abiogenic origin of hydrocarbons. Oil sediment formation events seem related to mantle and crust processes that created high sea levels and anoxic events, and the last great one was in the , which formed more than 10% of the world's oil deposits.
Every human generation contains, on average, about 60 mutations
Sauropods seem to have . Until relatively recently, animals as agents of ecosystem change and maintenance was a marginal idea. But today, is thought to be a seminal geophysical event in the Cambrian, and those huge sauropods probably had an ecosystem impact like what elephants have today in Africa. Elephants today break up woods as they feed, as they knock over trees and uproot them. That damage transforms the biome and provides opportunities for other kinds of herbivores and their predators. Elephants also and are considered , which have an outsized impact on their environment. Today, there is a “” to the overkill hypothesis regarding megafauna extinctions soon after humans appeared; such people minimize the impact of humans (their position has an inherent conflict of interest, as those ) and attribute the extinction of elephants of the Western Hemisphere (, ) to climate change and resulting changes in vegetation. If the current situation with African elephants is relevant, it is likelier that those vegetation changes were a of elephant extinction, not a cause. Elephant extinctions would have affected many other kinds of plants and animals, and could have precipitated . Similarly, those huge sauropods would not just have nibbled at vegetation and been relatively harmless browsers, but their vast bulk would have been ideal for pushing over trees to get at their foliage and other devastations of trees in particular, which would have dramatically impacted biomes. Giant dinosaurs probably had keystone species impacts on their environments, particularly the vegetation. Dinosaurs were not the only huge organisms in those days. The appeared in the Jurassic, and would have been immune to dinosaur browsing when they grew large enough. Below is an artist's conception of a typical Jurassic landscape (just as an allosaur and stegosaur are about to cordially interact). (Source: Wikimedia Commons)
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