Mass extinction events can seem quite capricious as to what species live or die. generally outcompeted their ancestral for hundreds of millions of years. Ammonoids were lightweight versions of nautiloids, and they often thrived in shallow waters while nautiloids were banished to deep waters. Both dwindled over time, as they were outcompeted by new kinds of marine denizens. In the and mass extinctions, deep-water animals generally suffered more than surface dwellers did, but the nautiloids’ superior respiration system still saw them survive. Also, nautiloids laid relatively few eggs that took about a year to hatch, while ammonoids laid more eggs that hatched faster. However, the asteroid-induced Cretaceous mass extinction annihilated nearly all surface life while the deep-water animals fared better, and nautiloid embryos that rode out the storm in their eggs were survivors. The Cretaceous extinction while and comprise another group of living fossils, although that status is disputed in 2014. was about the only land animal of significance that survived the Permian extinction and it dominated the early Triassic landmass as no animal ever has. It comprised about 95% of all land animals. Why , which was like a reptilian sheep? Nobody , but it may have been the luck of the draw. Perhaps relatively few bedraggled individuals existed in some survival enclave until the catastrophe was finished, and then they quickly bred unimpeded until , for the most spectacular species radiation of all time, at least until humans arrived on the evolutionary scene.
There is also evidence that life itself can contribute to mass extinctions. When the eventually , organisms that could not survive or thrive around oxygen (called ) . When anoxic conditions appeared, particularly when existed, the anaerobes could abound once again, and when thrived, usually arising from ocean sediments, they . Since the ocean floor had already become anoxic, the seafloor was already a dead zone, so little harm was done there. The hydrogen sulfide became lethal when it rose in the and killed off surface life and then wafted into the air and near shore. But the greatest harm to life may have been inflicted when hydrogen sulfide eventually , which could have been the final blow to an already stressed ecosphere. That may seem a fanciful scenario, but there is evidence for it. There is fossil evidence of during the Permian extinction, as well as photosynthesizing anaerobic bacteria ( and ), which could have only thrived in sulfide-rich anoxic surface waters. Peter Ward made this key evidence for his , and he has implicated hydrogen sulfide events in most major mass extinctions. An important aspect of Ward’s Medea hypothesis work is that about 1,000 PPM of carbon dioxide in the atmosphere, which might be reached in this century if we keep burning fossil fuels, may artificially induce Canfield Oceans and result in . Those are not wild-eyed doomsday speculations, but logical outcomes of current trends and , proposed by leading scientists. Hundreds of already exist on Earth, which are primarily manmade. Even if those events are “only” 10% likely to happen in the next century, that we are flirting with them at all should make us shudder, for a few reasons, one of which is the awesome damage that it would inflict on the biosphere, including humanity, and another is that it is entirely preventable with the use of technologies .
Mass extinction events may be the result of multiple ecosystem stresses that reach the level where the ecosystem unravels. Other than the meteor impact that destroyed the dinosaurs, the rest of the mass extinctions seem to have multiple contributing causes, and each one ultimately had an energy impact on life processes. The processes can be complex and scientists are only beginning to understand them. This essay will survey mass extinction events and their aftermaths in some detail, as they were critical junctures in the journey of life on Earth.
In light of all those paths that have led to nowhere, why do I think that my attempt will not be another dead end? It could well be, but it is at least a new route and it should be harmless, which I highly value; I have seen enough carnage in this lifetime and do not want to be responsible for any more .
It talks about the life of British soldiers in trenches.
Several years before writing this essay, as I began studying for this essay in earnest, I happened upon a , believe it or not, which helped me crystallize this essay’s epochal approach. The was missing from the author’s account, as well as the , of course, but in a discussion of socio-technical development, the author listed four different “vectors” of technological development, which he described as: Discovery, Invention, Innovation, and Diffusion. They corresponded to scientific discoveries, creating inventions, marketing them, and people using them. I have witnessed organized suppression in each vector.
[tags: Spiritual Journeys, Religion, Christianity, Jews]
Few dates before 1 CE will be used beyond this point in this essay, so for the remainder of this essay, unless "BCE" is applied to them, all dates will be CE dates, with “CE” dropped from them.
[tags: my nursing journey, My Philosophy of Nursing ]
I earlier compared people from different epochs. That stone tool Tesla what his/her invention would lead to a half-million years later, and members of the founding group could not have comprehended . Imagine a hunter-gatherer of 10 kya being dropped into Rome in 100 CE or London in 1500 CE. History has some relevant examples. When , about the last of his people, came out of hiding in his dying world and strode into civilization, it caused a sensation. He soon died of tuberculosis, but his encounters with civilization were recorded. He attended an opera, and the popular account portrayed his rapport with the diva, but Ishi actually stared in amazement at the , as he had never before seen so many people in one place. When he saw an airplane in flight, he laughed in amazement. Imagine a hunter-gatherer of 10 kya being dropped into imperial Rome. That hunter-gatherer had probably seen dogs, but horses, cows, sheep, and the like would have been astounding, and watching a horse or ox pull a cart would have been stunning. Crops would have been an amazing sight. Imagine that hunter-gatherer at the . The building and crowd alone would have boggled his mind, even if the festivities might have been horrifically familiar. Metals and glass would have seemed magical. Writing had not yet been invented in that hunter-gatherer’s world, so even the concept would have been difficult. Imagine him trying to learn math. There were no more singing and dancing religious rituals, and no wide-open spaces to hunt a meal. Imagine that hunter-gatherer visiting a Roman bath. Hot water alone would have been surreal, while the cavorting might have been delightful. What would his reaction have been to Rome’s markets? Rome was also loud and could be hellish, so the hunter-gatherer might have longed to flee to the countryside before long, but the countryside would have little resembled the one he knew. He obviously would not have understood anything that anybody said, but they were also all members of , so he would have seen many behaviors and traits that he eventually understood. But how long would his shock have lasted? Could he have really ever adapted to Roman society (if he did not quickly end up on the arena’s stage as a novelty)? Another surprise for that hunter-gatherer would be seeing people interact who did not know each other. People were interacting with members and not trying to kill them on sight, which became standard behavior in most hunter-gatherer societies that battled over territory (their food supply). Civilized life was all made possible by the local and stable energy source that agriculture provided, which led to an epoch that changed very little until the next energy source was tapped: the hydrocarbon energy that powered the Industrial Revolution. The next chapter will survey the developments that led to that momentous event. It is the only Epochal Event with historical documentation that showed how it developed, which is easier to reconstruct than examining stones and bones.