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All of these animals are endangered.
appeared in the Mesozoic and required oxygen to form calcium carbonate. They became so abundant in the high oxygen of the late Cretaceous that the rain of their bodies on ocean floors gave the its name: chalk (the Latin name). Calcium carbonate, the primary constituent of limestone, comes in two forms: and . The magnesium content in the oceans, as well as the ocean temperature, determines which form of calcium carbonate will dominate. The also marked the end of a 100-million-year ice age and gave way to about 200 million years of hot times. During , Earth has . That pattern also seems . Hot seas are generally and cold seas are usually . Calcite seas create , which influence the biome that forms. The and periods had vast carbonate hardgrounds, which disappeared during the and returned in the Greenhouse Earth age of dinosaurs, becoming common in the Jurassic. Today’s Icehouse Earth has aragonite seas, so organisms that form calcium carbonate shells use aragonite, which is less stable than calcite and its formation is sensitive to temperature and acidity. Coral reefs, key phytoplankton (which help produce Earth’s oxygen), and shellfish use aragonite today to form their shells. There is already that acidification of the oceans due to humanity’s burning of fossil hydrocarbon deposits to power the industrial age is interfering with the ability of coral, carbonate-forming phytoplankton, and shellfish to form their shells. That is only one of the industrial age’s many deleterious ecosystem impacts. The current aragonite-formation situation is not a theoretical construct of fearful environmentalists, but is a .
A mass extinction began when humans left Africa and with ancestors of , but it accelerated when that founder group of behaviorally modern humans . They quickly drove the , as well as the and . Once the inhabitable continents were filled with that founder group’s descendants, , humans independently domesticated plants and animals. The mass extinction continued with the Domestication Revolution, but in less spectacular fashion, usually via habitat destruction. The increasing density of human populations became the primary factor in driving other species to extinction, which were often local extinctions. Ancient and particularly drove north-African megafauna to extinction, but there were few other notable mass extinctions until . When they did, the greatest proportional demographic catastrophes since the extinction of all other human species began. Those same three continents earlier robbed of their megafauna were quickly shorn of their human populations, who were and and in the Americas. In the midst of that unprecedented disaster for , . Although industrialization raised the human standard of living as never before, as the energy of hydrocarbon fuels was exploited on a large scale for the first time, it also enabled greater environmental devastation. Humanity has been turning forests into deserts since the first civilizations (, , , , , , , , , ), and the only reason it has not gotten worse during the industrial era, at least in industrialized, nations, is because hydrocarbons instead of wood were burned. The extinction of the , in the midst of , were indicative of the vast damage that industrialized peoples could inflict on Earth’s ecosystems. Industrialization also accelerated Europe’s conquest of the world. It conquered and subjugated and peoples, reducing them to effective slavery and further devastating the ecosystems.
Warm-climate species migrate or go extinct.
Ice ages are an important realm of scientific investigation. Humanity’s colossal burning of Earth’s hydrocarbon deposits may well be delaying the ice sheets' return; they have been advancing and retreating in rhythmic fashion for . Today, the current pattern's accepted tipping point has been Earth’s orientation toward the Sun, particularly the , which has a roughly 100,000-year cycle. Although Earth’s orientation is universally considered to be the tipping point variable, it is not the only influence. The ultimate cause has been . about 35 mya due to its position near the South Pole and declining carbon dioxide levels. The current ice age began 2.5 mya and was likely initiated by the , which separated the Atlantic and Pacific oceans and radically altered oceanic currents. Also, . Those factors all contributed to the current ice age.
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.
List of Critically Endangered Animals
Another evolutionary concept is that all changes had mechanical reasons for happening (again, today’s science has ), and each mechanical change required some purpose in improving an organism’s chances of surviving to reproduce, or at least not have unduly impaired it. As evolution progressed, for each species, it was like taking a road, and the farther down the road a species went in its development, the “lifestyle” opportunities that its biological operation created precluded other kinds of styles. For instance, trees will never become . Trees went down the path of roots, , growing taller than their neighbors, and the like. A plant cannot choose locomotion as a way of life. It does not generate enough energy for it, for one thing. Animals went down a very different evolutionary path than plants did, and muscles, brains, livers, and the like have no analogy in plants and, by themselves, plants will not grow muscles or brains anytime soon, although humans have been making radical changes in animals over brief periods of time, such as the many breeds of dog.
Around when Harland first proposed a global ice age, a climate model developed by Russian climatologist concluded that if a Snowball Earth really happened, the runaway positive feedbacks would ensure that the planet would never thaw and become a permanent block of ice. For the next generation, that climate model made a Snowball Earth scenario seem impossible. In 1992, a professor, , that coined the term Snowball Earth. Kirschvink sketched a scenario in which the supercontinent near the equator reflected sunlight, as compared to tropical oceans that absorb it. Once the global temperature decline due to reflected sunlight began to grow polar ice, the ice would reflect even more sunlight and Earth’s surface would become even cooler. This could produce a runaway effect in which the ice sheets grew into the tropics and buried the supercontinent in ice. Kirschvink also proposed that the situation could become unstable. As the sea ice crept toward the equator, it would kill off all photosynthetic life and a buried supercontinent would no longer engage in . Those were two key ways that carbon was removed from the atmosphere in the day's , especially before the rise of land plants. Volcanism would have been the main way that carbon dioxide was introduced to the atmosphere (animal respiration also releases carbon dioxide, but this was before the eon of animals), and with two key dynamics for removing it suppressed by the ice, carbon dioxide would have increased in the atmosphere. The resultant greenhouse effect would have eventually melted the ice and runaway effects would have quickly turned Earth from an icehouse into a greenhouse. Kirschvink proposed the idea that Earth could vacillate between states.
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Extinction of animals essay | Holiday Philippines Blog
About 183 mya, linked to and events hit ammonoids hard, as usual. The extinction seems to have been confined to the oceans. Along with the appearance of , reefs slowly recovered in the Jurassic, and by the Jurassic’s end, lined Tethyan shores. Low-oxygen tolerating marine animals proliferated in the Jurassic. Ammonoids, with , developed large, thin-shelled varieties that housed the large gills probably required to navigate the Jurassic’s low-oxygen waters. Also, a different kind of cephalopod, , became plentiful in the Jurassic. The first appeared in the Jurassic, and they also developed a superior respiration system; they put their gills within their armor and developed a pump gill. As most seashore visitors know, crabs are quite tolerant of exposure to air, much as nautiloids suffer no ill effects when exposed to air for a short time. Crabs proliferated with the late Jurassic’s reefs, to (called the Tithonian event, or end-Jurassic extinction), which was caused by a sudden drop in sea levels, and the extinction again appeared to be largely restricted to marine biomes. On land, there were extinctions of , , and .
Essay about Animal Extinction - 3001 Words
According to , oxygen levels rose in the Cretaceous and reached nearly modern levels by the end. But anoxic events also dotted the Cretaceous, probably related to rising sea levels. The lived in the Cretaceous and reached three meters in length. It was a deep-water species that probably formed symbiotic relationships with chemosynthetic organisms, along with those other low-oxygen Mesozoic bivalves, and it went extinct as oxygen levels rose in the atmosphere and probably also in the seas.
Introduction: Endangered Species | New Scientist
Because of the stupendous energy demands of flight, birds not only have the superior air sac system for breathing, but their , the cell’s energy-generation centers, are far more efficient than mammalian mitochondria. Parrots in captivity can , scientists have noted an , and scientists may discover that wild albatrosses live to be 100 or more, when their tagging programs get that old. The may explain bird longevity, as the efficient mitochondria of birds . The theory is controversial and will be for many years, but I think that an engine analogy can help. A bird is a piece of high-performance biological technology, and when operating at peak output it puts all land-bound animals to shame. But a bird’s metabolism is usually in its slack state, only maximized during flight. Simply put, a bird has a great energy capacity that is rarely used to its fullest. It is like a high-performance engine that rarely runs near its . Such engines will last far longer than those regularly running near redline. High-performance technology that usually “loafs” in its slack state and is rarely taxed is expensive and long-lasting. The increased investment in superior technology allows for high performance and long life. High-quality technology is more economical in the long run, if the initial investment can be afforded.
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