Time When Ancestor First Appeared

Another important energy concept is efficiency. For the hunter-gatherers who cooked food over the campfire, the energy was used with an efficiency of less than 5% (the energy that benefited the user, such as cooking the food, warming the air, providing light, etc.). When humans began using hearths as they became more sedentary, their energy efficiency increased. As humans built dwellings and fireplaces, energy efficiency increased, and today, energy efficiency in advanced industrialized civilization reaches more than 35%. As humans kept increasing their gross energy input and the efficiency in using the energy, the . Just as , an increased energy surplus meant an easier life and a better chance of survival. In recent years, while the USA’s GDP-per-capita has risen, its energy-consumption-per-capita . Some have argued that it shows how much more efficient the USA’s economy has become, but it is more likely related to the USA’s de-industrialization, as heavy industry has moved to low-wage nations with weak environmental laws. The USA imports more finished goods in which the energy for mining and manufacturing them was used in other nations, like the imperial subsidy that the British received from their colonies, but far more pronounced when the USA is receiving finished industrial goods and not raw materials, as the British received from India. In generating energy, so-called technological societies have as advanced industrial ones, largely due to the .

When Did Photosynthesis Emerge on Earth? | Science

 (4) When an electron reduces P870+, it can now absorb another photon.

When did photosynthesis start? | Yahoo Answers

in the late Carboniferous. Arthropods became dominant predators once again, although cephalopods patrolled the reefs as apex predators. at that time, although the succeeding Devonian Period has been called the Golden Age of Brachiopods. As oxygen levels rose, trilobites lost segments and, hence, gill surface area, which may have been an ultimately extinctive gamble. When the Devonian extinction happened during anoxic events, trilobites steeply declined and thereafter only eked out an existence until the Permian extinction finally eliminated them from the fossil record. Fish began in the Silurian, which was a great evolutionary leap and arguably the most important innovation in vertebrate history. Jaws, tentacles, claws… features were advantageous, as animals could more effectively manipulate their environments and acquire energy. On land the colonization began, as mossy “forests” abounded, and made their appearance, although they were generally less than a hand-width tall when the Silurian ended, and nothing reached even waist-high.

Did photosynthesis begin 3.2 billion years ago? - YouTube

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.

27.08.2008 · When did oxygenic photosynthesis evolve

Two primary events drove the first phase of the Ordovician-Silurian mass extinction: the ice age caused the sea level to drop drastically and the oceans became colder. When sea levels fell at least 50 meters, the cooling shallow seas receded from continental shelves and eliminated entire biomes. Many millions of years of “easy living” in warm, shallow seas were abruptly halted. Several groups were ravaged, beginning with the plankton that formed the food chain’s base. About 50% of brachiopod and trilobite genera went extinct in the first phase, and cool-water species filled the newly vacant niches. Bivalves were largely found in seashore communities, were scourged when the seas retreated, and lost more than half of their genera. Nautiloids were also hit hard, and about 70% of reef and coral genera went extinct. The retreating seas somehow triggered the extinctions, and whether it was due to simply being exposed to the air or changing and cooling currents, nutrient dispersal patterns, ocean chemistry, and other dynamics is still debated, and those extinction events are being subjected to intensive research in the early 21st century.

When Did Life First Appear on Earth How did Life First Appear

What was most relevant to humans, however, was the almost-complete extinction during the Kellwasser event of the tetrapods that had come ashore. Tetrapods did not reappear in the fossil record until several million years after the Kellwasser event, and has even been referred to as the Fammenian Gap (the is the Devonian’s last age). The Kellwasser event also appeared to be a period of low atmospheric oxygen content, and some evidence is the lack of charcoal in fossil deposits. Recent research has demonstrated that getting wood to burn at oxygen levels of less than 13-15% may be impossible. Because all periods of complex land life show evidence of forest fires, it is today thought that oxygen levels have not dropped below 13-15% since the Devonian, but during the “charcoal gap” of the late Devonian, when the first landlubbing tetrapods went extinct, oxygen levels reached their lowest levels since the , which must have impacted the first animals trying to breathe air instead of water. During the , there is no charcoal evidence at all, which leads to the notion that oxygen levels may have even dropped below 13%. This drop may be related to severe climatic stresses on the new forests, which are probably related to the ice age that the forests helped bring about due to their carbon sequestering. That is an attractively explanatory scenario, but the continues. The first seed plants probably appeared before the Kellwasser event, but it was not until after the Fammenian Gap that seed plants began to proliferate.

When did Earth's oxygen atmosphere appear? - Bad Astronomy

Peter Ward led an effort to catalog the fossil record before and after Romer’s Gap, which found a dramatic that did not resume until about 340-330 mya. Romer’s Gap seems to have coincided with low-oxygen levels of the late Devonian and early Carboniferous. If coincided with a halt in colonization, just as the adaptation to breathing air was beginning, the obvious implication is that low oxygen levels hampered early land animals. Not just the lung had to evolve for the up-and-coming amphibians, but the entire chest cavity had to evolve to expand and contract while also allowing for a new mode of locomotion. When amphibians and splay-footed reptiles run, they cannot breathe, as their mechanics of locomotion prevent running and breathing at the same time. Even walking and breathing is generally difficult. This means that they cannot perform any endurance locomotion but have to move in short spurts. This is why today’s predatory amphibians and reptiles are ambush predators. They can only move in short bursts, and then have to stop, breathe, and recover their oxygen deficit. In short, they have no stamina. This limitation is called . The below image shows the evolutionary adaptations that led to overcoming Carrier's Constraint. Dinosaurs overcame it first, and it probably was related to their dominance and the extinction or marginalization of their competitors. (Source: Wikimedia Commons)