When Did Photosynthesis Emerge on Earth? | Science
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.