Introduction & Significance of Photosynthesis !

Carbon dioxide, on the other hand, has been generally decreasing as an atmospheric gas for billions of years, and has . The geochemical process is like nitrogen's in that atmospheric water combines with carbon dioxide to form a weak acid, which then falls to Earth in precipitation. But carbon is in the same elemental family as an abundant crustal element: . in crustal compounds and turns into in a process called . Most of Earth’s was probably removed by this process, although the exact mechanisms are in dispute. In all paleoclimate studies, carbon dioxide is a prominent variable, if not prominent variable, for determining Earth’s surface temperature. But perhaps as early as three bya, life became a significant source of carbon removal from the atmosphere, as life forms died and sank to the ocean floor, were subsequently buried by , and further buried them into Earth’s crust and mantle.

What is the importance of photosynthesis in an …

Oscillations in the photosynthetic Calvin cycle - examination of a mathematical model.

What is the significance of photosynthesis

Ornithischians started slowly and began to become common in the late Jurassic, just when the greatest biological innovation in the past 300 million years began: the appearance of , which first bloomed about 160 mya. Until that time, plant survival strategies included how to avoid being eaten by animals, whether it was bark, height, poisonous foliage, etc. Flowering plants adopted a different strategy by laying out a banquet for animals. The primary benefit for plants was , as well as attracting animals that did not seek to eat the plants and even ended up protecting them. The advantage for animals was an easily acquired and tasty meal. It was the greatest direct symbiosis between plants and animals ever, other than plants providing the oxygen that animals breathe, which is inadvertent. The two primary aspirations that seed plants achieve for successful reproduction are becoming fertilized via pollination and placing seeds where they can become viable offspring (and feces fertilizer could only help). Flowering plants, also called angiosperms, did not invent animal assistance from whole cloth. Some Jurassic insects have been found in association with (conifer) cones, and were probably doing the work that the wind previously performed. Like the , attracting animals to plants, to eat the pollen and nectar, was like a reproductive enzyme: animals carried the key to the lock to initiate reproduction. Other animals ate the fruit and thereby spread the seeds. That relationship did not become significant until the mid-Cretaceous. Angiosperms mature faster and produce more seeds than gymnosperms do. By the Cretaceous’s end, angiosperms dominated tropical biomes where ferns and cycads used to thrive, and they pushed conifers to the high latitudes, just as they have today. That tropical dominance is probably related to the insect population, which prefers warm climates. Angiosperms became Earth’s dominant plants after the and comprise more than 90% of plant species today.

What is photosynthesis, and how does it work?

When sea levels rise as dramatically as they did in the Cretaceous, coral reefs will be buried under rising waters and the ideal position, for both photosynthesis and oxygenation, is lost, and reefs can die, like burying a tree’s roots. About 125 mya, reefs made by , which thrived on , began to displace reefs made by stony corals. They may have prevailed because they could tolerate hot and saline waters better than stony corals could. About 116 mya, an , probably caused by volcanism, which temporarily halted rudist domination. But rudists flourished until the late Cretaceous, when they went extinct, perhaps due to changing climate, although there is also evidence that the rudists . Carbon dioxide levels steadily fell from the early Cretaceous until today, temperatures fell during the Cretaceous, and hot-climate organisms gradually became extinct during the Cretaceous. Around 93 mya, , perhaps caused by underwater volcanism, which again seems to have largely been confined to marine biomes. It was much more devastating than the previous one, and rudists were hit hard, although it was a more regional event. That event seems to have , and a family of . On land, , some of which seem to have , also went extinct. There had been a decline in sauropod and ornithischian diversity before that 93 mya extinction, but it subsequently rebounded. In the oceans, biomes beyond 60 degrees latitude were barely impacted, while those closer to the equator were devastated, which suggests that oceanic cooling was related. shows rising oxygen and declining carbon dioxide in the late Cretaceous, which reflected a general cooling trend that began in the mid-Cretaceous. Among the numerous hypotheses posited, late Cretaceous climate changes have been invoked for slowly driving dinosaurs to extinction, in the “they went out with a whimper, not a bang” scenario. However, it seems that dinosaurs did go out with a bang. A big one. Ammonoids seem to have been brought to the brink with nearly marine mass extinctions during their tenure on Earth, and it was no different with that late-Cretaceous extinction. Ammonoids recovered once again, and their lived in the late Cretaceous, but the end-Cretaceous extinction marked their final appearance as they went the way of and other iconic animals.

© 1958 Nature Publishing Group © 1958 ..

While oxygen level changes of the model show early fluctuations that the model does not, both models agree on a huge rise in oxygen levels in the late Devonian and Carboniferous, in tandem with collapsing carbon dioxide levels. There is also virtually universal agreement that that situation is due to rainforest development. Rainforests dominated the Carboniferous Period. If the Devonian could be considered terrestrial life’s , then the Carboniferous was its . In the Devonian, plants developed vascular systems, photosynthetic foliage, seeds, roots, and bark, and true forests first appeared. Those basics remain unchanged to this day, but in the Carboniferous there was great diversification within those body plans, and Carboniferous plants formed the foundation for the first complex land-based ecosystems. Ever since the episodes, there has , and the that have prominently shaped Earth’s eon of complex life probably always began with ice sheets at the South Pole, and the current ice age arguably is the only partial exception, but today’s cold period really began about 35 mya, .

In retrospect: Fifty years of C 4 ..

In the 19th century, the Jurassic was called the Golden Age of Dinosaurs, but that moniker is arguably most applicable to the late Cretaceous, and it was a golden age clear up until a bolide impact brought it all to an end. One of the uglier disputes in paleontology’s history was a bent on outcompeting each other in finding and describing dinosaur fossils. However, the dinosaur extinction is probably the largest and most contentious controversy in the history of paleontology. Again, the , due to Lyell’s and Darwin’s prevailing uniformitarianism, until my lifetime. The hypothesized bolide event, , was a kind of a bolide event inflicted on paleontology. Acrimonious disputes ignited that still burn, but it made studying mass extinctions respectable. Initially attacked and dismissed, the bolide impact hypothesis is by far today’s leading hypothesis for explaining the . However, at the same time, India was speeding toward its Asian destiny, and its movement is associated with . Also, , so the bolide event has some theoretical competition as a causative agent.

At the time, the significance of Hatch and ..

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.