With the paucity of fossils, particularly between 2.5 and 1.0 mya, a timeframe in which the bones of only about 50 individuals have been found so far, discoveries are regularly announced that can be promoted as finds that will . That recently discovered better suited for tool-making, in parallel to developing humans, and perhaps is even a human ancestor, which would relegate to an extinct offshoot, not a human ancestor. With such a scanty existing record, such announcements can be more than hyperbole. There are often heated controversies over the dates of fossils and artifacts, in which changing a date can radically alter how the evidence is viewed. Many findings can change from minor curiosity to paradigm-shifting discovery and back again, depending on the dates assigned to them.
During that “,” , , and the rise of grazing and predation had eonic significance. While many critical events in life’s history were unique, one that is not is multicellularity, , and some prokaryotes have multicellular structures, some even with specialized organisms forming colonies. There are , but the primary advantage was size, which would become important in the coming eon of complex life. The rise of complex life might have happened faster than the billion years or so after the basic foundation was set (the complex cell, oxygenic photosynthesis), but geophysical and geochemical processes had their impacts. Perhaps most importantly, the oceans probably did not get oxygenated until just before complex life appeared, as they were sulfidic from 1.8 bya to 700 mya. Atmospheric oxygen is currently thought to have remained at only a few percent at most until about 850 mya, although there are recent arguments that it remained low until only about 420 mya, when large animals began to appear and animals began to colonize land. Just as the atmospheric oxygen content began to rise, then came the biggest ice age in Earth’s history, which probably played a major role in the rise of complex life.
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It can be helpful at this juncture to grasp the cumulative impact of , inventing , inventing , inventing that made possible, and inventing . Pound-for-pound, the complex organisms that began to dominate Earth’s ecosphere during the Cambrian Period consumed energy about 100,000 times as fast as the Sun produced it. Life on Earth is an incredibly energy-intensive phenomenon, powered by sunlight. In the end, only so much sunlight reaches Earth, and it has always been life’s primary limiting variable. Photosynthesis became more efficient, aerobic respiration was an order-of-magnitude leap in energy efficiency, the oxygenation of the atmosphere and oceans allowed animals to colonize land and ocean sediments and even fly, and life’s colonization of land allowed for a . Life could exploit new niches and even help create them, but the key innovations and pioneering were achieved long ago. If humanity attains the , new niches will arise, even of the , but all other creatures living on Earth have constraints, primarily energy constraints, which produce very real limits. Life on Earth has largely been a for several hundred million years, but the Cambrian Explosion was one of those halcyonic times when animal life had its greatest expansion, not built on the bones of a mass extinction so much as blazing new trails.
Photosynthesis is a chemical ..
Really amazing are the innovative ways solar power is put into use. Now a team of scientists working in Sandia National Laboratories is focusing on exploring basic steps to
WSU researchers genetically alter rice plants – The …
Supply-side pests reduce the photosynthetic rate by attacking root, leaves and stem in a manner that reduces the photosynthetic rate. Important supply-side pests are defoliators, sapsuckers, spidermites, nematodes, diseases, and others. Defoliation attacks leaves and may cause wound healing losses, but the effects on yield depend on the age of leaves attacked, the loss rate, and compensation due to increased light penetration. In contrast, spidermites kill leaf cells, reducing photosynthesis in damaged leaves that are not shed, reducing light penetration to lower leaves. Stem borers and vascular plant diseases may slow the photosynthetic rate by reducing the translocation of water and nutrients, and some may kill whole plants. Thrips and armyworms may damage the terminal, inducing developmental delays and reducing yield.
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Photosynthesis is the process by which plants, using energy from sunlight, convert carbon dioxide and water into high energy fuels. It is responsible for all the fuel that feeds forest fires, and for the rapid grow-back of fuel after a fire. But even with the hundreds of millions of tons of coal and the billions of barrels of oil and gasoline that are burned annually, the carbon dioxide content of the atmosphere remains about .04%.