In the Cambrian period, 500 million years ago, the seas were dominated by the armored group. Soft animals secrete metallic paste bodies that harden into protective shells of immense strength and deco beauty, some in the shape of rams’ heads or eagles’ wings, others like champagne flutes studded with dagger-sharp spines.
But by the Devonian period, about 70 million years later, most of the leggy theropods, briopods, well-shelled sailors, victims of robbery and their expensive ways were extinct.
as researchers Recently suggested In the journal Trends in Ecology and Evolution, the collapse of the Brachiopod empire exemplifies the conflict that defined life from the start: the search for phosphorous. Scientists have long known that the element phosphorous is essential on several fronts, and here it binds the DNA molecule together, powering every movement of the cell. The new report underscores another way that phosphate – the chemically useful form of phosphorous – has shaped the course of evolution as the arbiter of nature’s hard parts, its shells, teeth and bones.
“The phosphorous was stolen by vertebrates and bony fish,” said Peter Kraft, a paleontologist at Charles University in the Czech Republic and author of the new report. “Once that happened, they quickly diversified and took over.” Dr. Collaboration Kraft with Michel Mergel of the University of West Bohemia.
The research is part of the Renaissance of Phosphate Studies, a project that spans across disciplines and timeframes. Chemists are exploring how phosphates seasoned the prebiotic broth that gave rise to life in the first place, while materials scientists toy with the element into startling new colors and shapes.
“If you heat up phosphorous under different conditions, different temperatures, different pressures, and weird things start to happen,” said Andrea Sella, professor of inorganic chemistry at University College London. “You get red fiber shapes, black metallic shapes, and purple shapes.” You can also stack layers of phosphorous atoms and then separate them into very thin, flexible sheets called phosphorene, all with the goal of controlling the flow of electrons and light particles on which the technology relies. “We’ve only just scratched the surface of what this element can do,” said Dr. Silla.
Phosphorous was discovered in the late 17th century by a Hamburg chemist, Henning Brand, who inadvertently isolated it while searching for a “philosopher’s stone” that would turn ordinary metals into gold. Experimenting with loads of the golden liquid he knows best – human urine – popped the brand with a strange substance that lacked any Midas touch but glowed in the dark, leading Brand to call it phosphorous, the Greek name for “bringing light.”
This pure form of the element, called white phosphorous, turned out to be toxic and flammable and so was used in the war, to make the tracer bullets, smoke screens, and Allied firebombs that devastated Brand’s hometown during World War II.
WP also won grim Dickensian fame in the 19th century, when it was added to the tips of matches to produce “strike anywhere” matches. Girls and women toiling in poorly ventilated factories producing the very popular product were sometimes exposed to so much phosphorous vapor that they developed “thin jaw,” a horrific condition in which their gums receded, their teeth fell out, and the bones in their jaws loosened. According to historian Louise Rowe, matchmakers’ struggle for safer working conditions helped spur the modern union movement.
Pure phosphorous does not exist in nature, but it is bound to oxygen, like phosphates, and this molecular trade union, the phosphorous-oxygen bond, “is fundamental to why biology works,” Matthew Bowner, an organic chemist at University College London, said. The body stores and burns energy by making and breaking the phosphate bonds found in the cell’s small monetary machinery, the molecules of adenosine triphosphate, known as ATP. The phosphate recycling process is relentless, said Dr. Bowner, “essentially converting your body weight into ATP each day.”
Phosphate combines with sugar to form the backbone of DNA, where it holds a meaningful arrangement of letters of genetic information that would otherwise collapse into the alphabet soup. Phosphates conspire with lipid molecules to encapsulate each cell with a vigilant membrane that always determines what goes in and what to avoid. Proteins send messages to each other by exchanging phosphate packages.
Behind the amazing benefit of phosphates, a negative charge prevents unwanted leakage. “You can only put in the power and let it out when you want to,” said Dr. Bowner. “It will not seep into the environment.” By contrast, he said, the equivalent carbon-based molecule, called a carbonate, dissolves easily in water: “If you pair DNA with carbons instead of phosphates, it will all disintegrate.” Dr. Bowner joked that we should consider life based on phosphates rather than carbon.
However, unlike the other major components of life – carbon, nitrogen, oxygen and hydrogen – phosphate molecules do not have a gas phase. “It’s too big to fly,” said Dr. Silla. Phosphates jump into the game of life through erosion of rocks, decomposition of organisms, or excreta such as urine or guano. Understanding the effect of phosphate fluxes over time is a major research endeavor.
One lingering puzzle is how early life got its start on phosphate. Given how important phosphate is to every aspect of biology, the primitive aqueous setting in which the first cells arose must have been rich in phosphate. “However, most natural waters on Earth today are very scanty in terms of phosphates,” said Nicholas Tosca, a geochemist at the University of Cambridge. “We expected the same thing to be true early on on planet Earth.” He explained that he believed that iron works to isolate phosphates.
Dr Tosca and colleagues at Cambridge addressed the problem of the origin of life In a study recently published in Nature Communications,. The researchers decided to reconsider the assumption, asking: What about earlier, when there was much less oxygen around? They knew that oxygen converts iron into a form that strongly stacks phosphate. What would happen if oxygen was removed from the equation? The researchers created artificial seawater in a large, oxygen-free glove box and discovered that, certainly, under these conditions, dissolved iron left most of the phosphate alone, presumably available to any protocells in the neighborhood.
In the paper Trends in Ecology and Evolution, Dr. Kraft similarly suggested that the Cambrian seas were relatively phosphate-rich. Animals can absorb so much, in fact, that they can make thick, durable shells, like the hardest tissue in the human body – the phosphate enamel of our teeth.
“It’s a huge advantage to have these shells,” Dr. Kraft said. In comparison, the shell of modern mollusks, made of calcium carbonate, cracks easily under the feet of beaches. But as the seas crowded and bony fish appeared, the supply of phosphates dwindled, and the brachiopods could no longer freely search for what they needed to build their expensive housing. Bony fish were wise in their use of phosphate as a building material: their teeth, a few parts of the skeleton, and that was it. Because they are on the move, the fish can trap any phosphates and other nutrients that are filtered from the land into the sea, before they reach the hard, clumping shells below.
Phosphates were dominated by vertebrates, and nothing could stop them now.
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