How Earth's Atmosphere Changed

A DENSE RAINFOREST or other verdant terrestrial vegetation may be what first comes to mind at the mention of photosynthesis. Yet the clouds of phytoplankton that fill the oceans are the major drivers of that process in nature. 

The plantlike single-celled aquatic microbes generate more than 50 percent of the oxygen in the atmosphere, and they absorb nearly half of the carbon dioxide, converting it into the glucose, fats, proteins and other organic molecules that nourish the food web of the oceans.

A recently published study in Current Biology finally pins down the source of this unparalleled photosynthetic efficiency, which has long baffled scientists. The new research found that some phytoplankton are equipped with an extra internal membrane that carries a “proton pump” enzyme that supercharges their ability to convert carbon dioxide into other substances. 

The enhancements due to this one protein modification seem to contribute to the production of nearly 12 percent of the oxygen in the air and as much as 25 percent of all the carbon “fixed” (locked into organic compounds) in the ocean.

Surprisingly, that photosynthetic innovation seems to have evolved by chance from a membrane protein that was originally used for digestion in the ancestor of the phytoplankton. 

In addition to explaining the cells’ prowess at photosynthesis, the new work helps to confirm the theory that those phytoplankton arose through a symbiotic alliance between a protozoan and a resilient red alga.

“I find it staggering that a proton enzyme that we have known for so many decades is responsible for maintaining such a crucial phenomenon on Earth,” said Dennis Brown, a cell biologist at Harvard Medical School who studies the functions of membrane proteins and was not involved in the study.

Researchers knew that certain classes of phytoplankton—diatoms, dinoflagellates, and coccolithophores—stand out for their exceptional photosynthetic abilities. 

Those cells are extremely proficient at absorbing carbon dioxide from their environment and directing it to their chloroplasts for photosynthesis, but the details of why they are so good at it haven’t been very clear. A feature unique to those three groups of phytoplankton, however, is that they have an extra membrane around their chloroplasts.  READ MORE...

Giant Dinosaurs Had Tiny Arms

An international team that includes a University of Minnesota Twin Cities researcher has 

discovered a new big, meat-eating dinosaur, dubbed Meraxes gigas (illustrated above), that 

provides clues about the evolution and anatomy of predatory dinosaurs such as the 

Carcharodontosaurus and Tyrannosaurus rex. Credit: Jorge A Gonzalez

Discovery provides insight into the evolution and anatomy of big, carnivorous dinosaurs.

Researchers discovered a new huge, meat-eating dinosaur, dubbed Meraxes gigas. The new dinosaur provides fascinating clues about the evolution and biology of dinosaurs such as the Carcharodontosaurus and Tyrannosaurus rex—particularly, why these creatures had such large skulls and tiny arms.

The study was co-led by University of Minnesota Twin Cities researcher Peter Makovicky and Argentinean colleagues Juan Canale and Sebastian Apesteguía and was published in Current Biology, a peer-reviewed scientific biology journal.


Initially discovered in Patagonia in 2012, scientists have spent the last several years extracting, preparing, and analyzing the Meraxes specimen. The dinosaur is part of the Carcharodontosauridae family. 

This group of giant carnivorous theropods also includes Giganotosaurus, one of the largest known meat-eating dinosaurs and one of the reptilian stars of the recently released “Jurassic World: Dominion” movie.

Though not the largest among carcharodontosaurids, Meraxes was still an imposing animal measuring around 36 feet (11 meters) from snout to tail tip and weighing approximately 9,000 pounds (4,000 kg). 

The researchers recovered the Meraxes, alongside other dinosaurs including several long-necked sauropod specimens, from rocks that are around 90-95 million years old.  READ MORE...