The mysterious lull in vertebrate colonization of land is known as Romer's Gap, named for the Yale University paleontologist, Alfred Romer, who first recognized it. But the term has typically been applied only to pre-dinosaur amphibians, and there has been little understanding of why the gap occurred.
Now a team of scientists led by University of Washington paleontologist Peter Ward has found a similar gap during the same period among non-marine arthropods, largely insects and spiders, and they believe a precipitous drop in the oxygen content of Earth's atmosphere is responsible.
"These two groups acted exactly the same way. They proliferated, then they went away, and then they reappeared and multiplied like crazy," said Ward, a UW professor of biology and of Earth and space sciences.
He notes that atmospheric oxygen rose sharply at the end of the Silurian period about 415 million years ago, to reach a level of about 22 percent of the atmosphere, similar to today's oxygen content. But 55 million years later, atmospheric oxygen levels sank to 10 percent to 13 percent. The level remained low for 30 million years – during which Romer's Gap occurred – then shot up again, and vertebrates and arthropods again began moving from the sea to land.
"It matches two waves of colonization of the land," Ward said. "In the first wave the animals' lungs couldn't have been very good and when the oxygen level dropped it had to be hard for the vertebrates coming out of the water. I wonder if there is a minimum level of oxygen that has to be reached or nothing could ever have gotten out of the water."
Dinosaurs first appeared in the last part of the Triassic period, about 230 million years ago. That was during one of the lowest ebbs of atmospheric oxygen content of the last 500 million years, but he speculates that it took some time, until oxygen levels rose appreciably, before dinosaurs grew to their familiar gargantuan sizes.
"Dinosaurs thrived and nothing else did. There's an explanation for that, and it is that the air sac breathing system in dinosaurs and their descendants, modern birds, is more efficient than systems used by other organisms," Ward said.
He and his colleagues tested that hypothesis by examining the breathing system used by birds. They found that at sea level birds breathe 30 percent more efficiently than mammals and at 5,000 feet in elevation birds are 200 percent more efficient.
Ward pictures a world in which dinosaurs were able to adapt to low atmospheric oxygen content relatively easily, and when oxygen levels rose the dinosaurs developed into giant creatures that dominated the Earth.
"I think of dinosaurs as the high-altitude Denver athletes of their day. They ran rings around their prey," he said.
Ward also began to wonder whether respiratory needs dictated how other organisms' bodies developed. He thought that perhaps, rather than being based on feeding and movement, body shape and design might largely be determined by respiratory efficiency. For instance, a mollusk shell is typically thought of as protection for the marine creature, he said, but it turns out the shell actually channels water across the gill to deliver oxygen.
"An unshelled mollusk has a far greater respiratory problem than a shelled mollusk," Ward said. "In many groups the shell is an active part of the respiratory system."
Vince Stricherz | EurekAlert!
Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union
UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences