Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




EARLY EARTH
New data challenge old views about evolution of early life
by Staff Writers
Riverside CA (SPX) Dec 28, 2012


Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc-binding protein structures.

A research team led by biogeochemists at the University of California, Riverside has tested a popular hypothesis in paleo-ocean chemistry, and proved it false. The fossil record indicates that eukaryotes - single-celled and multicellular organisms with more complex cellular structures compared to prokaryotes, such as bacteria - show limited morphological and functional diversity before 800-600 million years ago.

Many researchers attribute the delayed diversification and proliferation of eukaryotes, which culminated in the appearance of complex animals about 600 million years ago, to very low levels of the trace metal zinc in seawater.

As it is for humans, zinc is essential for a wide range of basic cellular processes. Zinc-binding proteins, primarily located in the cell nucleus, are involved in the regulation of gene transcription.

Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc-binding protein structures. Zinc is, therefore, of particular importance to eukaryotic organisms. And so it is not a stretch to blame the 1-2-billion-year delay in the diversification of eukaryotes on low bioavailability of this trace metal.

But after analyzing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, the researchers found that the shales reflect high seawater zinc availability and that zinc concentrations during the Proterozoic (2.5 billion to 542 million years ago) were similar to modern concentrations. Zinc, the researchers posit, was never biolimiting.

Study results appear in Nature Geoscience.

"We argue that the concentration of zinc in ancient marine black shales is directly related to the concentrations of zinc in seawater and show that zinc is abundant in these rocks throughout Earth's history," said Clint Scott, the first author of the research paper and a former UC Riverside graduate student. "We found no evidence for zinc biolimitation in seawater."

Scott, now a research geologist with the U.S. Geological Survey, explained that the connection between zinc limitation and the evolution of eukaryotes was based largely on the hypothesis that Proterozoic oceans were broadly sulfidic. Under broadly sulfidic conditions, zinc should have been scarce because it would have rapidly precipitated in the oceans, he explained.

"However, a 2011 research paper in Nature also published by our group at UCR demonstrated that Proterozoic oceans were more likely broadly ferruginous - that is, low in oxygen and iron-rich - and that sulfidic conditions were more restricted than previously thought," said Scott, who performed the research in the lab of Timothy Lyons, a professor of biogeochemistry and the principal investigator of the research project.

The research team argues that ferruginous deep oceans, combined with large hydrothermal fluxes of zinc via volcanic activity on the seafloor, maintained high levels of dissolved zinc throughout the oceans and provided a relatively stable marine reservoir of the trace metal over the past 2.7 billion years.

"The key challenge in understanding the early evolution of life is recognizing the environmental conditions under which that life first appeared and diversified," Lyons said.

"We have taken a very direct approach that specifically tracks the availability of essential micronutrients, and, to our surprise, zinc supplies in ancient seawater were much higher and less variable than previously imagined.

"We can imagine for the first time," he quipped, "that zinc supplements were not on the shopping lists of our early eukaryotic ancestors, and so we better find another reason to explain the mysterious delay in their rise in the ocean."

Scott, who graduated with a doctoral degree in geological sciences from UCR in 2009, and Lyons were joined in the study by Noah J. Planavsky, a former UCR graduate student in Lyons' lab; Chris L. Dupont at the J. Craig Venter Institute, La Jolla, Calif.; Brian Kendall and Ariel D. Anbar at Arizona State University; Benjamin C. Gill at Virginia Polytechnic Institute and State University and also a former member of the Lyons lab; Leslie J. Robbins and Kurt O. Konhauser at the University of Alberta, Canada; Kathryn F. Husband and Simon W. Poulton at the University of Leeds, United Kingdom; Gail L. Arnold at the Max Planck Institute for Marine Microbiology, Germany; Boswell A. Wing at McGill University, Canada; and Andrey Bekker at the University of Manitoba, Canada. The idea for the study was a direct consequence of the 2011 Nature paper by Planavsky, Scott, Lyons and others that challenged the hypothesis of broadly sulfidic oceans.

.


Related Links
University of California - Riverside
Explore The Early Earth at TerraDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





EARLY EARTH
Ups and downs of biodiversity after mass extinction
Zurich, Switzerland (SPX) Dec 27, 2012
The climate after the largest mass extinction so far 252 million years ago was cool, later very warm and then cool again. Thanks to the cooler temperatures, the diversity of marine fauna ballooned, as paleontologists from the University of Zurich have reconstructed. The warmer climate, coupled with a high CO2 level in the atmosphere, initially gave rise to new, short-lived species. In the ... read more


EARLY EARTH
Fukushima operator boosts compensation estimate

N.Z. quake city puts faith in cardboard cathedral

China suspends officials after 11 kids die in road wreck

'No Christmas' for Philippine typhoon victims

EARLY EARTH
Liquid crystal research, future applications advance

US probes HP's Autonomy fraud allegations

UKube-1 Signs up for Launch and Completes Thermal Vacuum Testing

China sets first-half rare earth export quota for 2013

EARLY EARTH
Smaller Colorado River projected for coming decades

China's boom savages coral reefs: study

Spanish consumers prefer national fish

Study reveals that animals contribute to seagrass dispersal

EARLY EARTH
W. Antarctic warming among world's fastest

Antarctic ice sheet warming faster than thought: study

NASA's Operation IceBridge Data Brings New Twist to Sea Ice Forecasting

Chief's hunger strike fuels Canada aboriginal drive

EARLY EARTH
Bumblebees do best where there is less pavement and more floral diversity

Why some grasses evolved a more efficient photosynthesis and others didn't

Small wasps to control a big pest?

Unraveling the threads: Simplest cotton genome offers clues for fiber improvements

EARLY EARTH
Fresh cyclone brews in Pacific

Two dead as Malaysian floods subside

When the ice melts, the Earth spews fire

1,500 Nicaraguan farmers stay put despite volcano warning

EARLY EARTH
Namibia rhino deaths raise fears of widening poaching crisis

Nigerian troops kill five Islamists in restive north

Mali PM calls for swift African military action

Chad lifts expulsion order against critical Italian bishop

EARLY EARTH
Decision to give a group effort in the brain

Scientists construct first map of how the brain organizes everything we see

Do palm trees hold the key to immortality?

Study: Human hands evolved as weapons




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement