Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Life in a greenhouse world

28.10.2002


What constrained the evolution of life during the very hot early Earth? Was a simple drop in temperature largely responsible for the emergence of cyanobacteria, a large and varied group of bacteria with chlorophyll that carry out photosynthesis in the presence of light and air with concomitant production of oxygen? Was it a reduction in carbon-dioxide levels?



Geochemist David Schwartzman of Howard University and Ken Caldeira of the Climate and Carbon Cycle Group at Lawrence Livermore National Laboratory have a different view. Looking at how feedback operates in Earth systems, they propose that the transition from a carbon-dioxide dominated greenhouse world to one dominated by methane actually did the trick.

Schwartzman and Caldeira will present findings of their research on Monday, October 28, at the annual meeting of the Geological Society of America in Denver, CO.


It’s been argued that surface temperatures of 80-60 degrees centigrade kept the lid on evolution during the carbon-dioxide dominated greenhouse world of 3.8 to 2.5 billion years ago. Dominant forms of life were very simple, consisting of prokaryotes (cells without nuclei that reproduce asexually) and eucaryotes (more advanced cells with nuclei). Metazoa, the animal kingdom, did not emerge until 0.7 to 1.5 billion year ago, when temperatures apparently dropped below their upper limit.

"I have argued that primitive organisms emerged once their upper temperature limit was reached as the relatively high climatic temperatures of the Archean declined," says Schwartzman. "It appeared likely that methane replaced carbon dioxide as the dominant gas in the greenhouse atmosphere of early Earth by about 2.8 billion years ago. So we began to look at the dynamics of methane dominance, reduced levels of CO2, reduced surface temperatures, and the appearance of cyanobacteria. The question that arose for me is, ’Is it a coincidence that the first good evidence for methane as a significant component of Earth’s atmosphere occurred at the same time as analogous evidence for the first cyanobacteria?’"

Schwartzman and Caldeira followed up the proposal of Charles Dismukes and coworkers that now extinct bacteria were performing oxygen-based photosynthesis before cyanobacteria came onto the scene. In a CO2 dominated world, these early oxygenic photosynthesizers split bicarbonate instead of water as the source of oxygen. They apparently boosted organic productivity and caused greater methane production by methanogens living in the ocean.

"It takes far less methane to maintain climatic temperatures than it does carbon dioxide," says Schwartzman.

As methane became dominant, CO2 levels dropped dramatically. Cyanobacteria then emerged and began oxygenic photosynthesis by splitting water as the source of oxygen. According to Schwartzman, only when atmospheric oxygen levels began to rise some 2.2 billion years ago did a CO2-concentrating mechanism emerge, an adaptation to declining CO2/02 ratios in the external environment.

Thus, global constraints on evolution appeared to have included carbon dioxide as well as oxygen levels in the atmosphere along with surface temperature. All the former have been strongly influenced by biological evolution in a complex set of feedbacks, an essential aspect of biospheric evolution. "The classical paradigm of evolution, that changes in the local environment lead to natural selection, should be rethought to include these feedbacks on a global scale. We hope that our hypothesis will be tested by looking more closely at the extant geologic record of the proposed transition as well as the insights from the study of photosynthesis and molecular biology of modern organisms," says Schwartzman.


CONTACT INFORMATION

During the GSA Annual Meeting, Oct. 27-30, contact Christa Stratton at the GSA Newsroom in the Colorado Convention Center, Denver, Colorado, for assistance and to arrange for interviews: 303-228-8565.

The abstract for this presentation is available at: http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_44609.htm

Post-meeting contact information:

David W. Schwartzman
Dept. of Biology
Howard University
Washington, DC 20059
acairns@geosociety.orgdws@scs.howard.edu
202-806-6926

Ann Cairns
Director of Communications
Geological Society of America
acairns@geosociety.org
303-357-1056


Ann Cairns | EurekAlert!
Further information:
http://www.geosociety.org/
http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_44609.htm

More articles from Life Sciences:

nachricht One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>