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Dating Mammalian Evolution

Fri, 28 Mar 2014 15:14:37 +0000

When the age of the dinosaurs ended around 65 million years ago, mammals stepped in to fill the gap, and the age of the placentals began. However, whether early placental mammals were already present on Earth before the demise of the dinosaurs has been the subject of a long standing debate. Recent research in GEE [...]


The Delicate Balance of Effect and Response

Tue, 18 Feb 2014 11:50:36 +0000

We may not always be aware of it, but many wild plants, animals, fungi and even bacteria, provide crucial services to us which keep the ecosystems of Earth functioning. Environmental changes caused by human activities are now threatening many species, and those that cannot withstand these changes may be lost forever, potentially taking the services [...]


It’s All in the Wrist

Fri, 20 Dec 2013 16:18:20 +0000

The evolution of the primate wrist has been dramatic, enabling primates to adapt to a wide variety of lifestyles and walking styles, including tree-swinging, climbing and terrestrial walking both on four legs and two. In hominids, the evolution of the bipedal gait freed up the forelimbs for tool use, and the wrist evolved independently from [...]


The Transcriptional Profile of A ‘Wingman’

Wed, 27 Nov 2013 14:25:48 +0000

In many species, males have special adaptations to attract females. From antlers to stalk-eyes, to bright plumage and beards, males across the animal kingdom work hard to look attractive to the opposite sex. In some species, looking good isn’t enough, though. Male wild turkeys need a less attractive ‘wingman’ to help him attract a woman. [...]


Damage and Fidelity: The Role of the Female Germline in mtDNA Inheritance

Mon, 11 Nov 2013 15:13:12 +0000

Billions of years ago, one single-celled organism engulfed another, beginning a symbiotic interaction that would change live on Earth forever. The mitochondria are what remains of this symbiotic event, and are responsible for producing energy in all eukaryotic cells. Derived from a free-living organism, they carry their own genes, but these genes are at risk [...]


Orgin of life emerged from cell membrane bioenergetics

20 December 2012

A coherent pathway which starts from no more than rocks, water and carbon dioxide and leads to the emergence of the strange bio-energetic properties of living cells, has been been traced for the first time in a major hypothesis paper in Cell this week.

At the origin of life, before the emergence of evolution-refined enzymes that make reactions more efficient, the first protocells must have needed a vast amount of energy to drive their metabolism and their replication.

So where did it all that energy come from on the early Earth, and how did it get focused into driving the organic chemistry required for life?

The answer lies in the chemistry of deep-sea hydrothermal vents. In their paper Nick Lane (UCL, Genetics, Evolution and Environment) and Bill Martin (University of Dusseldorf) address the question of where all this energy came from –- and why all life as we know it conserves energy in the peculiar form of ion gradients across membranes.

Life is, in effect, a side-reaction of an energy-harnessing reaction. Living organisms require vast amounts of energy to go on living. Humans consume more than a kilogram ( more than 700 litres) of oxygen every day, exhaling it as carbon dioxide. The simplest cells, growing from the reaction of hydrogen with carbon dioxide, produce about 40 times as much waste product from their respiration as organic carbon (by mass). In all these cases, the energy derived from respiration is stored in the form of ion gradients over membranes.

This strange trait is as universal to life as the genetic code itself. Lane and Martin show that bacteria capable of growing on no more than hydrogen and carbon dioxide are remarkably similar in the details of their carbon and energy metabolism to the far-from-equilibrium chemistry occurring in a particular type of deep-sea hydrothermal vent, known as alkaline hydrothermal vents.

Based on measured values, they calculate that natural proton gradients, acting across thin semi-conducting iron-sulfur mineral walls, could have driven the assimilation of organic carbon, giving rise to protocells within the microporous labyrinth of these vents.

They go on to demonstrate that such protocells are limited by their own permeability, which ultimately forced them to transduce natural proton gradients into biochemical sodium gradients, at no net energetic cost, using a simple Na+/H+ transporter. Their hypothesis predicts a core set of proteins required for early energy conservation, and explains the puzzling promiscuity of respiratory proteins for both protons and sodium ions.

These considerations could also explain the deep divergence between bacteria and archaea (single celled microorganisms) . For the first time, says Lane, "It is possible to trace a coherent pathway leading from no more than rocks, water and carbon dioxide to the strange bioenergetic properties of all cells living today."

Further reading: Nature News How life emerged from deep-sea rocks

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