Speaking of Life

To see life, look here:

http://en.citizendium.org/wiki/Life

Citizendium's latest version of its answer to the perennial question:

What is life?

Many other interesting free encyclopedia articles at Citizendium:

http://en.citizendium.org

The Ride of Life

News from the Cardiff Centre for Astrobiology

The Earth moves in many different patterns concurrently. It rotates on an axis, it wobbles its rotation on that axis, it revolves around the sun, it moves with the sun and its system of planets through space in the Milky Way galaxy, and moves with the galaxy's spinning and hurtling away from some and toward other galaxies.

In addition to those patterns, along with the solar system, the Earth bounces alternating bi-directionally through the plane of the galaxy. The denser parts of the galaxy's plane has huge gravitational masses that dislodge comets from their paths, some of which impact Earth. The bounce-throughs occur every 35-40 million years, in keeping with Earth's 36 million year interval of increased comet impacts. Several of Earth's mass extinctions coincide, too.

The researchers who "discovered", in a computational simulation, the bouncing solar system ride, speculate that the bombardments might strew some of Earth's microorganisms through the galaxy, perhaps seeding life elsewhere. Or introducing new life. Perhaps other solar systems do likewise. Imagine, a galactic-wide primordial soup! An alphabet soup spelling 'mother'.

See story at:

http://www.cardiff.ac.uk/news/articles/did-the-solar-system-bounce-finish-the-dinosaurs.html

Did the solar system 'bounce' finish the dinosaurs?

Designer Evolution

Suppose you wanted to direct the evolution of molecular systems that behaved according to parameters you set. By whatever means you implement that, you must have a method for directing evolution of individual molecules toward desired functional properties, since the system must have the appropriate parts to generate its functionality. In that case, you must have a molecule generating factory for the component parts. Starting with enormous numbers of generators of different efficiency/capacity, and limiting the substrate precursors of the desired molecules, iteratively in rapid succession, and imposing the parameters defining the desired functional molecule, natural selection will favor preservation of the high-capacity, fast-reacting, efficient generators that yield the targeted molecule.

 

That process admits of automation on a chip, as demonstrated by Brian M. Paegel and Gerald F. Joyce, in the Departments of Chemistry and Molecular Biology, of the Scripps Research Institute, La Jolla, California, and in the Skaggs Institute for Chemical Biology, of the Scripps Research Institute, La Jolla, California, both in the U.S.

 

The procedure produces a continuous stream of real-time data, giving the experimenter a record of the evolutionary course in terms of population size and heterogeneity, and growth conditions, including availability of limiting resources. Each microchip contains multiple microfluidic circuits independently addressable. The method costs modestly, so the process makes Darwinian evolution readily accessable. As easy almost as implementing the evolution of the system on a computer.

 

Darwinian Evolution on a Chip. Paegel BM, Joyce GF. PLoS Biology Vol. 6, No. 4, e85 doi:10.1371/journal.pbio.0060085

Chip-Based Designer Molecular Evolution

Suppose you wanted to direct the evolution of molecular systems that behaved according to parameters you set. By whatever means you implement that, you must have a method for directing evolution of individual molecules toward desired functional properties, since the system must have the appropriate parts to generate its functionality. In that case, you must have a molecule generating factory for the component parts. Starting with enormous numbers of generators of different efficiency/capacity, and limiting the substrate precursors of the desired molecules, iteratively in rapid succession, and imposing the parameters defining the desired functional molecule, natural selection will favor preservation of the high-capacity, fast-reacting, efficient generators that yield the targeted molecule.

 

That process admits of automation on a chip, as demonstrated by Brian M. Paegel and Gerald F. Joyce, in the Departments of Chemistry and Molecular Biology, of the Scripps Research Institute, La Jolla, California, and in the Skaggs Institute for Chemical Biology, of the Scripps Research Institute, La Jolla, California, both in the U.S.

 

The procedure produces a continuous stream of real-time data, giving the experimenter a record of the evolutionary course in terms of population size and heterogeneity, and growth conditions, including availability of limiting resources. Each microchip contains multiple microfluidic circuits independently addressable. The method costs modestly, so the process makes Darwinian evolution readily accessible. As easy almost as implementing the evolution of the system on a computer.

Darwinian Evolution on a Chip. Paegel BM, Joyce GF. PLoS Biology Vol. 6, No. 4, e85 doi:10.1371/journal.pbio.0060085

Citizendium Grows

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Biologists might find interesting the many articles guided by the Biology workgroup. See for example

Biology and Biology/Draft

Life and Life/Draft

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Then go to the list of all biology articles, here.

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Questions?

Monkeys Learn Their Numbers

Diester I,Nieder A (2007) Semantic Associations between Signs and Numerical Categories in the Prefrontal Cortex. PLoS Biol 5(11): e294 doi:10.1371/journal.pbio.0050294

From the Abstract:

• The utilization of symbols such as words and numbers as mental tools endows humans with unrivalled cognitive flexibility.
  
• In the number domain, a fundamental first step for the acquisition of numerical symbols is the semantic association of signs with cardinalities.
  
• We explored the primitives of such a semantic mapping process by recording single-cell activity in the monkey prefrontal and parietal cortices, brain structures critically involved in numerical cognition.
  
• Monkeys were trained to associate visual shapes with varying numbers of items in a matching task.
  
• After this long-term learning process, we found that the responses of many prefrontal neurons to the visual shapes reflected the associated numerical value in a behaviorally relevant way.
  
• In contrast, such association neurons were rarely found in the parietal lobe.
  
• These findings suggest a cardinal [probably no pun intended] role of the prefrontal cortex in establishing semantic associations between signs and abstract categories, a cognitive precursor that may ultimately give rise to symbolic thinking in linguistic humans.
  

Author Summary:

We use symbols, such as numbers, as mental tools for abstract and precise representations. Humans share with animals a language-independent system for representing numerical quantity, but number symbols are learned during childhood. A first step in the acquisition of number symbols constitutes an association of signs with specific numerical values of sets. To investigate the single-neuron mechanisms of semantic association, we simulated such a mapping process in rhesus monkeys by training them to associate the visual shapes of Arabic numerals with the numerosity of multiple-dot displays. We found that many individual neurons in the prefrontal cortex, but only a few in the posterior parietal cortex, responded in a tuned fashion to the same numerical values of dot sets and associated shapes. We called these neurons association neurons since they establish an associational link between shapes and numerical categories. The distribution of these association neurons across prefrontal and parietal areas resembles activation patterns in children and suggests a precursor of our symbol system in monkeys.

Copyright: © 2007 Diester and Nieder. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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