sábado, 23 de agosto de 2008

Selección del Complexity Digest - Agosto

Birds Are Tracking Climate Warming, But Not Fast Enough, Proc. Biol. Sc.

Excerpt: Range shifts of many species are now documented as a response to global warming. But whether these observed changes are occurring fast enough remains uncertain and hardly quantifiable. Here, we developed a simple framework to measure change in community composition in response to climate warming. This framework is based on a community temperature index (CTI) that directly reflects, for a given species assemblage, the balance between low- and high-temperature dwelling species. Using data from the French breeding bird survey, we first found a strong increase in CTI over the last two decades revealing that birds are rapidly tracking climate warming. (...)

Ecology: A Matter Of Timing, Science

Excerpts: Climate change is causing shifts in the distribution and phenology of many plants and animals. Birds have played a key role in detecting these changes, because long-term data are available on the distribution, migration, and breeding of many species. Studies of the timing of egg laying--a key trait with extensive records dating back half a century for some species--are providing crucial insights into the mechanisms that underlie the response to climate change.
  • Source: Ecology: A Matter Of Timing, Bruce E. Lyon, Alexis S. Chaine, David W. Winkler, DOI: 10.1126/science.1159822, Science : Vol. 321. no. 5892, pp. 1051 - 1052, 08/08/22

Self-Destructive Cooperation Mediated By Phenotypic Noise, Nature

Excerpts: In many biological examples of cooperation, individuals that cooperate cannot benefit from the resulting public good. This is especially clear in cases of self-destructive cooperation, where individuals die when helping others. If self-destructive cooperation is genetically encoded, these genes can only be maintained if they are expressed by just a fraction of their carriers, whereas the other fraction benefits from the public good. One mechanism that can mediate this differentiation into two phenotypically different sub-populations is phenotypic noise. Here we show that noisy expression of self-destructive cooperation can evolve if individuals that have a higher probability for self-destruction have, on average, access to larger public goods.

Exploding Chromosomes Fuel Research About Evolution, Innovations-report

Excerpt: Human cells somehow squeeze two meters of double-stranded DNA into the space of a typical chromosome, a package 10,000 times smaller than the volume of genetic material it contains. Now research into single-celled, aquatic algae called dinoflagellates is showing that these and related organisms may have evolved more than one way to achieve this feat of genetic packing. Even so, the evolution of chromosomes in dinoflagellates, humans and other mammals seem to share a common biochemical basis, (...). Packing the whole length of DNA into tiny chromosomes is problematic because DNA carries a negative charge that, unless neutralized, prevents any attempt at folding (...).

Genomics: 'Simple' Animal's Genome Proves Unexpectedly Complex, Science

Excerpts: Aptly named "sticky hairy plate," Trichoplax adhaerens barely qualifies as an animal. About 1 millimeter long and covered with cilia, this flat marine organism lacks a stomach, muscles, nerves, and gonads, even a head. It glides along like an amoeba, its lower layer of cells releasing enzymes that digest algae beneath its ever-changing body, and it reproduces by splitting or budding off progeny. Yet this animal's genome looks surprisingly like ours, says Daniel Rokhsar, an evolutionary biologist at the University of California, Berkeley (UCB) and the U.S. Department of Energy Joint Genome Institute in Walnut Creek, California. Its 98 million DNA base pairs include many of the genes responsible for guiding the development of other animals' complex shapes and organs, he and his colleagues report in the 21 August issue of Nature.

Animal Behaviour: Crowd Control, Nature

Excerpts: Many researchers would expect parasitic infection rates to increase as groups of animals get bigger and more hosts are available. Contrary to this, researchers reveal that as groups of red colobus monkeys (Procolobus rufomitratus) get larger, they have fewer parasites.

Tamaini Snaith at McGill University in Montreal, Canada, and her colleagues made the discovery while studying the monkeys in Uganda. They tested faeces for parasites and monitored group dynamics. The researchers noticed that large groups tended to spread out more than smaller ones, and suggest that this could lower infection rates.

Evolutionary Biology: Deciphering the Genetics of Evolution, Science

Excerpts: Powerful personalities in evolutionary biology have been tussling over how the genome changes to set the stage for evolution. (...)

Early suggestions that gene regulation could be important to evolution came in the 1970s from work by bacterial geneticists showing a link between gene expression and enzyme activity in bacteria. About the same time, Allan Wilson and Mary-Claire King of the University of California, Berkeley, concluded that genes and proteins of chimps and humans are so similar that our bipedal, hairless existence must be the product of changes in when, where, and to what degree those genes and proteins come into play. (...).

Evolution of Evolvability in Gene Regulatory Networks, PLoS Comput Biol

Excerpt: A cell receives signals both from its internal and external environment and responds by changing the expression of genes. In this manner the cell adjusts to heat, osmotic pressures and other circumstances during its lifetime. Over long timescales, the network of interacting genes and its regulatory actions also undergo evolutionary adaptation. Yet how do such networks evolve and become adapted?
In this paper we describe the study of a simple model of gene regulatory networks, focusing solely on evolutionary adaptation most fit.

Astronomy: Planetary System Formation, Science

Excerpts: To date, 307 extrasolar planets have been discovered and 29 multipleplanet systems have been identified (1, 2). The masses of the planets range from a few Earth masses up to several Jupiter masses, with orbital periods ranging from slightly over 1 day to several years. Unlike in our solar system, the orbital eccentricities of the extrasolar gas giant-sized planets may be large.

Do Subatomic Particles Have Free Will?, Science News

Excerpts: If we have free will, so do subatomic particles, mathematicians claim to prove. (...)

They used a pure mathematical argument to show that there is no way the particle can choose spins around every imaginable axis in a way that is consistent with the 1-0-1 rule. Indeed, there is a set of just 33 axes that are enough to force the particle into a paradox. It could choose spins around the first 32 axes that conform with the rule, but for the last, neither 0 nor non-zero would do.

Differential Selection According To The Degree Of Cheating In A Status Signal, Biol. Lett.

Excerpts: The maintenance of honesty in a badge-of-status system is not fully understood, despite numerous empirical and theoretical studies. Our experiment examined the relationship between a status signal and winter survival, and the long-term costs of cheating, by manipulating badge size in male house sparrows, Passer domesticus. The effect of badge-size manipulation on survival was complex owing to the significant interactions between the treatments and original (natural) badge size, and between the treatments and age classes (yearlings and older birds). (...) This indicates that differential selection can act on a trait according to the degree of cheating.

Brain Will Be Battlefield Of Future, Warns US Intelligence Report, Guardian

On the battlefield, bullets may be replaced with "pharmacological land mines" that release drugs to incapacitate soldiers on contact, while scanners and other electronic devices could be developed to identify suspects from their brain activity and even disrupt their ability to tell lies when questioned, the report says. (...)

The report highlights one electronic technique, called transcranial direct current stimulation, which involves using electrical pulses to interfere with the firing of neurons in the brain and has been shown to delay a person's ability to tell a lie.

Survival Of The Fittest: Even Cancer Cells Follow The Laws Of Evolution, ScienceDaily

Scientists (...) discovered that the underlying process in tumor formation is the same as for life itself-evolution. After analyzing a half million gene mutations, the researchers found that although different gene mutations control different cancer pathways, each pathway was controlled by only one set of gene mutations. This suggests that a molecular "survival of the fittest" scenario plays out in every living creature as gene mutations strive for ultimate survival through cancerous tumors. This finding (...) improves our understanding of how evolution shapes life in all forms, while laying a foundation for new cancer drugs and treatments. (...)

A Blueprint to Regenerate Limbs, Technology review

Growing limbs: The axolotl salamander is one of the only vertebrates that can regrow entire limbs as an adult. Scientists are now sequencing parts of its unusually large genome in order to understand the genetic basis for this capability.
Credit: Jeramiah Smith
Probing the salamander genome reveals clues to its remarkable ability to regrow damaged limbs and organs. (...)

In order to quickly identify sections of the salamander's genome involved in regeneration, the scientists sequenced genes that were most highly expressed during limb-bud formation and growth. They found that at least 10,000 genes were transcribed during regeneration. Approximately 9,000 of those seem to have related human versions, but there appear to be a few thousand more that don't resemble known genes. "We think many of them are genes that evolved uniquely in salamanders to help with this process," (...).

Slave Ants Rebel, Science News

Members of a species of ants captured to work as slaves rebel against their captors by destroying the pupae they were enslaved to nurture.
Credit: Alexandra Achenbach/ Ludwig-Maximilians University
Killing sprees by slave nannies could be an overlooked form of resistance, Foitzik suggests. The baby-killing offers any kin in nearby colonies some protection from slave-makers, since the kidnapper queen's offspring make up the raiding parties. Paring back their number cuts back the raiding power. Foitzik proposes that this benefit to kin could drive the evolution of the trait.

"This is evolution to be a bad nanny," (...).

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