Ants, Like Humans, Can Change Their Priorities

All animals have to make decisions every day. Where will they live and what will they eat? How will they protect themselves? They often have to make these decisions as a group, too, turning what may seem like a simple choice into a far more nuanced process. So, how do animals know what's best for their survival?

For the first time, Arizona State University researchers have discovered that at least in ants, animals can change their decision-making strategies based on experience. They can also use that experience to weigh different options.

The findings are featured today in the early online edition of the scientific journal Biology Letters, as well as in its Dec. 23 edition.

Co-authors Taka Sasaki and Stephen Pratt, both with ASU's School of Life Sciences, have studied insect collectives, such as ants, for years. Sasaki, a postdoctoral research associate, specializes in adapting psychological theories and experiments that are designed for humans to ants, hoping to understand how the collective decision-making process arises out of individually ignorant ants.

"The interesting thing is we can make decisions and ants can make decisions -- but ants do it collectively," said Sasaki. "So how different are we from ant colonies؟"

To answer this question, Sasaki and Pratt gave a number of Temnothorax rugatulus ant colonies a series of choices between two nests with differing qualities. In one treatment, the entrances of the nests had varied sizes, and in the other, the exposure to light was manipulated. Since these ants prefer both a smaller entrance size and a lower level of light exposure, they had to prioritize.

"It's kind of like a humans and buying a house," said Pratt, an associate professor with the school. "There's so many options to consider -- the size, the number of rooms, the neighborhood, the price, if there's a pool. The list goes on and on. And for the ants it's similar, since they live in cavities that can be dark or light, big or small. With all of these things, just like with a human house, it's very unlikely to find a home that has everything you want."

Pratt continued to explain that because it is impossible to find the perfect habitat, ants make various tradeoffs for certain qualities, ordering them in a queue of most important aspects. But, when faced with a decision between two different homes, the ants displayed a previously unseen level of intelligence.

According to their data, the series of choices the ants faced caused them to re-prioritize their preferences based on the type of decision they faced. Ants that had to choose a nest based on light level prioritized light level over entrance size in the final choice. On the other hand, ants that had to choose a nest based on entrance size ranked light level lower in the later experiment. 

This means that, like people, ants take the past into account when weighing options while making a choice. The difference is that ants somehow manage to do this as a colony without any dissent. While this research builds on groundwork previously laid down by Sasaki and Pratt, the newest experiments have already raised more questions.

"You have hundreds of these ants, and somehow they have to reach a consensus," Pratt said. "How do they do it without anyone in charge to tell them what to do?"

Pratt likened individual ants to individual neurons in the human brain. Both play a key role in the decision-making process, but no one understands how every neuron influences a decision.

Sasaki and Pratt hope to delve deeper into the realm of ant behavior so that one day, they can understand how individual ants influence the colony. Their greater goal is to apply what they discover to help society better understand how humanity can make collective decisions with the same ease ants display.

"This helps us learn how collective decision-making works and how it's different from individual decision-making," said Pratt. "And ants aren't the only animals that make collective decisions -- humans do, too. So maybe we can gain some general insight."

Source : Science Daily


One in Five Sun-Like Stars May Have Earth-Size

Based on a statistical analysis of all the Kepler observations, University of California, Berkeley, and University of Hawaii, Manoa, astronomers now estimate that one in five stars like the sun have planets about the size of Earth and a surface temperature conducive to life.

Given that about 20 percent of stars are sun-like, the researchers say, that amounts to several tens of billions of potentially habitable, Earth-size planets in the Milky Way Galaxy.

"When you look up at the thousands of stars in the night sky, the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away and can be seen with the naked eye. That is amazing," said UC Berkeley graduate student Erik Petigura, who led the analysis of the Kepler data.

"It's been nearly 20 years since the discovery of the first extrasolar planet around a normal star. Since then, we have learned that most stars have planets of some size orbiting them, and that Earth-size planets are relatively common in close-in orbits that are too hot for life," said Andrew Howard, a former UC Berkeley post-doctoral fellow who is now on the faculty of the Institute for Astronomy at the University of Hawaii. "With this result, we've come home, in a sense, by showing that planets like our Earth are relatively common throughout the Milky Way Galaxy."

Petigura, Howard and Geoffrey Marcy, UC Berkeley professor of astronomy, will publish their analysis and findings this week in the online early edition of the journal Proceedings of the National Academy of Sciences.

Earth-size may not mean habitable

"For NASA, this discovery is really important, because future missions will try to take an actual picture of a planet, and the size of the telescope they have to build depends on how close the nearest Earth-size planets are," Howard said. "An abundance of planets orbiting nearby stars simplifies such follow-up missions."

The team cautioned that Earth-size planets in orbits about the size of Earth's are not necessarily hospitable to life, even if they reside in the habitable zone around a star where the temperature is not too hot and not too cold.

"Some may have thick atmospheres, making it so hot at the surface that DNA-like molecules would not survive. Others may have rocky surfaces that could harbor liquid water suitable for living organisms," Marcy said. "We don't know what range of planet types and their environments are suitable for life."

Last week, however, Howard, Marcy and their colleagues provided hope that many such planets actually are rocky and could support liquid water. They reported that one Earth-size planet discovered by Kepler -- albeit, a planet with a likely temperature of 2,000 Kelvin, which is far too hot for life as we know it -- is the same density as Earth and most likely composed of rock and iron, like Earth.

"This gives us some confidence that when we look out into the habitable zone, the planets Erik is describing may be Earth-size, rocky planets," Howard said.

Transiting planets

NASA launched the Kepler space telescope in 2009 to look for planets outside the solar system that cross in front of, or transit, their stars, which causes a slight diminution -- about one hundredth of 1 percent -- in the star's brightness. From among the 150,000 stars photographed every 30 minutes for four years, NASA's Kepler team reported more than 3,000 planet candidates. Many of these are much larger than Earth -- ranging from large planets with thick atmospheres, like Neptune, to gas giants like Jupiter -- or in orbits so close to their stars that they are roasted.

To sort them out, Petigura and his colleagues are using the Keck telescopes in Hawaii to obtain spectra of as many stars as possible. This will help them determine each star's true brightness and calculate the diameter of each transiting planet, with an emphasis on Earth-diameter planets.

Independently, Petigura, Howard and Marcy focused on the 42,000 stars that are like the sun or slightly cooler and smaller, and found 603 candidate planets orbiting them. Only 10 of these were Earth-size, that is, one to two times the diameter of Earth and orbiting their star at a distance where they are heated to lukewarm temperatures suitable for life. The team's definition of habitable is that a planet receives between four times and one-quarter the amount of light that Earth receives from the sun.

A census of extrasolar planets

What distinguishes the team's analysis from previous analyses of Kepler data is that they subjected Petigura's planet-finding algorithms to a battery of tests in order to measure how many habitable zone, Earth-size planets they missed. Petigura actually introduced fake planets into the Kepler data in order to determine which ones his software could detect and which it couldn't.

"What we're doing is taking a census of extrasolar planets, but we can't knock on every door. Only after injecting these fake planets and measuring how many we actually found could we really pin down the number of real planets that we missed," Petigura said.

Accounting for missed planets, as well as the fact that only a small fraction of planets are oriented so that they cross in front of their host star as seen from Earth, allowed them to estimate that 22 percent of all sun-like stars in the galaxy have Earth-size planets in their habitable zones.

"The primary goal of the Kepler mission was to answer the question, 'When you look up in the night sky, what fraction of the stars that you see have Earth-size planets at lukewarm temperatures so that water would not be frozen into ice or vaporized into steam, but remain a liquid, because liquid water is now understood to be the prerequisite for life?'" Marcy said. "Until now, no one knew exactly how common potentially habitable planets were around sun-like stars in the galaxy." 

All of the potentially habitable planets found in the team's survey are around K stars, which are cooler and slightly smaller than the sun, Petigura said. But the researchers' analysis shows that the result for K stars can be extrapolated to G stars like the sun. Had Kepler survived for an extended mission, it would have obtained enough data to directly detect a handful of Earth-size planets in the habitable zones of G-type stars.

"If the stars in the Kepler field are representative of stars in the solar neighborhood, … then the nearest (Earth-size) planet is expected to orbit a star that is less than 12 light-years from Earth and can be seen by the unaided eye," the researchers wrote in their paper. "Future instrumentation to image and take spectra of these Earths need only observe a few dozen nearby stars to detect a sample of Earth-size planets residing in the habitable zones of their host stars."

In January, the team reported a similar analysis of Kepler data for scorched planets that orbit close to their stars. The new, more complete analysis shows that "nature makes about as many planets in hospitable orbits as in close-in orbits," Howard said.

The research was funded by UC Berkeley and the National Science Foundation, with the assistance of the W. M. Keck Observatory and NASA.

Source:Science Daily


How the Universe's Violent Youth Seeded Cosmos With Iron

By detecting an even distribution of iron throughout a massive galaxy cluster, astrophysicists can tell the 10-billion-year-old story of how exploding stars and black holes sowed the early cosmos with heavy elements.

New evidence that iron is spread evenly between the galaxies in one of the largest galaxy clusters in the universe supports the theory that the universe underwent a turbulent and violent youth more than 10 billion years ago. That explosive period was responsible for seeding the cosmos with iron and other heavy elements that are critical to life itself.

Researchers from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), jointly run by Stanford University and the Department of Energy's SLAC National Accelerator Laboratory, shed light on this important era by analyzing 84 sets of X-ray telescope observations from the Japanese-US Suzaku satellite. Their results appear in the Oct. 31 issue of the journal Nature.

In particular, the researchers looked at iron distribution throughout the Perseus cluster, a large grouping of galaxies about 250 million light-years away.

"We saw that iron is spread out between the galaxies remarkably smoothly," said Norbert Werner, an astrophysicist at KIPAC and lead author of the paper. "That means it had to be present in the intergalactic gas before the Perseus cluster formed."

The even distribution of these elements supports the idea that they were created at least 10 billion to 12 billion years ago. According to the paper, during this time of intense star formation, billions of exploding stars created vast quantities of heavy elements in the alchemical furnaces of their own destruction. This was also the epoch when black holes in the hearts of galaxies were at their most energetic.

"The combined energy of these cosmic phenomena must have been strong enough to expel most of the metals from the galaxies at early times and to enrich and mix the intergalactic gas," said co-author and KIPAC graduate student Ondrej Urban.

To settle the question of whether the heavy elements created by supernovae remain mostly in their home galaxies or are spread out through intergalactic space, the researchers looked through the Perseus cluster in eight different directions. They focused on the hot, 10-million-degree gas that fills the spaces between galaxies and found the spectroscopic signature of iron reaching all the way to the cluster's edges.

The researchers estimate that the amount of iron in the cluster is roughly equivalent to the mass of 50 billion suns.

"We think most of the iron came from a single type of supernovae, called Type Ia supernovae," said former KIPAC member and co-author Aurora Simionescu, who is currently with the Japanese Aerospace Exploration Agency as an International Top Young Fellow.

In a Type Ia supernova, a star explodes and releases all its material to the void. The researchers believe that at least 40 billion Type Ia supernovae must have exploded within a relatively short period on cosmological time scales in order to release that much iron and have the force to drive it out of the galaxies.

The results suggest that the Perseus cluster is probably not unique and that iron -- along with other heavy elements -- is evenly spread throughout all massive galaxy clusters, said Steven Allen, a KIPAC associate professor and head of the research team.

"You are older than you think -- or at least, some of the iron in your blood is older, formed in galaxies millions of light years away and billions of years ago," Simionescu said.

The researchers are now looking for iron in other clusters and eagerly awaiting a mission capable of measuring the concentrations of elements in the hot gas with greater accuracy.

"With measurements like these, the Suzaku satellite is having a profound impact on our understanding of how the largest structures in our universe grow," Allen said. "We're really looking forward to what further data can tell us."

The research was supported by the Japanese Aerospace Exploration Agency and by the US Department of Energy.

Source:Science Daily


Glow-in-the-Dark Spray Could Make Night Driving Safer


How can you make roads safer for drivers? One company, known as Pro-Teq, is testing glow-in-the-dark material that can be sprayed onto roadways to help illuminate the way for night drivers.

The U.K.-based company developed a waterproof photoluminescent coating, called Starpath, which absorbs light during the day and gives off an ethereal glow at night, according to Treehugger. The coating is non-reflective and has anti-slip properties, which could reduce the number of accidents on motorways, reported Treehugger. Starpath-covered roads could also help communities save money and energy, since they are bright enough without street lamps.

The technology is currently being tested on walking paths in Christ's Pieces park in Cambridge, England. Applying the spray coating took only 30 minutes, and the walking paths were open to the public four hours later, reported Treehugger.



Longer Life for Humans Linked to Further Loss of Endangered Species

As human life expectancy increases, so does the percentage of invasive and endangered birds and mammals, according to a new study by the University of California, Davis.

The study, published in the September issue of Ecology and Society, examined a combination of 15 social and ecological variables -- from tourism and per capita gross domestic product to water stress and political stability. Then researchers analyzed their correlations with invasive and endangered birds and mammals, which are two indicators of what conservationist Aldo Leopold termed "land sickness," the study said.

Human life expectancy, which is rarely included among indexes that examine human impacts on the environment, surfaced as the key predictor of global invasions and extinctions.

"It's not a random pattern," said lead author Aaron Lotz, a postdoctoral scholar in the Department of Wildlife, Fish and Conservation Biology when the study was conducted. "Out of all this data, that one factor -- human life expectancy -- was the determining factor for endangered and invasive birds and mammals."

The study analyzed data from 100 countries, which included roughly 87 percent of the world's population, 43 percent of global GDP per capita, and covered 74 percent of Earth's total land area. Additional factors considered were agricultural intensity, rainfall, pesticide regulation, energy efficiency, wilderness protection, latitude, export-import ratio, undernourishment, adult literacy, female participation in government, and total population.

The findings include:

 •New Zealand, the United States and the Philippines had among the highest percentages of endangered and invasive birds.

• New Zealand had the highest percentage of all endangered and invasive species combined, largely due to its lack of native terrestrial mammals. The study said that in the past 700 to 800 years since the country was colonized, it has experienced massive invasion by nonindigenous species, resulting in catastrophic biodiversity loss.

• African countries had the lowest percentage of invasive and endangered birds and mammals. These countries have had very little international trade, which limits opportunities for biological invasion.

• As GDP per capita -- a standard measure of affluence -- increased in a country, so did the percentage of invasive birds and mammals.

 •As total biodiversity and total land area increased in a country, so did the percentage of endangered birds. (Biodiversity in this context is not a measure of health but refers to the number of species in an area.)

Lotz said the study's results indicate the need for a better scientific understanding of the complex interactions among humans and their environment.

"Some studies have this view that there's wildlife and then there's us," said Lotz. "But we're part of the ecosystem. We need to start relating humans to the environment in our research and not leave them out of the equation. We need to realize we have a direct link to nature."

Source: Science Daily