Oxygen Levels Were Key to Early Animal Evolution, Strongest Evidence Now Shows

Oxygen Levels Were Key to Early Animal Evolution, Strongest Evidence Now Shows

It has long puzzled scientists why, after 3 billion years of nothing more complex than algae, complex animals suddenly started to appear on Earth. Now, a team of researchers has put forward some of the strongest evidence yet to support the hypothesis that high levels of oxygen in the oceans were crucial for the emergence of skeletal animals 550 million years ago.

The new study is the first to distinguish between bodies of water with low and high levels of oxygen. It shows that poorly oxygenated waters did not support the complex life that evolved immediately prior to the Cambrian period, suggesting the presence of oxygen was a key factor in the appearance of these animals.

The research, based on fieldwork carried out in the Nama Group in Namibia, is published in the journal Nature Communications.

Lead author Dr Rosalie Tostevin completed the study analyses as part of her PhD with UCL Earth Sciences, and is now in the Department of Earth Sciences at Oxford University. She said: ‘The question of why it took so long for complex animal life to appear on Earth has puzzled scientists for a long time. One argument has been that evolution simply doesn’t happen very quickly, but another popular hypothesis suggests that a rise in the level of oxygen in the oceans gave simple life-forms the fuel they needed to evolve skeletons, mobility and other typical features of modern animals.

‘Although there is geochemical evidence for a rise in oxygen in the oceans around the time of the appearance of more complex animals, it has been really difficult to prove a causal link. By teasing apart waters with high and low levels of oxygen, and demonstrating that early skeletal animals were restricted to well-oxygenated waters, we have provided strong evidence that the availability of oxygen was a key requirement for the development of these animals. However, these well-oxygenated environments may have been in short supply, limiting habitat space in the ocean for the earliest animals.’

The team, which included other geochemists, palaeoecologists and geologists from UCL and the universities of Edinburgh, Leeds and Cambridge, as well as the Geological Survey of Namibia, analysed the chemical elemental composition of rock samples from the ancient seafloor in the Nama Group – a group of extremely well-preserved rocks in Namibia that are abundant with fossils of early Cloudina, Namacalathus and Namapoikia animals.

The researchers found that levels of elements such as cerium and iron detected in the rocks showed that low-oxygen conditions occurred between well-oxygenated surface waters and fully ‘anoxic’ deep waters. Although abundant in well-oxygenated environments, early skeletal animals did not occupy oxygen-impoverished regions of the shelf, demonstrating that oxygen availability (probably >10 micromolar) was a key requirement for the development of early animal-based ecosystems.

Professor Graham Shields-Zhou (UCL Earth Sciences), one of the co-authors and Dr Tostevin’s PhD supervisor, said: ‘We honed in on the last 10 million years of the Proterozoic Eon as the interval of Earth’s history when today’s major animal groups first grew shells and churned up the sediment, and found that oxygen levels were important to the relationship between environmental conditions and the early development of animals.’

Advertisements

Hubble Finds Planet Orbiting Pair of Stars

Hubble Finds Planet Orbiting Pair of Stars

Astronomers using NASA’s Hubble Space Telescope, and a trick of nature, have confirmed the existence of a planet orbiting two stars in the system OGLE-2007-BLG-349, located 8,000 light-years away towards the center of our galaxy.

The planet orbits roughly 300 million miles from the stellar duo, about the distance from the asteroid belt to our sun. It completes an orbit around both stars roughly every seven years. The two red dwarf stars are a mere 7 million miles apart, or 14 times the diameter of the moon’s orbit around Earth.

The Hubble observations represent the first time such a three-body system has been confirmed using the gravitational microlensing technique. Gravitational microlensing occurs when the gravity of a foreground star bends and amplifies the light of a background star that momentarily aligns with it. The particular character of the light magnification can reveal clues to the nature of the foreground star and any associated planets.

The three objects were discovered in 2007 by an international collaboration of five different groups: Microlensing Observations in Astrophysics (MOA), the Optical Gravitational Lensing Experiment (OGLE), the Microlensing Follow-up Network (MicroFUN), the Probing Lensing Anomalies Network (PLANET), and the Robonet Collaboration. These ground-based observations uncovered a star and a planet, but a detailed analysis also revealed a third body that astronomers could not definitively identify.

“The ground-based observations suggested two possible scenarios for the three-body system: a Saturn-mass planet orbiting a close binary star pair or a Saturn-mass and an Earth-mass planet orbiting a single star,” explained David Bennett of the NASA Goddard Space Flight Center in Greenbelt, Maryland, the paper’s first author.

The sharpness of the Hubble images allowed the research team to separate the background source star and the lensing star from their neighbors in the very crowded star field. The Hubble observations revealed that the starlight from the foreground lens system was too faint to be a single star, but it had the brightness expected for two closely orbiting red dwarf stars, which are fainter and less massive than our sun. “So, the model with two stars and one planet is the only one consistent with the Hubble data,” Bennett said.

Bennett’s team conducted the follow-up observations with Hubble’s Wide Field Planetary Camera 2. “We were helped in the analysis by the almost perfect alignment of the foreground binary stars with the background star, which greatly magnified the light and allowed us to see the signal of the two stars,” Bennett explained.

Kepler has discovered 10 other planets orbiting tight binary stars, but these are all much closer to their stars than the one studied by Hubble.

Now that the team has shown that microlensing can successfully detect planets orbiting double-star systems, Hubble could provide an essential role in this new realm in the continued search for exoplanets.

The team’s results have been accepted for publication in The Astronomical Journal.

ALMA Explores the Hubble Ultra Deep Field: Deepest Ever Millimetre Observations of Early Universe

ALMA Explores the Hubble Ultra Deep Field: Deepest Ever Millimetre Observations of Early Universe

International teams of astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the distant corner of the Universe first revealed in the iconic images of the Hubble Ultra Deep Field (HUDF). These new ALMA observations are significantly deeper and sharper than previous surveys at millimetre wavelengths. They clearly show how the rate of star formation in young galaxies is closely related to their total mass in stars. They also trace the previously unknown abundance of star-forming gas at different points in time, providing new insights into the “Golden Age” of galaxy formation approximately 10 billion years ago.

The new ALMA results will be published in a series of papers appearing in the Astrophysical Journal and Monthly Notices of the Royal Astronomical Society. These results are also among those being presented this week at the Half a Decade of ALMA conference in Palm Springs, California, USA.

In 2004 the Hubble Ultra Deep Field images — pioneering deep-field observations with the NASA/ESA Hubble Space Telescope — were published. These spectacular pictures probed more deeply than ever before and revealed a menagerie of galaxies stretching back to less than a billion years after the Big Bang. The area was observed several times by Hubble and many other telescopes, resulting in the deepest view of the Universe to date.

Astronomers using ALMA have now surveyed this seemingly unremarkable, but heavily studied, window into the distant Universe for the first time both deeply and sharply in the millimetre range of wavelengths [1]. This allows them to see the faint glow from gas clouds and also the emission from warm dust in galaxies in the early Universe.

ALMA has observed the HUDF for a total of around 50 hours up to now. This is the largest amount of ALMA observing time spent on one area of the sky so far.

A trove of galaxies, rich in carbon monoxide (indicating star-forming potential) were imaged by ALMA (orange) in the Hubble Ultra Deep Field. The blue features are galaxies imaged by Hubble. This image is based on the very deep ALMA survey by Manuel Aravena, Fabian Walter and colleagues, covering about one sixth of the full HUDF area. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble.

One team led by Jim Dunlop (University of Edinburgh, United Kingdom) used ALMA to obtain the first deep, homogeneous ALMA image of a region as large as the HUDF. This data allowed them to clearly match up the galaxies that they detected with objects already seen with Hubble and other facilities.

This study showed clearly for the first time that the stellar mass of a galaxy is the best predictor of star formation rate in the high redshift Universe. They detected essentially all of the high-mass galaxies [2] and virtually nothing else.

Jim Dunlop, lead author on the deep imaging paper sums up its importance: “This is a breakthrough result. For the first time we are properly connecting the visible and ultraviolet light view of the distant Universe from Hubble and far-infrared/millimetre views of the Universe from ALMA.

The second team, led by Manuel Aravena of the Núcleo de Astronomía, Universidad Diego Portales, Santiago, Chile, and Fabian Walter of the Max Planck Institute for Astronomy in Heidelberg, Germany, conducted a deeper search across about one sixth of the total HUDF [3].

We conducted the first fully blind, three-dimensional search for cool gas in the early Universe,” said Chris Carilli, an astronomer with the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, USA and member of the research team. “Through this, we discovered a population of galaxies that is not clearly evident in any other deep surveys of the sky.” [4]

Some of the new ALMA observations were specifically tailored to detect galaxies that are rich in carbon monoxide, indicating regions primed for star formation. Even though these molecular gas reservoirs give rise to the star formation activity in galaxies, they are often very hard to see with Hubble. ALMA can therefore reveal the “missing half” of the galaxy formation and evolution process.

“The new ALMA results imply a rapidly rising gas content in galaxies as we look back further in time,” adds lead author of two of the papers, Manuel Aravena (Núcleo de Astronomía, Universidad Diego Portales, Santiago, Chile). “This increasing gas content is likely the root cause for the remarkable increase in star formation rates during the peak epoch of galaxy formation, some 10 billion years ago.

The results presented today are just the start of a series of future observations to probe the distant Universe with ALMA. For example, a planned 150-hour observing campaign of the HUDF will further illuminate the star-forming potential history of the Universe.

By supplementing our understanding of this missing star-forming material, the forthcoming ALMA Large Program will complete our view of the galaxies in the iconic Hubble Ultra Deep Field,” concludes Fabian Walter.

Notes

[1] Astronomers specifically selected the area of study in the HUDF, a region of space in the faint southern constellation ofFornax (The Furnace), so ground-based telescopes in the southern hemisphere, like ALMA, could probe the region, expanding our knowledge about the very distant Universe.

Probing the deep, but optically invisible, Universe was one of the primary science goals for ALMA.

[2] In this context “high mass” means galaxies with stellar masses greater than 20 billion times that of the Sun ( 2 × 1010solar masses). For comparison, the Milky Way is a large galaxy and has a mass of around 100 billion solar masses.

[3] This region of sky is about seven hundred times smaller than the area of the disc of the full Moon as seen from Earth. One of the most startling aspects of the HUDF was the vast number of galaxies found in such a tiny fraction of the sky.

[4] ALMA’s ability to see a completely different portion of the electromagnetic spectrum from Hubble allows astronomers to study a different class of astronomical objects, such as massive star-forming clouds, as well as objects that are otherwise too faint to observe in visible light, but visible at millimetre wavelengths.

The search is referred to as “blind” as it was not focussed on any particular object.

The new ALMA observations of the HUDF include two distinct, yet complementary types of data: continuum observations, which reveal dust emission and star formation, and a spectral emission line survey, which looks at the cold molecular gas fueling star formation. The second survey is particularly valuable because it includes information about the degree to which light from distant objects has been redshifted by the expansion of the Universe. Greater redshift means that an object is further away and seen farther back in time. This allows astronomers to create a three-dimensional map of star-forming gas as it evolves over cosmic time.

Sitting For Long Periods of Time Is the Cause of 4% of Deaths Worldwide

Sitting For Long Periods of Time Is the Cause of 4% of Deaths Worldwide

Each year people go into September with a number of resolutions. Exercising and not spending so much time on the couch tend to be some of these good intentions. 31% of the worldwide population does not meet the current recommendations for physical activity according to several studies published in 2012 by the journal ‘Lancet’.

In addition, a lack of exercise is associated with major noncommunicable diseases and with deaths of any cause –inactivity is the culprit behind 6% to 9% of total worldwide deaths–.

Today’s lifestyle has an impact on these numbers. In fact, various studies over the last decade have demonstrated how the excessive amount of time we spend sitting down may increase the risk of death, regardless of whether or not we exercise.

A new study, published in the ‘American Journal of Preventive Medicine’ and in which San Jorge University in Zaragoza (Spain) participated, now estimates the proportion of deaths attributable to that ‘chair effect’ in the population of 54 countries, using data from 2002 to 2011.

“It is important to minimise sedentary behaviour in order to prevent premature deaths around the world,” Leandro Rezende, lead author of the study and a researcher at the University of Sao Paulo (Brazil), tells SINC. He also highlights that “cutting down on the amount of time we sit could increase life expectancy by 0.20 years in the countries analysed.”

The results reveal that over 60% of people worldwide spend more than three hours a day sitting down –the average in adults is 4.7 hours/day–, and this is the culprit behind 3.8% of deaths (approximately 433,000 deaths/year).

Among the territories studied, there were more deaths in the regions of the Western Pacific, followed by European countries, the Eastern Mediterranean, America and Southeast Asia.

The highest rates were found in Lebanon (11.6%), the Netherlands (7.6%) and Denmark (6.9%), while the lowest rates were in Mexico (0.6%), Myanmar (1.3%) and Bhutan (1.6%). Spain falls within the average range with 3.7% of deaths due to this ‘chair effect’.

More movement, fewer deaths

The authors calculate that reducing the amount of time we sit by about two hours (i.e., 50%) would mean a 2.3% decrease in mortality (three times less), although it is not possible to confirm whether this is a causal relationship.

Even a more modest reduction in sitting time, by 10% or half an hour per day, could have an immediate impact on all causes of mortality (0.6%) in the countries evaluated.

In the words of the experts, measures aimed at addressing the determining factors behind this sedentary conduct would be necessary. “Some examples of this approach were recently highlighted by the World Health Organization,” adds Rezende.

“For example, a strategic health communication campaign was developed to promote physical activity among women in Tonga (Oceania), while a bicycle-sharing system was developed in Iran in addition to a sustainable transport system in Germany,” he concludes.

The Death of A Planet Nursery?

The Death of A Planet Nursery?

The dusty disk surrounding the star TW Hydrae exhibits circular features that may signal the formation of protoplanets. LMU astrophysicist Barbara Ercolano argues, however, that the innermost actually points to the impending dispersal of the disk.

When the maps appeared at the end of March, experts were electrified. The images revealed an orange-red disk pitted with circular gaps that looked like the grooves in an old-fashioned long-playing record. But this was no throwback to the psychedelic Sixties. It was a detailed portrait of a so-called protoplanetary disk, made up of gas and dust grains, associated with a young star – the kind of structure out of which planets could be expected to form. Not only that, the maps showed that the disk around the star known as TW Hydrae exhibits several clearly defined gaps. Astronomers speculated that these gaps might indicate the presence of protoplanets, which had pushed away the material along their orbital paths. And to make the story even more seductive, one prominent gap is located at approximately the same distance from TW Hydrae as Earth is from the Sun – raising the possibility that this putative exoplanet could be an Earth-like one.

Now an international team led by Professor Barbara Ercolano at LMU’s Astronomical Observatory has compared the new observations with theoretical models of planet formation. The study indicates that the prominent gap in the TW Hydrae system is unlikely to be due to the action of an actively accreting protoplanet. Instead, the team attributes the feature to a process known as photoevaporation. Photoevaporation occurs when the intense radiation emitted by the parent star heats the gas, allowing it to fly away from the disk. But although hopes of a new exo-Earth orbiting in the inner gap of TW Hydrae may themselves have evaporated, the system nevertheless provides the opportunity to observe the dissipation of a circumstellar disk in unprecedented detail. The new findings appear in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

Only 175 light-years from Earth

The dusty disk that girdles TW Hydrae has long been a favored object of observation. The star lies only 175 light-years from Earth, and is it relatively young (around 106 years old). Moreover, the disk is oriented almost perpendicular to our line of sight, affording a well-nigh ideal view of its structure. The spectacular images released in March were made with the Atacama Large Millimeter/submillimeter Array (ALMA), an array of detectors in the desert of Northern Chile. Together, they form a radiotelescope with unparalleled resolving power that can detect the radiation from dust grains in the millimeter size range.

Photoevaporation is one of the major forces that shape the fate of circumstellar disks. Not only can it destroy such disks –which typically have a life expectancy of around 10 million years — it can also stop young planets being drawn by gravity and by the interaction with the surrounding disc gas into their parent star. The gaps caused by the action of photoevaporation on the disk, park the planets at their location by removing the gas, allowing the small dusty clumps to grow into fully fledged planets and steering them into stable orbits. However, in the case of the TW Hydrae system, Barbara Ercolano believes that the inner gap revealed by the ALMA maps is not caused by a planet, but represents an early stage in the dissipation of the disk. This view is based on the fact that many characteristic features of the disk around TW Hydrae, such as the distance between the gap and the star, the overall mass accretion rate, and the size and density distributions of the particles, are in very good agreement with the predictions of her photoevaporation model.

Reef Fish See Colors That Humans Cannot

Reef Fish See Colors That Humans Cannot

Researchers at The University of Queensland have established that reef fish see colours that humans cannot.

A team from Professor Justin Marshall’s Sensory Neurobiology Lab at the Queensland Brain Instituteran a series of behavioral experiments with trigger fish, in a bid to decode how they see the world.

Professor Marshall said previous studies had looked into how goldfish saw colour, but this was the first study into how reef fish discriminate colours.

“Coral reefs are the most colourful environments in the world, and it’s now become clear that reef fish see colours we can’t,” Professor Marshall said.

“Some reef fish, such as the anemonefish ‘Nemo’ and other damselfish can see the UV wavelengths we protect ourselves from.

“Triggerfish, on the other hand, see more or less the same colour range we do but their colour discriminations are different.

“Thinking about it, this is no big surprise. Their colour tasks are blue-biased, as they live in a blue ocean.

“Ironically, as the colours of the reef change and disappear because of climate change, we are just beginning to understand how reef inhabitants see and experience their vibrant world,” he said.

Professor Marshall said Dr Connor Champ led a series of detailed behavioural tests, where trigger fish were rewarded for discriminating against progressively similar colours.

It emerged that trigger fish see colours in some colour regions in more detail than humans.

“Many people ask me ‘Why study fish?’ and my first answer is: “Because I love them,” Professor Marshall said.

“But this sort of comparative look at animal systems is vitally important to understand not just the beauty of nature and how to look after it, but to consider the possible applications in the human world.”

Comparative colour vision research at QBI is helping in cancer detection, satellite design and data storage on computers.

The research, published in Royal Society Open Science, was funded by the Australian Research Council.

MRI Scanner Sees Emotions Flickering Across An Idle Mind

MRI Scanner Sees Emotions Flickering Across An Idle Mind

As you relax and let your mind drift aimlessly, you might remember a pleasant vacation, an angry confrontation in traffic or maybe the loss of a loved one.

And now a team of researchers at Duke University say they can see those various emotional states flickering across the human brain.

“It’s getting to be a bit like mind-reading,” said Kevin LaBar, a professor of psychology and neuroscience at Duke. “Earlier studies have shown that functional MRI can identify whether a person is thinking about a face or a house. Our study is the first to show that specific emotions like fear and anger can be decoded from these scans as well.”

A Duke team has mapped the distinct patterns of brain activity that correspond to seven different emotional states. The brain anatomy presented here is an average of data from 32 study subjects. Credit: Philip Kragel, Kevin LaBar, Duke University.

The data produced by a functional MRI hasn’t changed, but the group is applying new multivariate statistics to the scans of brain activity to see different emotions as networks of activity distributed across areas of the conscious and unconscious brain.

These networks were first mapped by the team in a March 2015 paper in the journal Social, Cognitive and Affective Neuroscience. They identified seven different patterns of brain activity reflecting contentment, amusement, surprise, fear, anger, sadness and neutrality.

To build these maps, they had put 32 research subjects into the scanner and exposed them to two music clips and two film clips that had been shown to induce each of the seven emotions. The subjects also completed self-report questionnaires on their mood states for further validation.

Analytical software called a machine learning algorithm was then presented with some of the subjects’ data and tasked with finding a pattern that concurred with each emotional stimulus. Having learned what each of the seven states ought to look like, the algorithm was then presented with the scans of the rest of the study group and asked to identify their emotional states without knowing which emotion prompt they received.

LaBar said the model performed better than chance at this task, despite differences in brain shapes and arousal levels between subjects. “And it proved fairly sensitive,” he said.

The latest study, appearing Sept. 14 in PLoS Biology, followed up by scanning 21 subjects who were not offered stimuli, but were encouraged to let their minds wander. Every thirty seconds, they responded to a questionnaire about their current emotional state.

“We tested whether these seven brain maps of emotions occurred spontaneously while participants were resting in the fMRI scanner without any emotional stimuli being presented,” LaBar said.

Data for the whole brain was collected every 2 seconds and each of these individual scans was compared to the seven patterns. The team examined the scanner data for the ten seconds previous to each self-report of mood, and found that the algorithm accurately predicted the moods the subjects self-reported.

LaBar said another source of validation is the indication that there’s a significant signal of anxiety at the beginning of each subjects’ data as they enter the confined, noisy MRI for the first time. “That’s what you’d expect to see for most people when they first enter the machine.”

In a second group of 499 subjects being scanned for the Duke Neurogenetics Study, the researchers had them rest in the scanner for nearly 9 minutes, and then asked them how depressed and anxious they felt after the scanning session. “We found that the cumulative presence of our ‘sad’ emotion map, summed over time, predicted their depression scores, and the cumulative presence of our ‘fear’ emotion map predicted their anxiety scores,” LaBar said.

This larger group was also tested for personality measures of depression, anxiety, and angry hostility. Again, the maps for depression and anxiety closely mirrored these measures. “We also showed that the cumulative presence of our ‘angry’ emotion map predicted individuals’ angry hostility traits,” LaBar said.

Aside from being an interesting proof of concept, LaBar thinks these new maps of emotional states could be useful in studying people who have poor insight into their emotional status, and might be used in clinical trials to test the effectiveness of treatments to regulate emotions.

LaBar says their conclusions about characteristic networks of brain areas governing emotional states also challenges prevailing theories about how emotions are formed. He adds that a Finnish team led by Lauri Nummenmaa has made similar maps of emotional networks from their brain scanning studies.

In further research, the Duke group will be pursuing a better understanding of the timing of emotional states and the transitions between them, as these may be relevant for understanding affective disorders.