Monday, August 16, 2010

TINY FISH EVOLVED TO TOLERATE COLDER TEMPERATURE IN THREE YEARS

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University of British Columbia researchers have observed one of the fastest evolutionary responses ever recorded in wild populations. In as little as three years, stickleback fish developed tolerance for water temperature 2.5 degrees Celsius lower than their ancestors.

The study, published in the current issue of the Proceedings of the Royal Society B, provides the some of the first experimental evidence that evolution may help populations survive effects of climate change.

Measuring three to 10 centimetres, stickleback fish originated in the ocean but began populating freshwater lakes and streams following the last ice age. Over the past 10,000 years, marine and freshwater sticklebacks have evolved different physical and behavioural traits, making them ideal models for Darwin’s natural selection theory.

“By testing the temperature tolerance of wild and lab-raised sticklebacks, we were able to determine that freshwater sticklebacks can tolerate lower temperatures than their marine counterparts,” says lead author Rowan Barrett from the UBC Department of Zoology. “This made sense from an evolutionary perspective because their ancestors were able to adapt to freshwater lakes, which typically reach colder temperatures than the ocean.”

To learn how quickly this adaptation took place, Barrett and colleagues from Switzerland and Sweden “recreated history” by transplanting marine sticklebacks to freshwater ponds and found that in as little as three generations (or three years), they were able to tolerate the same minimum temperature as freshwater sticklebacks, 2.5 °C lower than their ancestral populations.

“Scientific models have suggested that climate change could result in both a general, gradual increase of average temperatures and an increase in extreme temperatures,” says Barrett.

“Our study is the first to experimentally show that certain species in the wild could adapt to climate change very rapidly – in this case, colder water temperature. However, this rapid adaptation is not achieved without a cost. Only rare individuals that possess the ability to tolerate rapid changes in temperature survive, and the number of survivors may not be large enough to sustain the population. It is crucial that knowledge of evolutionary processes is incorporated into conservation and management policy.”

(Photo: Rowan Barrett, UBC)

University of British Columbia

ANCIENT BLOB-LIKE CREATURE OF THE DEEP REVEALED BY SCIENTISTS

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A unique blob-like creature that lived in the ocean approximately 425 million years ago is revealed in a 3D computer model in research published today in the journal Biology Letters. The model is helping researchers to understand what primitive species on early Earth looked like and how they might have evolved into the types of creatures that are on Earth today.

The scientists, from Imperial College London, have developed a detailed 3D model of the only known fossilised specimen in the world of a creature called Drakozoon. The specimen was found by one of the team approximately 6 years ago in the Herefordshire Lagerstätte, one of England's richest deposits of soft-bodied fossils.

Drakozoon lived in the ocean during the Silurian Period, 444 to 416 million years ago, and today's model hints at how it lived.

The research reveals that Drakozoon was a cone-shaped, blob-like creature with a hood and it probably had a leathery exterior skin. It appears to have survived in the ocean by attaching itself to hard surfaces such as rock. It was approximately 3mm long, and used filament-bearing tentacles to catch and eat organic particles in seawater. It pulled its hood down over its body for protection against predators, pulling it back again to expose its tentacles when danger passed.

Dr Mark Sutton, from the Department of Earth Science and Engineering at Imperial College London, says:

"Excitingly, our 3D model brings back to life a creature that until recently no one knew even existed, and provides us with a window into the life of Drakozoon. We think this tiny blob of jelly survived by clinging onto rocks and hard shelled creatures, making a living by plucking microscopic morsels out of seawater. By looking at this primitive creature, we also get one tantalising step closer to understanding what the earliest creatures on Earth looked like."

Scientists have debated what the first relatives of all creatures on Earth may have resembled and how their bodies evolved. Some scientists think the creatures had repeated units, similar to a caterpillar with its many segments and legs, while others think that their bodies were structured in more free-form ways, similar to slugs.

In today's study, the researchers analysed their 3D model and discovered that Drakozoon had eight deep ridges on either side of its body. They suggest that these deep ridges are the genetic remnants from a time when Drakozoon had a body made of repeated units, supporting the theory that the earliest creatures on Earth were also made of repeated units.

The study shows that Drakozoon was an early member of a major group of invertebrate species called lophophorates. The best known lophophorates are the brachiopods, a type of spineless shellfish that are some of the most common fossils from the Silurian Period. The team found their Drakozoon specimen clinging onto the fossilised shell of a brachiopod.

The researchers created their 3D model by physically slicing a fossil into 200 pieces. These pieces were individually photographed and the images were fed into a computer, which generated the 3D model for analysis by the scientists.

The researchers say it is very rare to find ancient soft bodied creatures intact because they normally decompose before they can be preserved in sediment. The soft bodied Drakozoon was perfectly preserved because it lived in an area that was covered in volcanic ash, following a volcanic eruption that instantly entombed it and other creatures living with it, keeping it intact for 425 million years.

(Photo: ICL)

Imperial College London

TRAVELING BY CAR INCREASES GLOBAL TEMPERATURES MORE THAN BY PLANE, BUT ONLY IN LONG TERM

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Driving a car increases global temperatures in the long run more than making the same long-distance journey by air according to a new study. However, in the short run travelling by air has a larger adverse climate impact because airplanes strongly affect short-lived warming processes at high altitudes. The study appears in ACS' Environmental Science & Technology, a semi-weekly journal.

In the study, Jens Borken-Kleefeld and colleagues compare the impacts on global warming of different means of transport. The researchers use, for the first time, a suite of climate chemistry models to consider the climate effects of all long- and short-lived gases, aerosols and cloud effects, not just carbon dioxide, resulting from transport worldwide. They concluded that in the long run the global temperature increase from a car trip will be on average higher than from a plane journey of the same distance. However, in the first years after the journey, air travel increases global temperatures four times more than car travel. Passenger trains and buses cause four to five times less impact than automobile travel for every mile a passenger travels. The findings prove robust despite the scientific uncertainties in understanding the earth's climate system.

"As planes fly at high altitudes, their impact on ozone and clouds is disproportionately high, though short lived. Although the exact magnitude is uncertain, the net effect is a strong, short-term, temperature increase," explains Dr. Jens Borken-Kleefeld, lead author of the study. "Car travel emits more carbon dioxide than air travel per passenger mile. As carbon dioxide remains in the atmosphere longer than the other gases, cars have a more harmful impact on climate change in the long term."

ACS Publications

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