GLAND, Switzerland, May 16 (UPI) -- The WWF, also known as the World Wildlife Fund, says more than a quarter of the Earth's wildlife has been lost during the last 35 years.

The organization's Living Planet Index -- produced for the WWF by the Zoological Society of London -- shows populations of marine species, such as swordfish and scalloped hammerhead, were particularly hard hit, falling by 28 percent between 1995 and 2005. Seabird populations have suffered a 30 percent decline since the mid-1990s.

The index said land-based species' populations fell by 25 percent between 1970 and 2005, and populations of freshwater species by 29 percent between 1970 and 2003.

Scientists said habitat destruction and wildlife trade were among the major causes of population declines but climate change is expected to become an increasingly important factor.

"No one can escape the impact of biodiversity loss," said James Leape, WWF's director general, "because reduced global diversity translates quite clearly into fewer new medicines, greater vulnerability to natural disasters and greater effects from global warming."

Cell cancer-fighting trigger is found

SASKATOON, Saskatchewan, May 16 (UPI) -- A Canadian scientist says he's found a way to trigger a protein that causes cells to fight cancer-causing agents, such as ultraviolet radiation.

University of Saskatchewan microbiology Professor Wei Xiao discovered how to trigger the protein combination called 9-1-1 in a finding that's been called a breakthrough in cancer research that could possibly lead to better cancer diagnosis through targeting defective genes.

Xiao and a team of graduate students found a process that can be used to activate the 9-1-1 protein complex, warning cells to stop dividing with damaged DNA that leads to cancer.

"It has been known for many years that 9-1-1 was important, but scientists did not know how it was turned on," said Xiao."We figured out how 9-1-1 is actually activated when cells face carcinogens."

The next step toward developing diagnostic tools and drug treatments is to test whether Xiao's model, which used genes from baker's yeast that have counterparts in people, can apply to human cells as well.

The study appears in the journal Cell and will be presented this summer at Britain's Oxford University during the Gordon Research Conference on Mutagenesis.

Interior of Mars is colder than thought

PASADENA, Calif., May 16 (UPI) -- New data from the U.S. space agency's Mars Reconnaissance Orbiter suggest the crust and upper mantle of Mars is stiffer and colder than thought.

National Aeronautics and Space Administration scientists said the findings suggest any liquid water existing beneath that planet's surface -- and any possible organisms in the water -- would be located deeper than scientists had suspected.

"We found that the rocky surface of Mars is not bending under the load of the north polar ice cap," said Roger Phillips of the Southwest Research Institute in Boulder, Colo. "This implies that the planet's interior is more rigid, and thus colder, than we thought before."

Scientists at NASA's Jet Propulsion Laboratory, which manages the Orbiter mission, said radar images show a smooth, flat border between the ice cap and the rocky Martian crust. On Earth, the weight of a similar amount of ice would cause the planet's surface to sag. The fact the Martian surface is not bending means its strong outer shell -- or lithosphere, a combination of its crust and upper mantle -- must be very thick and cold, they said.

The findings are reported in the online version of the journal Science.

Study shows bird sight isn't human sight

UPPSALA, Sweden, May 16 (UPI) -- Swedish researchers say they've found a bird's visual perception is very different from that of a human, suggesting a re-evaluation of many studies.

Anders Odeen and Olle Hastad of Uppsala University conducted experiments showing that what birds see isn't what humans see. They note that many studies about factors influencing avian sexual selection incorrectly assume birds see what we see.

"The results mean that many studies on sexual selection may need to be re-evaluated," said Odeen.

The researchers used mathematical models of the retina in birds and humans. The models used information on differences in the color-sensitive cone cells of the eye to determine how the richness and brightness of colors are perceived by birds and humans.

Birds' eyes, the scientists discovered, have four types of color-sensitive cones, while those of humans have three. Birds can also perceive ultraviolet light, whereas humans cannot.

The models were used to evaluate how birds and humans perceive different visual arrays set up by the experimenters. The researchers said their results show colors are perceived differently by birds and humans more than 39 percent of the time.

The study appears in the journal American Naturalist.