2011 Science News of the Year: Life
Multicellular life from a test tube
In less than two months, yeast in a test tube evolved from single-celled life to bristly multicellular structures. The new, snowflakelike forms act like multicellular organisms, reproducing by splitting when they reach large sizes and evolving further in response to harsh conditions, William Ratcliff of the University of Minnesota, Twin Cities reported in Norman, Okla., at the Evolution 2011 meeting (SN: 7/16/11, p. 11).
To create pressure to evolve in the experiment, Ratcliff and his colleagues subjected tubes of yeast in liquid to a daily ordeal: a mild spin in a centrifuge and then removal of all but the sludge with the heaviest yeast. Yeasts reproduce by budding, and cells that continued clinging to their daughter buds after cell division probably landed in the sludge and survived. Under pressure from these daily tosses, yeast lineages started holding onto buds that had themselves budded, creating multicelled spiky shapes.
Additional data revealed that the snowflakes amount to more than one-celled microbes known to cluster or form films, suggesting that multicellularity may arise more readily than previously thought, the researchers argue. —Susan Milius
Daniel J. Cox/Naturalexposures.com
Irish bears DNA analysis suggests that all of today’s polar bears can trace their maternal ancestry to a female brown bear in Ireland. Polar bears interbred with brown bears in or near Ireland between 20,000 and 50,000 years ago (SN: 7/30/11, p. 5).
Unexpected farmers A social amoeba, Dictyostelium discoideum, practices simple agriculture in the form of bacterial husbandry (SN: 2/12/11, p. 11).
Gone fishing Orangutans in Borneo dine on stranded fish, occasionally jabbing at them with sticks to get them to flop out of the water (SN: 5/7/11, p. 16).
Elephants divided A genetic analysis of elephants and their extinct relatives shows that forest-dwelling African elephants are a separate species from Africa’s savanna elephants (SN: 1/15/11, p. 16).
Eyespots have it Research reveals that more peacock eyespots might not always win a mate, but peahens appear to expect a threshold number before they are willing to get their game on (SN: 5/21/11, p. 10).
Cycad rewrite Today’s cycads, once touted as survivors from dinosaur times, turn out to be mostly recent species, diversifying from an ancestor that flourished around 12 million years ago (SN Online: 10/21/11).
Baboon boss stress Top-ranking male baboons generate surprisingly high levels of stress hormones, a sign that these primates pay a cost to be the boss (SN: 8/13/11, p. 11).
Fungus killer A systematic test with initially healthy little brown bats shows that the fungus Geomyces destructans is the primary cause of white-nose syndrome (SN: 12/3/11, p. 12).
Plant rewards In one of the biggest underground markets on the planet — nutrient trading between plant roots and fungi — good suppliers get rewards and bad ones get less business, researchers find (SN: 9/10/11, p. 15).
Diving spiders The air bubbles carried by Eurasian diving bell spiders can act as physical gills, pulling oxygen from the water (SN: 7/2/11, p. 14).
Connecticut cat A cougar took a 2,000-mile journey from the Black Hills of South Dakota to the green lawns of southern New England (SN: 8/27/11, p. 5).
Mice boom A syndrome that has wiped out swaths of aspens across the western United States is linked to an increase in disease-carrying deer mice (SN: 1/29/11, p. 15).
Evolutionary dawdling The last common ancestor of all living animals probably arose nearly 800 million years ago, scientists report — suggesting animals started evolving roughly 200 million years before what’s known as the Cambrian Explosion (SN: 12/31/11, p. 12).
Electric sensibilities The dolphin is the first true mammal found to detect electrical fields, via organs thought to be long-lost whiskers (SN: 8/27/11, p. 12).
Stress goes on Not only do zebra finch nestlings dosed with stress hormones tend to die early, but the nestlings also pass the risk of a shortened life span on to future long-term mating partners (SN: 9/24/11, p. 14).
Engineered release Lab mosquitoes infected with a bacterium that renders them unlikely to pass along dengue mate well enough with wild populations to make the bacteria widespread, field tests in towns in Australia reveal (SN Online: 8/24/11).