Archives par mot-clé : Organisms

Dino-killing asteroid could have thrust Earth into two years of darkness

by National Center for Atmospheric Research/University Corporation for Atmospheric Research, August 21, 2017 in ScienceDaily

Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

The rise of algae in Cryogenian oceans and the emergence of animals

by Jochen J. Brocks et al., August 2017, in Nature

The ‘Rise of Algae’ created food webs with more efficient nutrient and energy transfers, driving ecosystems towards larger and increasingly complex organisms. This effect is recorded by the concomitant appearance of biomarkers for sponges and predatory rhizarians, and the subsequent radiation of eumetazoans in the Ediacaran period.

See also here

Abrupt summer sea ice decline has not affected polar bear numbers as predicted

by  Dr. Susan J. Crockford, July 14, 2017 in ClimateChangeDispatch

Yes, Arctic sea ice has declined since satellite records began in 1979 but polar bears have adjusted well to this change, especially to the abrupt decline to low summer sea ice levels that have been the norm since 2007. Some polar bear subpopulations have indeed spent more time on land in summer than in previous decades but this had little negative impact on health or survival and while polar bear attacks on humans appear to have increased in recent years (Wilder et al. 2017), the reasons for this are not clear: reduced summer sea ice is almost certainly not the causal factor (see previous post here).

Why there are so many species of tropical trees and other organisms

by Washington University in St-Louis, June 29, 2017 in ScienceDaily

If aliens sent an exploratory mission to Earth, one of the first things they’d notice — after the fluffy white clouds and blue oceans of our water world — would be the way vegetation grades from exuberance at the equator through moderation at mid-latitudes toward monotony at higher ones. We all learn about this biodiversity gradient in school, but why does it exist?