quarta-feira, 30 de setembro de 2009
terça-feira, 29 de setembro de 2009
Caros amigos e amigas das árvores,
Até lá, agradecemos o envio de notícias sobre árvores para posterior divulgação na nossa página no Twitter: twitter.com/arvoresportugal
Por outro lado, a colaboração pode ser feita através da partilha de fotografias de árvores notáveis, utilizando o nosso grupo no : flickr.com/groups/arvoresdeportugal/
Por último, mas não menos importante, aguardamos a sua colaboração com o nosso blogue. sendo, caso o leitor possua uma história sobre a temática das árvores, não hesite e partilhe-a com todos os que amamos os gigantes dos nossos jardins e florestas. As suas contribuições serão apreciadas e poderão ser enviadas para a nossa página de contacto.
Por João Pires da Costa
segunda-feira, 28 de setembro de 2009
Investigador em astrobiologia e endosimbiose inauguram uma hipótese muito provável acerca da evolução da vida na Terra
Humans might not be walking on Earth today if not for the ancient fusing of two microscopic, single-celled organisms called prokaryotes, NASA-funded research has found.
By comparing proteins present in more than 3000 different prokaryotes – a type of single-celled organism without a nucleus – molecular biologist James A. Lake from the University of California at Los Angeles’ Center for Astrobiology showed that two major classes of relatively simple microbes fused together more than 2.5 billion years ago. Lake’s research reveals a new pathway for the evolution of life on Earth. These insights are published in the Aug. 20 online edition of the journal Nature.
This endosymbiosis, or merging of two cells, enabled the evolution of a highly stable and successful organism with the capacity to use energy from sunlight via photosynthesis. Further evolution led to photosynthetic organisms producing oxygen as a byproduct. The resulting oxygenation of Earth’s atmosphere profoundly affected the evolution of life, leading to more complex organisms that consumed oxygen, which were the ancestors of modern oxygen-breathing creatures including humans.
“Higher life would not have happened without this event,” Lake said. “These are very important organisms. At the time these two early prokaryotes were evolving, there was no oxygen in the Earth’s atmosphere. Humans could not live. No oxygen-breathing organisms could live.”
The genetic machinery and structural organization of these two organisms merged to produce a new class of prokaryotes, called double membrane prokaryotes. As they evolved, members of this double membrane class, called cyanobacteria, became the primary oxygen-producers on the planet, generating enough oxygen to alter the chemical composition of the atmosphere and set the stage for the evolution of more complex organisms such as animals and plants.
“This work is a major advance in our understanding of how a group of organisms came to be that learned to harness the sun and then effected the greatest environmental change Earth has ever seen, in this case with beneficial results,” said Carl Pilcher, director of the NASA Astrobiology Institute at NASA’s Ames Research Center in Moffett Field, Calif., which co-funded the study with the National Science Foundation in Arlington, Va.
Founded in 1998, the NASA Astrobiology Institute (NAI) is a partnership between NASA, 14 U.S. teams, and six international consortia. NAI’s goals are to promote, conduct, and lead interdisciplinary astrobiology research, train a new generation of astrobiology researchers, and share the excitement of astrobiology with learners of all ages. The Astrobiology Institute is part of NASA’s Astrobiology Program. The Astrobiology Program supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere.
domingo, 27 de setembro de 2009
porto from se cathedral. porto
360 cidades já aderiram e muitas mais numa rede crescente de serviços panorâmicos e experiências imersivas em paisagens e outros espaços, tudo confortavelmente no ecrã do teu computador!
Importância do turismo
sábado, 26 de setembro de 2009
sexta-feira, 25 de setembro de 2009
Ler o resto da notícia.
(retirado do DN, 2 de Janeiro de 2010) .
quinta-feira, 24 de setembro de 2009
Species are embedded in complex networks of relationships. Some more so than others. In those cases, a single extinction can cascade into the loss of many other species.Figuring this out in advance is supremely difficult. The number of links in even simple ecosystems exceeds the number of atoms in the universe. We can't sort out that kind of complexity without quantum computers.
But maybe Google can. Researchers Stefano Allesina and Mercedes Pascual reversed the definition of the PageRank algorithm that ranks a webpage as important if important pages point to it. In the conservation biology context, even humble species are important if they point to important species.
The researchers also designed a cyclical element into the foodweb system by including the detritus pool (you know, that to which all returns and that from which all arises).
Allesina and Pascual then tested their method against published foodwebs to rank species according to the damage caused if they were removed from the ecosystem. They also tested algorithms already in use in computational biology to find a solution to the same problem.The results: PageRank gave them exactly the same solution as the more complicated algorithms.In the real world, this research will likely make it easier to quickly target conservation efforts for maximum benefit.