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extinction

Rob Sheldon on the sixth great extinction

and others of note Further to: Is there a sixth great extinction in progress? (It would help if a key exponent was anyone but Paul “Population Bomb” Ehrlich, a contender for the heavyweight champ of wrong-headed predictions), at Evolution News & Views, Rob Sheldon offers While the criteria may sound quantitative, and the increase in extinction rate qualitatively higher, there is a missing factor in this calculation. First, the extinction rate in the past is determined from fossils. Since almost by definition, fossil animals are nearly all extinct today, the extinction rate is close to 100 percent. But the key thing is that not all species are represented in the fossil record. Second, the present extinction rate is determined from Read More ›

Is there a sixth great extinction in progress?

It would help if a key exponent was anyone but Paul “Population Bomb” Ehrlich, a contender for the heavyweight champ of wrong-headed predictions: “In real terms, we’re in trouble,” said Paul Ehrlich, a Stanford professor and president of the Center for Conservation Biology who co-authored the study. “This is another indicator that we are sawing off the limbs that we are sitting on.” Ehrlich and co-author Anthony Barnosky, a paleontologist at UC Berkeley, said extinctions thus far have been the result of overhunting and habitat destruction from overdevelopment, but climate change is likely to push things over the edge. Some of Ehrlich’s other predictions, courtesy Hot Air: So, let’s take a look at some of his predictions, made in 1968: Read More ›

So the Cambrian really was an explosion then?

The preceding Ediacaran life forms (635 to 542 mya) were gone already? Eaten up by early Cambrians (542 to 513 mya)? From New Scientist: The disappearance of the Ediacarans from the fossil record has long troubled biologists. Leading theories are a catastrophic mass extinction, that Ediacarans got eaten or had their habitat destroyed by newly evolved animals, or no longer left fossils because of a change in ocean conditions. But a careful search by Marc Laflamme of the University of Toronto in Mississauga and colleagues threw up no geochemical signatures of low-oxygen conditions or other turmoil to support the idea of an environmentally driven mass extinction. And given that soft-bodied Cambrian animals are fossilised within rocks like the famed Burgess Read More ›

Should the Big 5 extinction be considered the Big 6?

The Capitanian extinction, which did in a lot of brachiopods 262 mya From ScienceDaily: The widespread loss of carbonates across the Boreal Realm also suggests a role for acidification. The new data cements the Middle Permian crisis’s status as a true “mass extinction.” Thus the “Big 5” extinctions should now be considered the “Big 6.” More. Follow UD News at Twitter!

Would greater DNA harm enhance evolution or degradation?

Mutations are used to explain evolution but also cause cancer. Biologists have discovered conditions for multiple mutations. Can we therefore infer that evolution via mutations is more likely? or that enhanced mutations will cause faster species degradation and extinction?

Biologists describe mechanism promoting multiple DNA mutations

DNA mutations—long known to fuel cancer as well as evolutionary changes in a living organism—had been thought to be rare events that occur randomly throughout the genome.

However, recent studies have shown that cancer development frequently involves the formation of multiple mutations that arise simultaneously and in close proximity to each other. . . .Anna Malkova, associate professor of biology in the UI College of Liberal Arts and Sciences, notes that the DNA repair pathway, known as break-induced replication (BIR), can promote clusters of DNA mutations.

“Previously, we have shown that double-strand DNA breaks, which can result from oxidation, ionizing radiation and replication errors, can be repaired by BIR,” says Malkova.

“During BIR, one broken DNA end is paired with an identical DNA sequence on another chromosome and initiates an unusual type of replication, which proceeds as a migrating bubble and is associated with the accumulation of large amounts of single-strand DNA,” she says.

In the Cell Reports study, researchers subjected yeast cells undergoing BIR to alkylating (cancer cell-killing agents) damage. “We found that the single-stranded DNA regions that accumulate during BIR are susceptible to damage that leads to the formation of mutation clusters,” explains Cynthia Sakofsky, postdoctoral fellow at the UI and one of two co-first authors on the paper. “These clusters are similar to those found in human cancer,” she says.

Importantly, say the researchers, the paper provides a mechanism to potentially explain how genetic changes form in human cancers. Thus, it will be critical for future research to determine whether BIR can form clustered mutations that lead to cancer in humans.

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