Psychology & Psychiatry

Sleep loss hijacks brain's activity during learning

Sleep is crucial for consolidating our memories, and sleep deprivation has long been known to interfere with learning and memory. Now a new study shows that getting only half a night's sleep—as many medical workers and ...

Neuroscience

With these neurons, extinguishing fear is its own reward

When you expect a really bad experience to happen and then it doesn't, it's a distinctly positive feeling. A new study of fear extinction training in mice may suggest why: The findings not only identify the exact population ...

Psychology & Psychiatry

Mindfulness makes it easier to forget your fears

Mindfulness has previously been shown to help people handle negative emotions and is used as a treatment for anxiety related psychological disorders, but the underlying biological mechanisms are not fully understood. In a ...

Psychology & Psychiatry

How cortisol affects exposure therapy for anxiety disorders

Bochum-based psychologists have studied how the application of the stress hormone cortisol affects exposure therapy for anxiety disorders. The researchers knew from earlier studies that extinction learning, which constitutes ...

page 1 from 5

Extinction

In biology and ecology, extinction is the end of a species or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "re-appears" (typically in the fossil record) after a period of apparent absence.

Through evolution, new species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive virtually unchanged for hundreds of millions of years. Extinction, though, is usually a natural phenomenon; it is estimated that 99.9% of all species that have ever lived are now extinct.

Prior to the dispersion of humans across the earth, extinction generally occurred at a continuous low rate, mass extinctions being relatively rare events. Starting approximately 100,000 years ago, and coinciding with an increase in the numbers and range of humans, species extinctions have increased to a rate unprecedented since the Cretaceous–Tertiary extinction event. This is known as the Holocene extinction event and is at least the sixth such extinction event. Some experts have estimated that up to half of presently existing species may become extinct by 2100.

This text uses material from Wikipedia, licensed under CC BY-SA