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Scientists Estimate Earth Is Home to One Trillion Microbial Species

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Lift your pinkies and summon your hairless cats, because it’s time to get a little Doctor Evil: researchers say Earth may currently support one TRILLION different microbe species. They published their report in the Proceedings of the National Academy of Sciences. 

This may seem like a strange pronouncement. After all, shouldn’t we already know how many species are sharing our home planet? Well, no. We can’t even agree on a standardized definition of the term “species.” And, well, microorganisms are very, very small. For most of human existence, we didn’t even know they were here.

So making an educated guess about the number of species has been kind of tricky. That hasn’t stopped scientists from doing it, of course, but they’ve always been limited by the technology available. 

To create a more up-to-date estimate, scientists collected data from 20,376 reports on bacteria, archaea (single-celled organisms), and microscopic fungi, and another 14,862 on populations of trees, birds, and mammals. In total, the dataset incorporated information about more than 5.6 million species from 35,000 locations in all the world's oceans and on every continent but Antarctica. 

Kenneth Locey is an ecologist at Indiana University (IU) and co-author of the study. "A massive amount of data has been collected from these surveys," Locey said in a press statement. "Yet few have tried to pull together all the data to test big questions."

The laws of scaling are a set of scientific principles that explain how various natural elements like habitat area and population size are related. But scientists were previously unsure if biodiversity fit within those laws—that is, if it were scaleable. 

The results of this study suggest that it is scaleable, and in a major way. “After analyzing a massive amount of data,” Locey said, “we observed simple but powerful trends in how biodiversity changes across scales of abundance."

Species abundance, they found, has a very strong relationship with the number of individuals. In other words, the more ants there are, the more ant species there are likely to be. Locey said biodiversity may be “the most expansive scaling law in biology.” 

The researchers were then able to apply what they knew about existing species and biodiversity to build an estimate of the number of microbe species on Earth. That number? One trillion. 

"Before high-throughput genetic sequencing,” said IU microbe diversity expert and co-author Jay Lennon, “scientists characterized diversity based on 100 individuals, when we know that a gram of soil contains up to a billion organisms, and the total number on Earth is more than 20 orders of magnitude greater.” 

But just because we know they’re out there doesn’t mean they’ll be easy to find or identify. “Of those species cataloged, only about 10,000 have ever been grown in a lab, and fewer than 100,000 have classified genetic sequences," Lennon said. "Our results show that this leaves 100,000 times more microorganisms awaiting discoveryand 100 million to be fully explored." 

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People Listen (and Remember) Better With Their Right Ears, Study Finds
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If you’re having trouble hearing in a noisy situation, you might want to turn your head. New research finds that people of all ages depend more on their right ear than their left, and remember information better if it comes through their right ear. The findings were presented at the annual meeting of the Acoustical Society of America in New Orleans on December 6.

Kids’ ears work differently than adults' do. Previous studies have found that children's auditory systems can’t separate and process information coming through both of their ears at the same time, and rely more on the auditory pathway coming from the right. This reliance on the right ear tends to decrease when kids reach their teens, but the findings suggest that in certain situations, right-ear dominance persists long into adulthood.

To study how we process information through both our ears, Auburn University audiologists brought 41 adult subjects (between the ages of 19 and 28) into the lab to complete dichotic listening tests, which involve listening to different auditory inputs in each ear. They were either supposed to pay attention only to the words, sentences, or numbers they heard in one ear while ignoring the other, or they were asked to repeat all the words they heard in both ears. In this case, the researchers slowly upped the number of items the test subjects were asked to remember during each hearing test.

Instructions for the audio test read 'Repeat back only the numbers you hear in the right ear.'
Sacchinelli, Weaver, Wilson and Cannon - Auburn University

They found that the harder the memory tests got, the more performance varied between the ears. While both ears performed equally when people were asked to remember only four or so words, when the number got higher, the difference between their abilities became more apparent. When asked to only focus on information coming through their right ear, people’s performance on the memory task increased by an average of 8 percent. For some people, the result was even more dramatic—one person performed 40 percent better while listening with only their right ear.

"Conventional research shows that right-ear advantage diminishes around age 13, but our results indicate this is related to the demand of the task,” one of the researchers, assistant professor Aurora Weaver, explained in a press release. In other words, when the going gets tough, the right ear steps up.

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Pigeons Are Secretly Brilliant Birds That Understand Space and Time, Study Finds
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Of all the birds in the world, the pigeon draws the most ire. Despite their reputation as brainless “rats with wings,” though, they’re actually pretty brilliant (and beautiful) animals. A new study adds more evidence that the family of birds known as pigeons are some of the smartest birds around, as Quartz alerts us.

In addition to being able to distinguish English vocabulary from nonsense words, spot cancer, and tell a Monet from a Picasso, pigeons can understand abstract concepts like space and time, according to the new study published in Current Biology. Their brains just do it in a slightly different way than humans’ do.

Researchers at the University of Iowa set up an experiment where they showed pigeons a computer screen featuring a static horizontal line. The birds were supposed to evaluate the length of the line (either 6 centimeters or 24 centimeters) or the amount of time they saw it (either 2 or 8 seconds). The birds perceived "the longer lines to have longer duration, and lines longer in duration to also be longer in length," according to a press release. This suggests that the concepts are processed in the same region of the brain—as they are in the brains of humans and other primates.

But that abstract thinking doesn’t occur in the same way in bird brains as it does in ours. In humans, perceiving space and time is linked to a region of the brain called the parietal cortex, which the pigeon brains lack entirely. So their brains have to have some other way of processing the concepts.

The study didn’t determine how, exactly, pigeons achieve this cognitive feat, but it’s clear that some other aspect of the central nervous system must be controlling it. That also opens up the possibility that other non-mammal animals can perceive space and time, too, expanding how we think of other animals’ cognitive capabilities.

[h/t Quartz]

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