суббота, 18 января 2020 г.

Scientists uncover how an explosion of new genes explain the origin of land plants

The new study, led by scientists from the universities of Bristol and Essex and published in Current Biology, challenge the established view of the origin of plants on land, and reveal that compared to the origin of animals, plants are better at inventing new genes during periods of evolution.

Scientists uncover how an explosion of new genes explain the origin of land plants
Credit: Stock Photos
Plants constitute one of the major lineages of life and are the basis of almost all ecosystems, being an important source of food and oxygen. During evolution, all organisms gain new genes, lose old ones, or simply recycle genes.

The research team set out to understand which changes, at the genetic level, took place during the evolutionary transition of plants by comparing over 200 genomes, one of the largest datasets ever assembled to tackle the evolution of the plant kingdom.

Using sophisticated computer techniques enabled the researchers to essentially travel back in time 470 million years ago to find out which genes were present in the first land-based plants as they evolved from living in water to land.

Dr Jordi Paps, Lecturer from Bristol's School of Biological Sciences and lead researcher, explained: "After comparing over 200 genomes of the plant kingdom, we discovered that the origin of land plants is associated with two explosions of new genes, an unprecedented level of genomic novelty. Our findings challenge previous views of this transition being more gradual at genetic level.

"The first burst predates the origin of land plants, before they left their aquatic environments, and comprises genes that explain why plants are multicellular. The second coincides with the origin of land plants, and involved genes related to adaptations to challenges found in terrestrial environments."

The team now plans to use the same approach to identify drought-resistant genes in crops.

Dr Paps added: "We now plan to use the same approach to further explore the genes involved in drought tolerance. Most crops are sensitive to drought conditions, using our methods we can find genes involved in drought resistance that we can potentially introduce in dessication-sensitive plants."

Source: University of Bristol [January 16, 2020]

* This article was originally published here

Old Sarum Salisbury

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Old Sarum is the site of the earliest settlement of Salisbury in England. Located on a hill about 2 miles north of modern Salisbury near the A345 road, the settlement appears in some of the earliest records in the country.
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The mysterious, legendary giant squid's genome is revealed

How did the monstrous giant squid -- reaching school-bus size, with eyes as big as dinner plates and tentacles that can snatch prey 10 yards away -- get so scarily big?

The mysterious, legendary giant squid's genome is revealed
The giant squid has long been a subject of horror lore. In this original illustration from
Jules Verne's '20,000 Leagues Under the Sea,' a giant squid grasps a helpless sailor
[Credit: Alphonse de Neuville]
Today, important clues about the anatomy and evolution of the mysterious giant squid (Architeuthis dux) are revealed through publication of its full genome sequence by a University of Copenhagen-led team that includes scientist Caroline Albertin of the Marine Biological Laboratory (MBL), Woods Hole.

Giant squid are rarely sighted and have never been caught and kept alive, meaning their biology (even how they reproduce) is still largely a mystery. The genome sequence can provide important insight.

"In terms of their genes, we found the giant squid look a lot like other animals. This means we can study these truly bizarre animals to learn more about ourselves," says Albertin, who in 2015 led the team that sequenced the first genome of a cephalopod (the group that includes squid, octopus, cuttlefish, and nautilus).

Led by Rute da Fonseca at University of Copenhagen, the team discovered that the giant squid genome is big: with an estimated 2.7 billion DNA base pairs, it's about 90 percent the size of the human genome.

The mysterious, legendary giant squid's genome is revealed
These are giant squid sucker rings [Credit: The Trustees of the Natural History Museum, London]
Albertin analyzed several ancient, well-known gene families in the giant squid, drawing comparisons with the four other cephalopod species that have been sequenced and with the human genome.

She found that important developmental genes in almost all animals (Hox and Wnt) were present in single copies only in the giant squid genome. That means this gigantic, invertebrate creature -- long a source of sea-monster lore -- did NOT get so big through whole-genome duplication, a strategy that evolution took long ago to increase the size of vertebrates. So, knowing how this squid species got so giant awaits further probing of its genome.

"A genome is a first step for answering a lot of questions about the biology of these very weird animals," Albertin said, such as how they acquired the largest brain among the invertebrates, their sophisticated behaviors and agility, and their incredible skill at instantaneous camouflage.

The mysterious, legendary giant squid's genome is revealed
Left: Giant squid specimen kept at the Darwin Center Tank Room at the Natural History Museum, London. Right: The same
individual being measured prior to fixation [Credit: The Trustees of the Natural History Museum, London]
"While cephalopods have many complex and elaborate features, they are thought to have evolved independently of the vertebrates. By comparing their genomes we can ask, 'Are cephalopods and vertebrates built the same way or are they built differently?'" Albertin says.

Albertin also identified more than 100 genes in the protocadherin family -- typically not found in abundance in invertebrates -- in the giant squid genome.

"Protocadherins are thought to be important in wiring up a complicated brain correctly," she says. "They were thought they were a vertebrate innovation, so we were really surprised when we found more than 100 of them in the octopus genome (in 2015). That seemed like a smoking gun to how you make a complicated brain. And we have found a similar expansion of protocadherins in the giant squid, as well."

The mysterious, legendary giant squid's genome is revealed
Scale of size between human and giant squid [Credit: University of Copenhagen]
Lastly, she analyzed a gene family that (so far) is unique to cephalopods, called reflectins. "Reflectins encode a protein that is involved in making iridescence. Color is an important part of camouflage, so we are trying to understand what this gene family is doing and how it works," Albertin says.

"Having this giant squid genome is an important node in helping us understand what makes a cephalopod a cephalopod. And it also can help us understand how new and novel genes arise in evolution and development."

Author: Diana Kenney | Source: Marine Biological Laboratory [January 16, 2020]

* This article was originally published here

Spot The Police Car

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Category: Education

'Living fossil' may upend basic tenet of evolutionary theory

The field of evolutionary biology has seen its share of spirited debates. But if there's one principle that virtually every expert in the field agrees on, it's that natural selection occurs at the level of the genome.

'Living fossil' may upend basic tenet of evolutionary theory
Cryptococcus neoformans [Credit: © Kateryna_Kon/Adobe Stock]
But now, a UC San Francisco-led research team has discovered the first conclusive evidence that selection may also occur at the level of the epigenome -- a term that refers to an assortment of chemical "annotations" to the genome that determine whether, when and to what extent genes are activated -- and has done so for tens of millions of years. This unprecedented finding subverts the widely accepted notion that over geologic timescales, natural selection acts exclusively on variation in the genome sequence itself.

In a study published in the journal Cell, the researchers show that Cryptococcus neoformans -- a pathogenic yeast that infects people with weakened immune systems and is responsible for about 20 percent of all HIV/AIDS-related deaths -- contains a particular epigenetic "mark" on its DNA sequence, which, based on their lab experiments and statistical models, should have disappeared from the species sometime during the age of the dinosaurs.

But the study shows that this methylation mark -- so named because it's created through a process that attaches a molecular tag called a methyl group to the genome -- has managed to stick around for at least 50 million years -- maybe as long as 150 million years -- past its predicted expiration date. This amazing feat of evolutionary tenacity is made possible by an unusual enzyme and a hefty dose of natural selection.

"What we've seen is that methylation can undergo natural variation and can be selected for over million-year time scales to drive evolution," explained Hiten Madhani, MD, PhD, professor of biochemistry and biophysics at UCSF and senior author of the new study. "This is a previously unappreciated mode of evolution that's not based on changes in the organism's DNA sequence."

Though not seen in all life forms, DNA methylation isn't uncommon either. It's found in all vertebrates and plants, as well as many fungi and insects. In some species, however, methylation is nowhere to be found.

"Methylation has a patchy evolutionary presence," said Madhani, who is also a member of the UCSF Helen Diller Family Comprehensive Cancer Center and a Chan-Zuckerberg Biohub investigator. "Depending on what branch of the evolutionary tree you look at, different epigenetic mechanisms have been maintained or not maintained."

Many model organisms that are staples of the modern molecular biology lab -- including the baker's yeast S. cerevisiae, the roundworm C. elegans, and the fruit fly D. melanogaster -- lack DNA methylation entirely. These species are descended from ancient ancestors that lost enzymes that were, until this study was published, thought to be essential for propagating methylation for generation upon generation. How C. neoformans managed to avoid the same fate was a mystery up to now.

In the new study, Madhani and his collaborators show that hundreds of millions of years ago, the ancestor of C. neoformans had two enzymes that controlled DNA methylation. One was what's known as a "de novo methyltransferase," which was responsible for adding methylation marks to "naked" DNA that had none. The other was a "maintenance methyltransferase" that functioned a bit like a molecular Xerox. This enzyme copied existing methylation marks, which had been put in place by the de novo methyltransferase, onto unmethylated DNA during DNA replication. And like every other species with an epigenome that includes methylation, the ancestor of C. neoformans had both types of methyltransferase.

But then, sometime during the age of the dinosaurs, the ancestor of C. neoformans lost its de novo enzyme. Its descendants have been living without one since then, making C. neoformans and its closest relatives the only species alive today known to have DNA methylation without a de novo methyltransferase. "We didn't understand how methylation could still be in place since the Cretaceous period without a de novo enzyme," said Madhani.

Though the maintenance methyltransferase was still available to copy any existing methylation marks -- and the new study clearly demonstrates that this enzyme is unique among such enzymes for a number of reasons, including its ability to propagate existing methylation marks with exceptionally high fidelity -- the study also shows that unless natural selection were acting to preserve methylation, the ancient loss of the de novo methyltransferase should have resulted in the rapid demise and eventual disappearance of DNA methylation in C. neoformans.

That's because methylation marks can be randomly lost, which means that no matter how exquisitely a maintenance methyltransferase copies existing marks onto new strands of DNA, the accumulated loss of methylation would eventually leave the maintenance enzyme with no template to work from. Though it's conceivable that these loss events might occur at a sluggish pace, experimental observations allowed the researchers to determine that each methylation mark in C. neoformans was likely to disappear from half of the population after just 7500 generations. Even assuming that for some reason C. neoformans might reproduce 100 times more slowly in the wild than in the lab, this would still be the equivalent of only 130 years.

The rare and random acquisition of new methylation marks can't account for the persistence of methylation in C. neoformans either. The researchers' lab experiments demonstrated that new methylation marks arise by chance at a rate 20 times slower than methylation losses. Over evolutionary timescales, the losses would clearly predominate, and without a de novo enzyme to compensate, methylation would have vanished from C. neoformans around the time when dinosaurs disappeared had it not been for selection pressures favoring the marks.

In fact, when the researchers compared a variety of C. neoformans strains that were known to have diverged from one another nearly 5 million years ago, they found that not only did all the strains still have DNA methylation, but the methylation marks were coating analogous regions of the genome, a finding which suggests that methylation marks at specific genomic sites confer some sort of survival advantage that's being selected for.

"Natural selection is maintaining methylation at much higher levels than would be expected from a neutral process of random gains and losses. This is the epigenetic equivalent of Darwinian evolution," said Madhani.

Asked why evolution would select for these particular marks, Madhani explained that "one of methylation's major functions is genome defense. In this case we think it's for silencing transposons."

Transposons, also known as jumping genes, are stretches of DNA that are able to extract themselves from one part of the genome and insert themselves into another. If a transposon were to insert itself into the middle of a gene needed for survival, that gene may no longer function and the cell would die. Therefore, transposon-silencing methylation provides an obvious survival advantage, which is exactly what's needed to drive evolution.

However, it remains to be seen how common this unappreciated form of natural selection is in other species.

"Previously, there was no evidence of this kind of selection happening over these time scales. This is an entirely novel concept," Madhani said. "But now the big question is 'Is this happening outside of this exceptional circumstance, and if so, how do we find it?'"

Author: Jason Alvarez | Source: University of California - San Francisco [January 16, 2020]

* This article was originally published here

United States Air Force Upper Heyford Part 2

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Home to the US nuclear bombers which kept Western Europe safe from Cold War armageddon.
Upper Heyford was one of the largest US Air Force bases in Europe, housing bombers that carried NATO's intermediate-range nuclear weapons.
Today, parts of the site are protected as scheduled monuments of national importance, as this is one of the oldest bases in the world with more than 100 years of history.
First used by the Royal Flying Corps in 1916 the airbase was later and more significantly used by United States Airforce as a UK base for strategic bombers, tactical reconnaissance, fighter and fighter-bomber aircraft. The airbase’s flight line was officially closed on 15th December 1993 and in January 1994 the final aircraft was transferred without personnel or equipment, to Carolina, USA. These days the airbase is occupied by rare bird species such as the Peregrine Falcon and Skylark, and houses various business Many of the shops have returned and service the local community, the hospital has been demolished along with other abandoned buildings to make way for new houses
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2020 January 18 An Almost Eclipse of the Moon Image Credit...

2020 January 18

An Almost Eclipse of the Moon
Image Credit & Copyright: Gyorgy Soponyai

Explanation: This composited series of images follows the Moon on January 10, the first Full Moon of 2020, in Hungarian skies. The lunar disk is in mid-eclipse at the center of the sequence though. It looks only slightly darker there as it passes through the light outer shadow or penumbra of planet Earth. In fact during this penumbral lunar eclipse the Moon almost crossed into the northern edge of Earth’s dark central shadow or umbra. Subtle and hard to see, this penumbral lunar eclipse was the first of four lunar eclipses in 2020, all of which will be penumbral lunar eclipses.

∞ Source: apod.nasa.gov/apod/ap200118.html

* This article was originally published here

6th Century Brooch and Multiple Item Mould at Brough of Birsay, National Museum of Scotland,...

6th Century Brooch and Multiple Item Mould at Brough of Birsay, National Museum of Scotland, Edinburgh, December 2019.

* This article was originally published here

Glimpse into ancient hunting strategies of dragonflies and damselflies

Dragonflies and damselflies are animals that may appear gentle but are, in fact, ancient hunters. The closely related insects shared an ancestor over 250 million years ago -- long before dinosaurs -- and provide a glimpse into how an ancient neural system controlled precise and swift aerial assaults.

Glimpse into ancient hunting strategies of dragonflies and damselflies
Damselfly [Credit: M. Hutchinson]
A paper recently published in Current Biology, led by University of Minnesota researchers, shows that despite the distinct hunting strategies of dragonflies and damselflies, the two groups share key neurons in the circuit that drives the hunting flight. These neurons are so similar, researchers believe the insects inherited them from their shared ancestor and that the neurons haven't changed much.

Gaining insight into their ability to quickly process images could inform technological advancements. These findings could inform where to mount cameras on drones and autonomous vehicles, and how to process the incoming information quickly and efficiently.

"Dragonflies and damselflies are interesting from an evolutionary point of view because they give us a window into ancient neural systems," said Paloma Gonzalez-Bellido, assistant professor in the Department of Ecology, Evolution and Behavior in the College of Biological Sciences and senior author on the paper. "And because there are so many species, we can study their behavior and compare their neural performance. You can't get that from fossils."

A noticeable difference between dragonflies and damselflies is the shape and position of their eyes. Most dragonflies today have eyes that are close together, often touching along the top of their head. Whereas damselflies sport eyes that are far apart. The researchers wanted to know whether this made a difference in their hunting habits, and if it affected how their neural system detects moving prey.

Researchers found:

- dragonflies and damselflies hunt prey differently, with dragonflies using a higher resolution area near the top of their eyes to hunt prey from below and damselflies leveraging increased resolution in the front of their eyes to hunt prey in front of them;

- in dragonflies with eyes that merge at the top, the eyes work as if they were two screens of an extended display (i.e. the image of the prey, which would be equivalent to the mouse pointer, can fall on either the left or the right, but never in both screens at the same time);

- damselflies eyes work as duplicated screens, where the prey image is seen by both eyes at once (i.e. they have binocular vision);

- both designs have pros and cons, and their presence correlates with the type of prey and the environment;

- despite different strategies, the neurons that transfer information about a moving target from the brain to the wing motor centers are nearly identical in the two groups -- indicating they were inherited from the common ancestor.

The different hunting strategies pay off in different environments. Dragonflies tend to hunt in an open area, leveraging the contrast of the sky to help them spot their target. Although they can't calculate depth using two images, they rely on other cues. Damselflies tend to hunt among vegetation, where the selective pressure for fast reaction may be absent, or the need for depth perception stronger.

Researchers are now looking to understand how the extended versus duplicated images are calculated in the brain, and how the information is implemented into muscle movements.

"There is still a lot we do not understand," said Jack Supple, first author and a recent PhD graduate from Gonzalez-Bellidos laboratory. "We do not know how these neurons coordinate all the different muscles in the body during flight. If we tried to build a realistic robotic damselfly or dragonfly tomorrow we would have a difficult time."

In addition to examining the differences amongst the two insect families, researchers continue to explore differences in species within each family. "While most dragonflies have eyes close together, there are a handful of species with eyes far apart," said Gonzalez-Bellido. "Some of them are abundant in Minnesota and we are eager to leverage the new flight arena to study their behavior in a controlled setting."

Researchers aim to collect at Cedar Creek Ecosystem Science Reserve and Itasca Biological Station and Laboratories this summer, both areas with diverse populations of dragonflies and damselflies.

Source: University of Minnesota [January 16, 2020]

* This article was originally published here

Fossil is the oldest-known scorpion

Scientists studying fossils collected 35 years ago have identified them as the oldest-known scorpion species, a prehistoric animal from about 437 million years ago. The researchers found that the animal likely had the capacity to breathe in both ancient oceans and on land.

Fossil is the oldest-known scorpion
The fossil (left) was unearthed in Wisconsin in 1985. Scientists analyzed it and discovered the ancient animal's
respiratory and circulatory organs (centre) were near-identical to those of a modern-day scorpion (right)
[Credit: Andrew Wendruff]
The discovery provides new information about how animals transitioned from living in the sea to living entirely on land: The scorpion's respiratory and circulatory systems are almost identical to those of our modern-day scorpions -- which spend their lives exclusively on land -- and operate similarly to those of a horseshoe crab, which lives mostly in the water, but which is capable of forays onto land for short periods of time.

The researchers named the new scorpion Parioscorpio venator. The genus name means "progenitor scorpion," and the species name means "hunter." They outlined their findings in a study published in the journal Scientific Reports.

"We're looking at the oldest known scorpion -- the oldest known member of the arachnid lineage, which has been one of the most successful land-going creatures in all of Earth history," said Loren Babcock, an author of the study and a professor of earth sciences at The Ohio State University.

"And beyond that, what is of even greater significance is that we've identified a mechanism by which animals made that critical transition from a marine habitat to a terrestrial habitat. It provides a model for other kinds of animals that have made that transition including, potentially, vertebrate animals. It's a groundbreaking discovery."

The "hunter scorpion" fossils were unearthed in 1985 from a site in Wisconsin that was once a small pool at the base of an island cliff face. They had remained unstudied in a museum at the University of Wisconsin for more than 30 years when one of Babcock's doctoral students, Andrew Wendruff -- now an adjunct professor at Otterbein University in Westerville -- decided to examine the fossils in detail.

Wendruff and Babcock knew almost immediately that the fossils were scorpions. But, initially, they were not sure how close these fossils were to the roots of arachnid evolutionary history. The earliest known scorpion to that point had been found in Scotland and dated to about 434 million years ago. Scorpions, paleontologists knew, were one of the first animals to live on land full-time.

The Wisconsin fossils, the researchers ultimately determined, are between 1 million and 3 million years older than the fossil from Scotland. They figured out how old this scorpion was from other fossils in the same formation. Those fossils came from creatures that scientists think lived between 436.5 and 437.5 million years ago, during the early part of the Silurian period, the third period in the Paleozoic era.

"People often think we use carbon dating to determine the age of fossils, but that doesn't work for something this old," Wendruff said. "But we date things with ash beds -- and when we don't have volcanic ash beds, we use these microfossils and correlate the years when those creatures were on Earth. It's a little bit of comparative dating."

The Wisconsin fossils -- from a formation that contains fossils known as the Waukesha Biota¬ -- show features typical of a scorpion, but detailed analysis showed some characteristics that were not previously known in any scorpion, such as additional body segments and a short "tail" region, all of which shed light on the ancestry of this group.

Wendruff examined the fossils under a microscope, and took detailed, high-resolution photographs of the fossils from different angles. Bits of the animal's internal organs, preserved in the rock, began to emerge. He identified the appendages, a chamber where the animal would have stored its venom, and -- most importantly -- the remains of its respiratory and circulatory systems.

This scorpion is about 2.5 centimeters long -- about the same size as many scorpions in the world today. And, Babcock said, it shows a crucial evolutionary link between the way ancient ancestors of scorpions respired under water, and the way modern-day scorpions breathe on land. Internally, the respiratory-circulatory system has a structure just like that found in today's scorpions.

"The inner workings of the respiratory-circulatory system in this animal are, shape-wise, identical to those of the arachnids and scorpions that breathe air exclusively," Babcock said. "But it also is incredibly similar to what we recognize in marine arthropods like horseshoe crabs. So, it looks like this scorpion, this lineage, must have been pre-adapted to life on land, meaning they had the morphologic capability to make that transition, even before they first stepped onto land."

Paleontologists have for years debated how animals moved from sea to land. Some fossils show walking traces in the sand that may be as old as 560 million years, but these traces may have been made in prehistoric surf -- meaning it is difficult to know whether animals were living on land or darting out from their homes in the ancient ocean.

But with these prehistoric scorpions, Wendruff said, there was little doubt that they could survive on land because of the similarities to modern-day scorpions in the respiratory and circulatory systems.

Author: Laura Arenschield | Source: Ohio State University [January 16, 2020]

* This article was originally published here

UFOs among us!

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Channel: Terry's Theories  

Here are some good examples of UFOs.
Source video: https://www.youtube.com/watch?v=ogHbA-8xmy0
Source video: Linda Miller https://www.youtube.com/watch?v=xpiIjACtuQM&t=132s

Video length: 6:36
Category: Science & Technology

2nd Century CE Water Bottle, Newstead, National Museum of Scotland, Edinburgh, Scotland, December...

2nd Century CE Water Bottle, Newstead, National Museum of Scotland, Edinburgh, Scotland, December 2019.

* This article was originally published here

In death of dinosaurs, it was all about the asteroid - not volcanoes

Volcanic activity did not play a direct role in the mass extinction event that killed the dinosaurs, according to an international, Yale-led team of researchers. It was all about the asteroid.

In death of dinosaurs, it was all about the asteroid - not volcanoes
Credit: stock.adobe.com
In a break from a number of other recent studies, Yale assistant professor of geology & geophysics Pincelli Hull and her colleagues argue in a new research paper in the journal Science that environmental impacts from massive volcanic eruptions in India in the region known as the Deccan Traps happened well before the Cretaceous-Paleogene extinction event 66 million years ago and therefore did not contribute to the mass extinction.

Most scientists acknowledge that the mass extinction event, also known as K-Pg, occurred after an asteroid slammed into Earth. Some researchers also have focused on the role of volcanoes in K-Pg due to indications that volcanic activity happened around the same time.

"Volcanoes can drive mass extinctions because they release lots of gases, like SO2 and CO2, that can alter the climate and acidify the world," said Hull, lead author of the new study. "But recent work has focused on the timing of lava eruption rather than gas release."

To pinpoint the timing of volcanic gas emission, Hull and her colleagues compared global temperature change and the carbon isotopes (an isotope is an atom with a higher or lower number of neutrons than normal) from marine fossils with models of the climatic effect of CO2 release. They concluded that most of the gas release happened well before the asteroid impact -- and that the asteroid was the sole driver of extinction.

"Volcanic activity in the late Cretaceous caused a gradual global warming event of about two degrees, but not mass extinction," said former Yale researcher Michael Henehan, who compiled the temperature records for the study. "A number of species moved toward the North and South poles but moved back well before the asteroid impact."

Added Hull, "A lot of people have speculated that volcanoes mattered to K-Pg, and we're saying, 'No, they didn't.'"

Recent work on the Deccan Traps, in India, has also pointed to massive eruptions in the immediate aftermath of the K-Pg mass extinction. These results have puzzled scientists because there is no warming event to match. The new study suggests an answer to this puzzle, as well.

"The K-Pg extinction was a mass extinction and this profoundly altered the global carbon cycle," said Yale postdoctoral associate Donald Penman, the study's modeler. "Our results show that these changes would allow the ocean to absorb an enormous amount of CO2 on long time scales -- perhaps hiding the warming effects of volcanism in the aftermath of the event."

Author: Jim Shelton | Source: Yale University [January 16, 2020]

* This article was originally published here

Seagulls grab bread on the fly

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Channel: UFO Odessa  

I decided to feed the seagulls and fed them a loaf of bread, they pretty quickly catch it on the fly.

Video length: 6:35
Category: Entertainment

Roman Glass Jug, Turriff, National Museum of Scotland, Edinburgh, Scotland, December 2019.

Roman Glass Jug, Turriff, National Museum of Scotland, Edinburgh, Scotland, December 2019.

* This article was originally published here

Study traces evolution of acoustic communication

Imagine taking a hike through a forest or a stroll through a zoo and not a sound fills the air, other than the occasional chirp from a cricket. No birds singing, no tigers roaring, no monkeys chattering, and no human voices, either. Acoustic communication among vertebrate animals is such a familiar experience that it seems impossible to imagine a world shrouded in silence.

Study traces evolution of acoustic communication
Frogs, like mammals, originated as predominantly nocturnal animals, but maintained the ability to communicate
acoustically after switching to being active during the day [Credit: Peter Trimming/Creative Commons]
But why did the ability to shout, bark, bellow or moo evolve in the first place? In what is likely the first study to trace the evolution of acoustic communication across terrestrial vertebrates, John J. Wiens of the University of Arizona and Zhuo Chen, a visiting scientist from Henan Normal University in Xinxiang, China, traced the evolution of acoustic communication in terrestrial vertebrates back to 350 million years ago.

The authors assembled an evolutionary tree for 1,800 species showing the evolutionary relationships of mammals, birds, lizards and snakes, turtles, crocodilians, and amphibians going back 350 million years. They obtained data from the scientific literature on the absence and presence of acoustic communication within each sampled species and mapped it onto the tree. Applying statistical analytical tools, they tested whether acoustic communication arose independently in different groups and when; whether it is associated with nocturnal activity; and whether it tends to be preserved in a lineage.

The study, published in the open-access journal Nature Communications, revealed that the common ancestor of land-living vertebrates, or tetrapods, did not have the ability to communicate through vocalization - in other words, using their respiratory system to generate sound as opposed to making noise in other ways, such as clapping hands or banging objects together. Instead, acoustic communication evolved separately in mammals, birds, frogs and crocodilians in the last 100-200 million years, depending on the group. The study also found that the origins of communication by sound are strongly associated with a nocturnal lifestyle.

This makes intuitive sense because once light is no longer available to show off visual cues such as color patterns to intimidate a competitor or attract a mate, transmitting signals by sound becomes an advantage.

Extrapolating from the species in the sample, the authors estimate that acoustic communication is present in more than two-thirds of terrestrial vertebrates. While some of the animal groups readily come to mind for their vocal talents - think birds, frogs and mammals - crocodilians as well as a few turtles and tortoises have the ability to vocalize.

Interestingly, the researchers found that even in lineages that switched over to a diurnal (active by day) lifestyle, the ability to communicate via sound tends to be retained.

Study traces evolution of acoustic communication
Birds, like this marsh wren, rely heavily on acoustic communication to stake out territories
and attract mates [Credit: Alex Badyaev/University of Arizona]
"There appears to be an advantage to evolving acoustic communication when you're active at night, but no disadvantage when you switch to being active during the day," Wiens said. "We have examples of acoustic communication being retained in groups of frogs and mammals that have become diurnal, even though both frogs and mammals started out being active by night hundreds of millions of years ago."

According to Wiens, birds kept on using acoustic communication even after becoming diurnal for the most part. Interestingly, many birds sing at dawn, as every birdwatcher can attest. Although speculative, it is possible that this "dawn chorus" behavior might be a remnant of the nocturnal ancestry of birds.

In addition, the research showed that acoustic communication appears to be a remarkably stable evolutionary trait. In fact, the authors raise the possibility that once a lineage has acquired the ability to communicate by sound, the tendency to retain that ability might be more stable than other types of signaling, such as conspicuous coloration or enlarged, showy structures.

In another unexpected result, the study revealed that the ability to vocalize does not appear to be the driver of diversification - the rate at which a lineage evolves into new species - it has been believed to be.

To illustrate this finding, Wiens pointed to birds and crocodilians: Both lineages have acoustic communication and go back roughly 100 million years, but while there are close to 10,000 bird species known, the list of crocodilians doesn't go past 25. And while there are about 10,000 known species of lizards and snakes, most go about their lives without uttering a sound, as opposed to about 6,000 mammalian species, 95% of which vocalize.

"If you look at a smaller scale, such as a few million years, and within certain groups like frogs and birds, the idea that acoustic communication drives speciation works out," Wiens said, "but here we look at 350 million years of evolution, and acoustic communication doesn't appear to explain the patterns of species diversity that we see."

The authors point out that their findings likely apply not only to acoustic communication, but also to other evolutionary traits driven by the ecological conditions known to shape the evolution of species. While it had been previously suggested that ecology was important for signal evolution, it was thought to apply mostly to subtle differences among closely related species.

"Here, we show that this idea of ecology shaping signal evolution applies over hundreds of millions of years and to fundamental types of signals, such as being able to communicate acoustically or not," Wiens said.

Source: University of Arizona [January 17, 2020]

* This article was originally published here

‘Twelve Apostles’ Prehistoric Stone Circle, Dumfries, Scotland, 12.1.20.

‘Twelve Apostles’ Prehistoric Stone Circle, Dumfries, Scotland, 12.1.20.

* This article was originally published here

Green in tooth and claw

Hard plant foods may have made up a larger part of early human ancestors' diet than currently presumed, according to a new experimental study of modern tooth enamel from Washington University in St. Louis.

Green in tooth and claw
Five skull replicas of human ancestors from left to right: A. africanus, A. afarensis, H. erectus,
H. neanderthalensis and H. sapiens sapiens [Credit: Shutterstock]
Scientists often look at microscopic damage to teeth to infer what an animal was eating. This new research -- using experiments looking at microscopic interactions between food particles and enamel -- demonstrates that even the hardest plant tissues scarcely wear down primate teeth. The results have implications for reconstructing diet, and potentially for our interpretation of the fossil record of human evolution, researchers said.

"We found that hard plant tissues such as the shells of nuts and seeds barely influence microwear textures on teeth," said Adam van Casteren, lecturer in biological anthropology in Arts & Sciences, the first author of the new study in Scientific Reports. David S. Strait, professor of physical anthropology, is a co-author.

Traditionally, eating hard foods is thought to damage teeth by producing microscopic pits. "But if teeth don't demonstrate elaborate pits and scars, this doesn't necessarily rule out the consumption of hard food items," van Casteren said.

Humans diverged from non-human apes about seven million years ago in Africa. The new study addresses an ongoing debate surrounding what some early human ancestors, the australopiths, were eating. These hominin species had very large teeth and jaws, and likely huge chewing muscles.

"All these morphological attributes seem to indicate they had the ability to produce large bite forces, and therefore likely chomped down on a diet of hard or bulky food items such as nuts, seeds or underground resources like tubers," van Casteren said.

But most fossil australopith teeth don't show the kind of microscopic wear that would be expected in this scenario.

The researchers decided to test it out.

Previous mechanical experiments had shown how grit -- literally, pieces of quartz rock -- produces deep scratches on flat tooth surfaces, using a device that mimicked the microscopic interactions of particles on teeth. But there was little to no experimental data on what happens to tooth enamel when it comes in contact with actual woody plant material.

For this study, the researchers attached tiny pieces of seed shells to a probe that they dragged across enamel from a Bornean orangutan molar tooth.

They made 16 "slides" representing contacts between the enamel and three different seed shells from woody plants that are part of modern primate diets. The researchers dragged the seeds against enamel at forces comparable to any chewing action.

The seed fragments made no large pits, scratches or fractures in the enamel, the researchers found. There were a few shallow grooves, but the scientists saw nothing that indicated that hard plant tissues could contribute meaningfully to dental microwear. The seed fragments themselves, however, showed signs of degradation from being rubbed against the enamel.

This information is useful for anthropologists who are left with only fossils to try to reconstruct ancient diets.

"Our approach is not to look for correlations between the types of microscopic marks on teeth and foods being eaten -- but instead to understand the underlying mechanics of how these scars on tooth surface are formed," van Casteren said. "If we can fathom these fundamental concepts, we can generate more accurate pictures of what fossil hominins were eating."

So those big australopith jaws could have been put to use chewing on large amounts of seeds -- without scarring teeth.

"And that makes perfect sense in terms of the shape of their teeth" said Peter Lucas, a co-author at the Smithsonian Tropical Research Institute, "because the blunt low-cusped form of their molars are ideal for that purpose."

"When consuming many very small hard seeds, large bite forces are likely to be required to mill all the grains," van Casteren said. "In the light of our new findings, it is plausible that small, hard objects like grass seeds or sedge nutlets were a dietary resource for early hominins."

Source: Washington University in St. Louis [January 17, 2020]

* This article was originally published here


https://t.co/hvL60wwELQ — XissUFOtoday Space (@xufospace) August 3, 2021 Жаждущий ежик наслаждается пресной водой после нескольких дней в о...