Stories tagged Biological Populations Change Over Time
Does this make my feet look baboonish?: Some folks among us have more ape-like feet than others.Courtesy Mark RyanA recent study of visitors to the Boston Museum of Science has revealed that some humans - about 1 in 13 - have feet that are ape-like in their structure.
Our great-ape cousins such as chimpanzees have feet that are very flexible in their middle region due to something called the midtarsal break that allows their feet to bend in the middle, enabling them to grasp at branches for easier climbing through trees. So when a chimp lifts his foot off the ground, it just flops about - there's nothing to hold the bones together. Most humans, on the other hand (or should I say foot?), have the same joint but have ligaments that stretch across it making the foot more rigid and stable for upright walking. Australopithecus sediba, a human ancestor that lived 2 million years ago, has a foot structure that is more ape-like than human, so somewhere along the line our feet evolved probably to accommodate our bipedalism.
The study was done by Jeremy DeSilva, a functional morphologist from Boston University, whose main interest is the evolution of the human foot and ankle. In this recent study, museum visitors were requested to walk barefoot across a mechanized carpet while DeSilva's team observed their gaits and the structure of their feet as they walked.
The surprising results showed that 8 percent of the nearly 400 participants possessed a flexible midtarsal break in their foot, and displayed a pressure signature in their footprint that looked like that found in the footprints of non-human primates. Perhaps more surprising is the fact that those subjects who had the unusual foot-joint structure weren't even aware of it until DeSilva revealed it to them.
The study was published in the American Journal of Physical Anthropology.
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Coelacanth: model in the SMM paleo lab. Photo by Mark Ryan.Courtesy Fancy Horse (underwater background)The genome of the coelacanth, the world's best known living fossil, has been sequenced by an international team of researchers and is revealing something scientists already suspected: that the primitive-looking fish has evolved more slowly than most other organisms. The coelacanth is related to the lungfish and several extinct Devonian fish species that are considered precursors to land dwelling tetrapods. Kerstin Lindblad-Toh is senior author of the study which appeared recently in the science journal Nature.
"We often talk about how species have changed over time, but there are still a few places on Earth where organisms don't have to change, and this is one of them," Lindblad-Toh said. "Coelacanths are likely very specialized to such a specific, non-changing, extreme environment -- it is ideally suited to the deep sea just the way it is."
Lindblad-Toh is scientific director of the Broad Institute's vertebrate genome biology group in Cambridge, Massachusetts, which did the genome research. The institute is linked to both MIT and Harvard.
The genetic map, which involved sequencing some 3 billion letters of DNA, also showed (via RNA content) that tetrapods - four-legged land dwelling animals - though related to both coelacanths and lungfish, are more closely related to lungfish and followed that line rather than that of the coelacanth. We humans also branched off that same line. The genome of a lungfish is composed of over 100 billion DNA letters, making it a much more difficult task to sequence, so for the time being, the coelacanth's DNA makes for a reasonable alternative for study.
"This is just the beginning of many analyses on what the coelacanth can teach us about the emergence of land vertebrates, including humans, and, combined with modern empirical approaches, can lend insights into the mechanisms that have contributed to major evolutionary innovations," said professor Chris Amemiya at the University of Washington, and the paper's co-author.
Fossil coelacanth: not much has changed in 350 million years.Courtesy photo by Haplochromis via Wikipedia Creative CommonsWhen Louis Agassiz named the first fossil coelacanth back in 1836, the Swiss paleontologist probably never imagined that a nearly identical descendent of the primitively constructed Devonian-aged fish would one day be found still inhabiting the world's oceans. The coelacanth was thought to have gone extinct along with the non-avian dinosaurs at the end of the Cretaceous period. None have been found in the fossil record after that time, but two extant species are known today. The first specimen Latimeria chalumnae was netted off the coast of South Africa in 1938, near the Chalumnae river and retrieved by East London Museum curator Marjorie Courtenay-Latimer who discovered what she called "the most beautiful fish I'd ever seen" in the catch of local fisherman, Henrik Goosen. Since then several more coelacanths have been caught, including the Indonesian species, Latimeria menadoensis, from the Indian Ocean.
The remarkable prehistoric throw-back, sometimes referred to as "old four legs" because of its leg-like fins, hasn't changed much in its 350 million year history. A member of the clade of lobe-finned fishes called Sarcopterygii, coelacanths retain primitive characteristics such a notochord, a hollow fluid-filled tube made of cartilage that underlies the spine over the length of its body. In all other vertebrates, the notochord is an anatomical structure that appears briefly only during the embryonic stage but not in adults. Not so with the coelacanth. It also possesses, primitive shark-like intestines, a linear heart, and tightly-woven armor-like scales (known as cosmoid) that are only found on extinct species of fish. The coelacanth's brain case contains only 1.5 percent gray matter - the other 98.5 percent of space is filled with fat. The other end of the coelacanth body begins to taper before expanding into a strange, three-lobed tail. Its most notable features are its lobed pectoral and pelvic fins that are structured with bones that look like toes, and move in an alternating tetrapod manner. An electroreceptive rostal organ located in its snout is used to detect prey, and the coelacanth is the only living animal that can unhinge a section of the its cranium to increase the gape of its mouth, enabling it to consume larger prey.
The blue or brown, white-speckled coelacanths prefer deep-water environments, and can reach six and a half feet in length and weigh upwards to 175 pounds. For some reason no living coelacanth has managed to survive more than a single day in captivity. With a dwindling population estimated at only 500-1000 individuals, the coelacanth was declared an endangered species in 1989.
SOURCE and LINKS
Broad Institute news
Coelacanth info at dinofish.com
More coelacanth info
NatGeo article
Take Nova's Coelacanth Quiz
OMG! Can nothing stop them?: According to a new study, mosquitoes, those buzzing, biting, itch-producing flying pests that make life miserable for many of Earth's inhabitants (mainly we humans), can easily adapt to Deet, one of the commonly used ingredients in insect repellents.Courtesy Mark Ryan (with photo help from NASA)
We've all seen them, those great B-films where a giant, vicious monster from under the sea, or invaders from outer space arrive to cause mayhem across our cities and generally mess up our way of life. In the end, it seems no matter who or what it was that was attacking us, be it Mothra, Godzilla, or some race of belligerent extra-terrestrials, we could always count on the military to save our collective behind.
Unfortunately, with mosquitoes, that might now be the case anymore.
Scientists are reporting that Deet, one of the most widely used active ingredients in insect repellents, loses its effectiveness against mosquitoes shortly after those ubiquitous, blood-seeking winged vermin are first exposed to it.
Deet - the common name for N,N-diethyl-meta-toluamide - was developed by the US Army after the Second World War to help combat insects during jungle warfare. It was used extensively in the Korean and Vietnam wars, but mosquitoes seem to be able to adapt quickly to it.
"Mosquitoes are very good at evolving very very quickly", said Dr. James Logan of the London School of Hygiene and Tropical Medicine and co-author of the study. "There is something about being exposed to the chemical that first time that changes their olfactory system - changes their sense of smell - and their ability to smell Deet, which makes it less effective."
So what I want to know is where does that leave us here in Minnesota where the mosquito constantly competes with the Common Loon for the title of State Bird? Maybe it's time to start digging the bunker in the backyard.
SOURCE and LINKS
BBC Science news
Original study at Plos One
The Life Cycle of the Mosquito
All about mosquitoes on NatGeo
![Dead zombie bee: Up to 80 percent of bee hives along the West Coast may be impacted by the "zombie bee" phenomenon. Parasite flies plants inside the bees, like this one, that ultimately kill them.](/sites/default/files/images/zombiebee-small.jpg "Dead zombie bee: Up to 80 percent of bee hives along the West Coast may be impacted by the "zombie bee" phenomenon. Parasite flies plants inside the bees, like this one, that ultimately kill them.")
Dead zombie bee: Up to 80 percent of bee hives along the West Coast may be impacted by the "zombie bee" phenomenon. Parasite flies plants inside the bees, like this one, that ultimately kill them.Courtesy wintersixfourZombies are all the rage these days, and not just on cable TV shows or at pub crawls.
The impacted bees get their name for their changing behaviors once they host the parasitic flies that cause the trouble. While most bees spend their nights nestled snuggling in a comb, these "zombie bees" actually go out flying in very erratic patterns. Like many other night bugs, the zombie bees fly to light and usually die quite soon.
What's really at play is that the tiny parasitic flies plant eggs into the host bee. Those eggs grow into maggots that eat the inside of the host bee that ultimately cause its demise.
Evidence of zombie bees was first found in 2008 near Sacramento, Calif., and beekeepers around the west coast have seeing the spread of the problem in the years since.
Researchers are trying to figure out if this parasite problem is a factor in the bee population declines that have been going on nationwide. One researcher has set up a website – ZombeeWatch.org – to allow amateur beekeepers to share information about zombie bees they are finding around their hives. It is also looking for people who want to step forward to be "zombee hunters."
There has been one isolated report of zombie bees in South Dakota. So far, two investigations in Minnesota have turned up no evidence of zombie bees.
Prehistoric Antarctica shoreline: artist's conception of flora living during the Middle Miocene epoch.Courtesy NASA / JPL-Caltech / Dr. Philip Bart, LSURecent investigations into microfossils show that Antarctica hasn’t been quite the icebox scientists have imagined it to be over the past 34 million years. Pollen and leaf wax samples from Miocene-aged sediments indicate the continent has experienced some periods of warming since the beginning of the most recent glacial period. The core samples studied came from ocean sediments collected near Antarctica, and particulates found in the samples indicate more rain fell on the ice-covered continent during the Middle Miocene epoch (15.5 – 20 million years ago) than previously thought, enough rain to spur the growth of forests of small, stunted trees.
Paleoclimatologist and organic geochemist Sarah Feakins of the University of Southern California and her colleagues analyzed core samples taken from between 144 and 1,100 meters beneath the ocean floor – levels dating back to the Middle Miocene. Spikes of concentrated amounts of pollens and leaf wax appeared in two periods – one about 16.4 million years ago, and another about 15.7 million years ago. The warm periods were relatively short, each lasting less than 30,000 years.
In a previous study, palynologist Sophie Warny of Louisiana State University had first described the pollen and leaf wax spikes found in the core samples, and she and Feakins eventually teamed up for the recent study. The team determined the particle spikes didn’t arise from the leaf wax and pollen blowing in from elsewhere but rather came from two species of trees that once lined the shores of Antarctica. The two species, podocarp conifer and southern beech wouldn’t have grown very tall – maybe knee-high – and neither spreads their pollen over wide areas. Had the pollens blown in from elsewhere - say South America or New Zealand - there were would have been more species in the mix.
Using a mass spectrometer, Feakins and NASA researchers analyzed the ratio of hydrogen to deuterium atoms in the wax molecules which indicated the temperature at the Antarctica location during the two warm periods was about 7 degrees Celsius during the summer. Today, summer temperatures in the same region are about –4 °C. The average global temperature at the time was about 3 °C higher than it is today. As the overall global temperature changes a relatively greater change in polar temperature isn't unexpected due to a process called polar amplification.
The data from Feakins and Warny’s study, which appeared in Nature Geoscience, adds to growing concerns over the sensitivity of Earth’s climatic and hydrological systems. At the moment, no trees line the shores of Antarctica, but current levels of carbon dioxide (393 parts per million) are not far off those thought to have existed during the Middle Miocene’s warm periods (400-600 parts per million) when forests did exist on the margins of the icy continent. This could indicate that even small changes in carbon dioxide levels can are capable of creating big changes in climate.
SOURCES
Earth magazine
Science on NBCnews.com
Evolution timeline from 1882: This caricature of Darwin's theory appeared in the 1882 Punch Almanac. The recent evolution timeline created by Kyrk and Sezen is a bit of an improvement.Courtesy Public domain via Wikipedia This cool evolution timeline is really fascinating and fun to mess around with. I'm guessing Charles Darwin would agree it's a vast improvement over the one that appeared in Punch Almanac in1882 when he was still alive (see image at right). This new one was created by John Kyrk, a biology-trained artist in San Francisco in collaboration with Dr. Uzay Sezen, a plant biologist from the University of Georgia. The timeline is available in several languages and would be very useful in a classroom setting when studying evolution and paleontology.
The site is interactive and follows the evolution of our universe from the Big Bang to the present. You start it by clicking and sliding the red pyramid on the right. As you scroll across the timeline, various events in the history of the Universe, Solar System and ultimately, the Earth show up on the screen. All along, links also appear that either explain concepts or show examples of them. In the upper left hand corner is a menu linking you to several corollary Flash animations by Kyrk explaining cell biology and how RNA, DNA, cells, water, and other basic elements of life (including viruses) operate. Kyrk thinks animated illustrations are very useful in teaching and remembering ideas and concepts.
All the phases of Earth’s formation and development are covered in the evolution timeline, including the Late Heavy Bombardment, Snowball Earth, Cambrian Explosion, stromatolites, photosynthesis and iron formation. Once life begins to rise up, your computer screen will run amok with Earth’s diverse species populations from the one-celled animals, trilobites and fish to amphibians, reptiles, dinosaurs and mammals – the whole shooting match. All the major extinction events are shown, too.
The site also contains a link to this YouTube video version of someone else working the timeline so you can just sit back and watch how it happens, But I recommend working the interactive page yourself. A lot more happens and is available than the video allows you to see. Note that you’ll need Flash for it to run on your computer.
I wonder how Darwin would have reacted if he were able to see his theory illustrated in this way?
SOURCES
Evolution Timeline
Cumulative impact by humans on the oceanCourtesy National Center for Ecological Analysis and SynthesisOne of the great extinctions in Earth history occurred 252 million years ago when about 95 percent of all marine species went extinct. The cause or causes of the Great Dying have long been a subject of much scientific interest.
Now careful analyses of fossils by scientists at Stanford and the University of California, Santa Crux offer evidence that marine animals throughout the ocean died from a combination of factors – a lack of dissolved oxygen, increased ocean acidity and higher water temperatures. What happened to so dramatically stress marine life everywhere?
Geochemical and fossil evidence points to a dramatic rise in the concentration of carbon dioxide in the atmosphere, which in caused a rapid warming of the planet and resulted in large amounts of carbon dioxide dissolving into the ocean and reacting with water to produce carbonic acid, increasing ocean acidity. The top candidate for all this carbon dioxide? – huge volcanic eruptions over thousands of years in what is now northern Russia.
Why should the Great Dying be of more than just academic interest? Humans currently release far more carbon dioxide into the atmosphere than volcanoes and we are releasing carbon dioxide into the atmosphere at a rate that greatly exceeds that believed to have occurred 252 million years ago. The future of Earth’s oceans will be determined by human decision making, either by default or by design. What do we want our future ocean to be?
Skull of Yutyrannus hualiCourtesy Photo by Zang Hailong (via Nature)A huge one-and-a-half ton theropod discovered recently in China is further shaking up our old ideas of dinosaurs being oversized scaly lizards. The fossilized remains of Yutyrannus huali, a 130 million year-old tyrannosaur uncovered in the Liaoning fossil beds show evidence of a fuzzy coating of feathers on several areas, e.g. the tail, hip, foot, neck and arm. Yutyrannus huali is a distant relative of Tyrannosaurus rex(there is some contention about this) which didn’t evolve until much later in the Cretaceous period. Evidence of feathers has been found on smaller dinosaurs including the basal tyrannosauroid Dilong but these are the first clues that larger dinosaurs had feathers. Three nearly complete and well-articulated skeletons of Y. huali - an adult and two juveniles were found in the Lower Cretaceous Yixian Formation of Liaoning Province in northeast China. The adult is quite large, being nearly 30 feet in length and estimated to have weighed in life around 3000 pounds! The two juveniles weighed around 1200 pounds. All show evidence of having filamentous feather. Large animals today, such as elephants, rhinos, and hippos are somewhat hairless and tend not to need insulation for retaining heat because of their size and the ratio of surface area of skin to their masses. Whether Yutyrannus huali’s well-known descendent Tyrannosaurus rex had any plumage remains a mystery. T. rex was six times as massive as its ancestor, and arrived on the scene 60 million years later in the Late Cretaceous when the climate was warmer. But all it takes to change that is some new fossil to come to light. Generally, it’s thought that feathers first appeared as a means of insulation, species identification, or for attracting mates long before they evolved for use in flight. Today, birds are considered the descendents of small theropods dinosaurs called dromeosaurids. The discovery of Yutyrannus huali adds new clues and additional mystery to our conception of how dinosaurs appeared in life. The new study by Chinese vertebrate paleontologist Xu Xing and his co-researchers appears in the science journal Nature.
SOURCES
National Geographic story
Nature article
NY Times story
Smithsonian's Tracking Dinosaurs
Iridescence is usually a vanity thing in nature; birds and butterflies, for instance, use it to attract mates. This is 
Golden Mole: The tiny structures that help streamline the mole and make it water-repellant also give it its iridescence.Courtesy Killer18the type of thing that would be completely lost on a blind mole...or is it? In the case of the golden mole, iridescence is very much a part of its appearance, but according to a new study about the structure of hair, this iridescence takes on a more functional role. The nano-sized structures on the flattened, paddle-shaped hairs not only give the moles a lovely sheen (for animals that can actually see them), but may also help to repel water and streamline the moles as they move through the sand. This is definitely a case of function over form.
Yesterday, I had the pleasure of attending Environmental Initiative's 2012 Legislative Preview, part of their Policy Forum series.
Basically, a bipartisan group of legislators discussed their environmental priorities with a diverse audience of public, private and nonprofit representatives for the purpose of providing
"a valuable first look at the most pressing environmental issues facing the state in anticipation of the upcoming legislative session."
MN Most Wanted: Asian carp, aquatic invasive speciesCourtesy State of Michigan
The biggest surprise to yours truly was the prevalence of carp among the discussion. Asian carp, AIS (aquatic invasive species), etc., etc.. Everyone appeared in agreement regarding the threat posed by carp, so the real question is what do we do about their impending invasion?
One repeated suggestion was to fund more research, specifically at the University of Minnesota. This is probably an important step towards defending our state waterways, and I think this story helps illustrate why:
"As yet, no technology can stop these downstream migrations; neither grates nor dangerous, expensive electrical barriers do the job.
But a wall of cheap, harmless bubbles just might—at least well enough to have a significant benefit."
Researchers at the U of MN have discovered that bubble barriers may deter 70-80% of carp migration. It's not the visual affect of the bubbles that prevents all but the most daring carp from penetrating the barrier, rather the noise -- equivalent to what you or I would experience standing about three feet from a jackhammer.
The bubble barrier has currently only been tested on common carp, but researchers involved in the experiment want to test the technology on Asian carp next.
In addition to the bubble barrier, U of M researchers are investigating whether Asian carp pheromones can be used to lure them into traps.
