Stories tagged Biological Populations Change Over Time

Mar
20
2010

Dino killer
Dino killerCourtesy Donald Davis (for NASA)

How Earth impact kills dinos

As "mdr" explained recently in, astroid found guilty of killing dinosaurs that a panel of scientists, after reviewing all evidence, blame an asteroid impact for the demise of the dinosaurs.

Ozone killed the dinosaurs

A paper has just been published saying that dinosaurs choked on ozone.

A new study in the journal Paleogeography, Paleoclimatology, Paleoecology puts forth the idea that the Chicxulub impact, long blamed for the extinction of the dinosaurs at the end of the Cretaceous era 65 million years ago, could have done them in by flinging huge amounts of ozone precursor chemicals -- nitrogen oxides, methane, and other hydrocarbons -- into the air.

Below the article in Discovery News, this comment by 1sang (Doug) explains why mammals and avians survived.

In order to (survive) all you'd have to do is get on steeper slopes and find enough food to live for a couple of years. Mammals and smaller avian dinosaurs could more easily accomplish this than their massive cousins (in fact, many were probably already in this safety zone away from the many large predators roaming the lowlands).

He also notes that methane release leads to an increase in ozone and that today we have the beginnings of lots of methane being released (I wrote about this here: Methane ice).

Mar
16
2010

Old school way of thinking: This idea of man as the be-all, end-all of evolution- the unchanging, final edit of nature- is exactly what the Smithsonian's new exhibition hall is trying to negate.
Old school way of thinking: This idea of man as the be-all, end-all of evolution- the unchanging, final edit of nature- is exactly what the Smithsonian's new exhibition hall is trying to negate.Courtesy wikimedia
The Smithsonian Institute will open a new exhibition hall tomorrow (March 17, 2010), the David H. Koch Hall of Human Origins (this opening coincides with the institute’s 100-year anniversary). The 15,000-square-foot hall will focus on what it means to be human, examining how our defining characteristics emerged over time. One cool thing about the new exhibition (in addition to…everything) is the highlight (in the form of bronze statues) of a-typical hominid species. There’s a statue of Homo heidelbergensis, Paranthropus boisei, and even Homo floresiensis (the “hobbit” species). Now, I know what you’re thinking, “What?! Where’s the Australopithecus africanus?!!” Well, it’s not in this exhibition (at least not in the form of a shiny effigy). The reason for this is to emphasize that our ancestry is not a straight line (as A. africanus might imply because it is a possible direct ancestor of Homo sapiens). Instead, our lineage is much less tidy; there’s species overlap, some species die off… the diagrams are messy. The David H. Koch Hall of Human Origins is trying to get at the fact that we Homo sapiens are just another iteration in our branch-laden tree, not the pinnacle of evolutionary development. I think that’s a great point to remind people of.

Other features of the exhibition include forensically reconstructed life-sized faces of some of our ancestors, 75 skull reproductions, key events in humanity’s evolution (environmental changes, behavioral innovations, etc.), a human family tree, and virtual tours of important research sites. I haven’t had the chance to visit it yet, but the American Museum of Natural History in New York also has a relatively new human origins exhibition. I think it’s exciting that more and more museums are taking on this topic. In the past museums have shied away from it for fear of stirring up controversy. The Milwaukee Public Museum, for example has an exhibit about evolution- it’s on a tiny wall in a dark corner…but at least they have one. It’s important for museums to present scientific research, and the exciting exploration of human evolution is no exception. So if you’re in the D.C. area, be sure to check out the new Smithsonian Hall of Human Origins.

Mar
06
2010

What sent the dinosaurs packing?: The number one suspect, a gigantic asteroid, has finally been convicted of the crime.
What sent the dinosaurs packing?: The number one suspect, a gigantic asteroid, has finally been convicted of the crime.Courtesy Mark Ryan
After studying all available evidence and listening to alternative theories (and despite no eyewitnesses), a panel of 45 international scientists has decided it was a huge asteroid that killed all the non-avian dinosaurs some 65 million years ago.

The asteroid, described as a 7 mile-in-diameter chunk of space rock, has been the prime suspect in the ruling reptile’s demise ever since scientists Luis Alvarez and his son Walter first identified a one-inch layer of iridium in Late Cretaceous-age rock exposures throughout the world. The layer was located exactly at the point in the rock record where the Cretaceous period ended, and the Tertiary period began (K-T boundary). Smoking gun for dinosaurs' demise: K-T Boundary with 1-inch iridium layer (arrow) exposed 10 miles west of Trinidad, Colorado. The element iridium is very rare on Earth but concentrated in meteors and comets. The same iridium layer is found in several exposures around the world, and corresponds in age with the Chicxulub meteor crater in Mexico's Yucatan Peninsula. The layer marks the end of the Cretaceous era, and no non-avian dinosaur remains have ever been found above the boundary. The coal layers above and below the iridium suggests a swampy environment when the layer was laid down in this area of Colorado.
Smoking gun for dinosaurs' demise: K-T Boundary with 1-inch iridium layer (arrow) exposed 10 miles west of Trinidad, Colorado. The element iridium is very rare on Earth but concentrated in meteors and comets. The same iridium layer is found in several exposures around the world, and corresponds in age with the Chicxulub meteor crater in Mexico's Yucatan Peninsula. The layer marks the end of the Cretaceous era, and no non-avian dinosaur remains have ever been found above the boundary. The coal layers above and below the iridium suggests a swampy environment when the layer was laid down in this area of Colorado.Courtesy Mark Ryan
They predicted a meteor impact crater of the same age would be found as the source of the iridium since the element is rare on Earth but common in outer space. Then in 1990 their predictions were verified when the Chicxulub impact crater was discovered in Mexico.

Although the impact site was mostly submerged off the north coast of the Yucatan Peninsula, samples taken from it dated to the end of the Cretaceous period. This and other corroborating evidence helped bolster the killer asteroid hypothesis as the primary theory for the extinction event that wiped out 70-75 percent of life on Earth including non-avian dinosaurs, and other large reptiles. The asteroid is estimated to have slammed into Earth traveling 10 times faster than a rifle bullet, and released the energy of a billion atomic bombs. The impact instantly vaporized a large area of terrain, and sent an explosion of dust and rocky debris up into space, much of which fell back into the atmosphere in a fiery rain. It left a crater 110 miles across, and a cloud of dust circling the planet for weeks. The diminished sunlight would have disrupted the environment severely, including the food chain. Mammals and other smaller creatures were able to survive across the boundary and flourish in later periods.

But not everyone was convinced by the evidence. Other causes for the mass extinction, such as extreme volcanism in India, falling sea levels, disease epidemics, and even fungal infection were all tossed around as possible culprits.

But in the end it seems the evidence implicating the asteroid in the K-T* extinction event was just too strong, and after much deliberation, the impact has been determined as the official cause of death. The panel published its decision in the latest issue of Science.

*“K-T” stands for Cretaceous-Tertiary, however, use of the term Tertiary is being discouraged now, and the time span it occupied has been replaced with the Paleogene and Neogene periods. So a more proper, up-to-date term would be Cretaceous-Paleogene or K-Pg extinction event.

LINKS AND SOURCES
More about dinosaur extinction
BBC story
Impact theory counterview

Mar
04
2010

Missing Link - Not

Darwinius masillae
Darwinius masillaeCourtesy University of Oslo
Perhaps taking advantage of the Darwin publicity last year (200th birthday), a scientific paper was published revealing Ida, a 47 million year old fossil classified Darwinius masillae.
The study's lead author, Jørn Hurum of the University of Oslo, variously called the fossil the holy grail of paleontology and the lost ark of archeology. A two-hour documentary called "The Link" was on the History Channel and a book with the same title hit bookstores.

One million dollars

How big money became mixed with science is described in the Guardian post titled Deal in Hamburg bar led scientist to Ida fossil, the 'eighth wonder of the world'.
Now that money has been made, it is time for the scientific process (peer review).

John Fleagle, a professor at Stony Brook University, in New York state, who reviewed the paper for the journal, agrees that the fossil is not a lemur. But Ida's full significance would not be known until other scientists had seen the paper. "That will be sorted out, or at least debated extensively, in the coming years."

Confirmed: Fossil Ida is not a human ancestor

In a paper in the Journal of Human Evolution, Chris Kirk strongly argue(d) that Darwinius is not one of our ancestors. Science blogger, Brian Switek, also explains why ... That "Ida" is Not Our Great-Great-Great-Great-Etc. Grandmother. Dissenting scientists are awaiting a response from Jørn Hurum.

How science should be done

I am reminded of another case where the media was used to hype a story before it was properly reviewed by others. I wrote about it here: Jesus and family found in tomb? What moral is to be learned here?

Don't announce discoveries through the media, but through the tried and tested peer-review process.

Feb
25
2010

An Instant Classic: Hey, Aesop, what if I told you Mr. Hare won the race?
An Instant Classic: Hey, Aesop, what if I told you Mr. Hare won the race?Courtesy Milo Winter

You’re probably familiar with Aesop’s classic fable The Tortoise and the Hare: Mr. Hare challenges Mr. Tortoise to a foot race. Mr. Tortoise accepts. Mr. Hare dashes from the start line, but stops just before the finish line to take a nap. In the meantime, Mr. Tortoise plods along to win the race!! The moral of the story? University of Minnesota professor and Institute on the Environment resident fellow, Dr. Peter Reich’s award-winning take on the fable may surprise you.

Dr. Peter Reich: This guy studies leaves for a living.
Dr. Peter Reich: This guy studies leaves for a living.Courtesy Regents of the University of Minnesota

Dr. Reich studies leaves. In particular, Dr. Reich has discovered three characteristics of leaves that allow researchers to identify where and how plants live: longevity, productivity, and nitrogen content. Longevity measures how old a leaf lives. Did you know leaves in the tropics live only 5-6 weeks whereas Canadian spruce leaves can live up to 18 years old? Productivity measures how much sugar the leaf makes (yes, leaves make sugar called “glucose,” which nearly every animal uses to fuel their body – that’s why your momma tells you to eat your vegetables!). Finally, nitrogen is like a vitamin for plants: they need it to grow big and strong. How much nitrogen a leaf has is important because it determines how much energy a plant can make.

Canadian Spruce: If these leaves were human, they could be legal adults!
Canadian Spruce: If these leaves were human, they could be legal adults!Courtesy Steven J. Baskauf

Tropical Leaves: These guys may look BIG, but they are not going to be around for long.
Tropical Leaves: These guys may look BIG, but they are not going to be around for long.Courtesy Flickr

What about the moral of The Tortoise and the Hare? Dr. Reich’s research says there are basically two types of leaves: ones that are like Mr. Tortoise and ones like Mr. Hare. Tortoise-like leaves work slowly, but steadily. They’re the marathon runners of the leaf world. Hare-like leaves work really fast! But they can’t keep it up for long. They’re sprinters. Could you run a marathon at your top sprinting speed? Probably not, and neither can leaves be both ultra-fast and long-lasting at the same time. Instead, leaves “tradeoff” speed for endurance. Like human runners, leaves don’t have to be all fast and short-lived or all slow and long-lived; they can fall somewhere inbetween and be medium speed and medium-lived.

So who cares about marathon and sprinting leaves anyway? Lots of people! Dr. Reich just won the BBVA Frontiers of Knowledge Award in recognition of this important research. Being able to group the thousands of plants out in the world into a handful of groups is allowing scientists to do incredible research that can be used around the world.

For example, Dr. Reich’s newest research is looking at the different responses of tortoise-leaves versus hare-leaves to changing environments, such as higher levels of carbon dioxide in the air caused by climate change. As each generation of leaves reproduces, new genetic combinations are created. New genetic traits that are helpful to the plant’s survival are passed on to the next generation. The more genetic combinations created, the better chance a species has of “finding” the right traits in a changing environment. This is where Dr. Reich’s interpretation of the moral of The Tortoise and the Hare may surprise you: because hare-leaves have fast, short lives, they reproduce more genetic combinations and are better able to deal with change. Tortoise-leaves will struggle more to adapt. That is, for leaves, slow and steady does not always win the race!

Want to know more?? Dr. Reich recently gave a lecture as part of the Institute on the Environment’s Frontiers on the Environment series. You can hear it here.

Feb
19
2010

Rex in the hen house
Rex in the hen houseCourtesy Mark Ryan
A new study came out last week that appeared destined to shake up the current line of thought that birds descended from dinosaurs. Birds share common traits with some dinosaurs, including furculas (wishbones), hollow bones, and other skeletal features, which scientists have interpreted to mean the former descended from the latter. But now a new study by researchers at Oregon State University, it may have happened just the opposite way.

"We think the evidence is finally showing that these animals which are usually considered dinosaurs were actually descended from birds, not the other way around," said John Ruben, a professor of zoology at OSU, and the study’s lead author.

The study involved the fossil of a Microraptor, a dromaeosaurid dinosaur with evidence of feathers on both its arms and legs. Studying the skeletal remains, Ruben and his colleagues constructed 3-dimensional models that they tested for flight capabilities. Their study showed Microraptor’s structure better suited to be glider rather than a flyer. From this Ruben extrapolated that it made more sense that Microraptor descendents came down from the trees and eventually evolved into flightless birds we call dromaeosaurs or raptors.

"Raptors look quite a bit like dinosaurs but they have much more in common with birds than they do with other theropod dinosaurs such as Tyrannosaurus," he said. The study appears in the journal for the Proceedings of the National Academy of Science (PNAS).

Sounds good at first, and I have to admit I was smitten with the idea. But not everyone feels the same way.

Over at the Smithsonian’s Dinosaur Tracking blog, freelance science writer Brian Switek has pointed out that Ruben’s proclamation is “actually only a commentary, or the equivalent of an opinion piece.”

He then goes on to point out some of the flaws in Ruben’s argument, particularly the uncertainty surrounding Microraptor’s place in the evolution of flight, and the lack of reasonable evidence that Velociraptor wasn’t a dinosaur. Switek doesn’t think Ruben’s claim stands up to scrutiny.

But what annoys Switek most is how the media inundates the various outlets with this kind of science news, giving it wide distribution and often, undeserved credibility.

“In this increasingly fragmented media landscape, knowledgeable science writers who recognize a fishy story when they see one are getting outnumbered. More often, websites and newspapers simply reprint press releases issued by universities and museums (science writers call this “churnalism”), and this policy sometimes lets questionable science slip through the cracks.” – Brian Switek

One of the reasons for this is the internet. There's just a huge amount of time and space that requires constant feedings of content now. It does make things difficult to sort through. There have been times I’ve begun researching some new science story to post on Science Buzz only to become frustrated with details that don’t seem to add up, confusing statements, info that counters other info, and outright misinformation. Some of it may be due to the writer(s) not being able to properly articulate or distill a particular idea or hypothesis for the general reader (I know I suffer from this occasionally). Sometimes it’s due to the fact that many science writers lack access to the papers themselves (most science journals require paid subscriptions to access anything beyond an abstract of the story), so writers are left with relying on press releases and abstracts or another writer’s thoughts on the subject (like I’m doing here). But other times it ends up being that there’s no real story at all, just a rehash of something from months or years ago that somebody figures needed to be in the headlines again.

To this end, paleontologist Dave Hone over at his Archosaur Musings blog recently posted “A guide for journalists reporting on dinosaur stories” that deals with some of issues raised here. It’s worth reading.

Science Buzz has also covered science writing issues in previous posts.
How to read/write science news
Bad Science Journalism

SOURCE and MORE INFO
ScienceDaily.com story
Microraptor gui: Bird or Dinosaur
Origin and Evolution of Birds

Feb
08
2010

Measuring the SMM camptosaurus: SMM paleo lab volunteers Becky Huset (left) and Neva Key consult over their ornithischian limb bone measurements for the Open Dinosaur Project.
Measuring the SMM camptosaurus: SMM paleo lab volunteers Becky Huset (left) and Neva Key consult over their ornithischian limb bone measurements for the Open Dinosaur Project.Courtesy Mark Ryan
The Open Dinosaur Project (ODP) allows anyone with an interest in paleontology, and access to skeletal information, scientific publications, or museum skeletons themselves the opportunity to be part of the compilation of an actual scientific paper. Paleontologists Andy Farke, Matt Wedel, and Mike Taylor make up the core ODP team, but only the core. The rest of the team is made up of individuals around the world. The hope is to put together a comprehensive database of information about the dimensions of limb bones (legs, arms, hands, and feet) of ornithischian (bird-hipped) dinosaurs in museums around the world with a goal of “investigating the evolution of locomotion and limb proportions in this group.”

“The Open Dinosaur Project fits very comfortably into that loose coalition of ideas: we’re trying to democratize science, open up data, blog the process, and make sure that the final publications are freely available to the world,” Mike Taylor said during a recent interview with the Brazilian science publication Ciência Hoje On-line.

Putting tape to toe: SMM volunteer Becky Huset measures the metatarsals and phalanx of the musuem's camptosaurus for the Open Dinosaur Project.
Putting tape to toe: SMM volunteer Becky Huset measures the metatarsals and phalanx of the musuem's camptosaurus for the Open Dinosaur Project.Courtesy Mark Ryan
Two volunteers here at the Science Museum of Minnesota got themselves involved with this unique study. Becky Huset and Neva Key both work in the SMM paleo lab, usually hunched over fossils extracting them from rocks or preparing them for display. But recently, the two have spent time out on gallery floor measuring the limbs of some of the museum’s mounted ornithischian dinosaurs.

“We did the Camptosaurus and some cast bones from Stegosaurus from the collections,” Becky said. She added that measurements of the SMM Triceratops were already listed.

Why only ornithischian dinosaurs? Part of the reason was to keep the study somewhat manageable. But ornithischian dinosaurs also have an interesting evolution of locomotion that to date hasn’t been studied in depth. The dinosaur order radiated from a two-legged (biped) form into at least three different four-legged (quadruped) forms including armored dinosaurs (e.g. stegosaurs and ankylosaurs), ceratopsians (e.g. triceratops and chasmosaurus), and various ornithopod types, (e.g. camptosaurs, hadrosaurs, and iguanodontids).

How to measure a scapcoracoid: One of several measuring aids available to project volunteers from the Open Dinosaur Project website.
How to measure a scapcoracoid: One of several measuring aids available to project volunteers from the Open Dinosaur Project website.Courtesy Open Dinosaur Project
In order to aid team members in gathering the proper information, instructions, templates, and other documents are available on the Open Dinosaur Project website. Diagrams explaining ornithischian limb osteology – including each bone’s proper name - are also on the site, as are illustrations showing exactly how to properly measure the dimensions of different bones. For those involved who don’t have access to museum specimens or material in other collections, the team leaders provide lists where prior publications with skeletal information can be accessed and mined for the study.

By last week, the Open Dinosaur Project had acquired nearly 1600 entries, but the results of all this work remain to be seen. The compiled data will be analyzed over the next couple months, and Farke, Wedel, and Taylor plan to begin writing the paper this spring. When completed the study will be submitted for publication in a peer-reviewed journal. If all goes as planned, after publication, the lead researchers will make all the data available online for future studies.

Now that their data has been entered on the ODP site, SMM volunteers Huset and Key will have their names included as contributors, and eligible to be included in the resulting paper.

"We wanted to get the general public excited about and involved in doing “real” science, working in cooperation with paleontologists. There is a great interest out there in paleontology, particularly dinosaurs. It’s amazing how many non-paleontologists read the technical literature! I thought, “Why not harness this enthusiasm?” There have been many people waiting for this sort of opportunity (even if they didn’t know it), and I think the response speaks for itself." – Andy Farke in Ciência Hoje On-line

Becky Huset enjoyed being involved with the project. “[It] sounded like a good idea,” she said. “I like having knowledge that is freely available to everyone, and it was a good way to contribute to a paper. Do some "real" work."

LINKS

Open Dinosaur Project website
Wedel’s & Taylor’s dino-related blog
More about Ornithischian dinosaurs
Osteology (the scientific study of bones)

Feb
08
2010

Viral hemorrhagic septicemia: a fish infected with the virus
Viral hemorrhagic septicemia: a fish infected with the virusCourtesy Dr. Mohamed Faisal
No… not a rock bass (even though it has a red iris). Nor any normal walleye you might be lucky enough to snag. This fish you might not even need to actually catch. It could be floating next to the boat along with most of the other fish in your favorite river, lake, or reservoir. That is if the dreaded VHS continues to spread and strike us deep in the land of 10,000 lakes. Move over zebra mussel, Eurasian milfoil, and the Asian carp, VHS is viral hemorrhagic septicemia and the latest migrant in the spread of invasive species.

Viral hemorrhagic septicemia (VHS) is a virus. It is a small invading critter that can be quite infectious. Not all fish will show obvious signs. Those that do can exhibit hemorrhaging in the eyes, around the fins, or on the gills. Bloating, erratic behavior, bulging eyes, or even lesions could also be present. On the inside, the disease will attack the liver, kidneys, spleen or swim bladder. Those fish that do survive can still be infected and spread the disease. Blood, urine and even the reproductive fluids of infected fish can pass on the virus. Larger fish can get it from eating smaller infected fish.
Fish kill: sights like this are all the more possible with the new viral invader
Fish kill: sights like this are all the more possible with the new viral invaderCourtesy JoelDeluxe

The disease can be wide spread and is known to affect up to 28 different species of fish. Some of the fish kills have numbered in the tens of thousands. Many of our popular game fish are susceptible. Walleye, Northern Pike, Muskellunge, Smallmouth Bass, Perch, Crappies, Bluegills, Sheepshead and many others are on the list. Even some species of shiner bait fish have been found to carry the disease. While deadly for many fish, the disease is of no harm to humans. The warmth of our bodies is too hot for the virus to survive.

The virus has been known for many decades, but until recently was mainly a scourge of European fish farms. Viral hemorrhagic septicemia was first detected in American coastal waters in 1988, among the salmon populations of the Pacific Northwest. Then in 2005, tested fish showed up positive between Lake Huron and Lake Erie, and were confirmed in samples harvested two years earlier. Now, local news just recently reported on a Cornell study that found VHS diseased fish in the bay waters of the Duluth-Superior harbor on the western edges of Lake Superior. Make no mistake… the ‘bleeding fish’ disease is here at our doorstep.

Guests of the inland waterways will be reminded to be vigilant in safe boating and fishing practices by local resource managers. Be mindful not to transport fish, plants, or bait from one water body to another. Keep those live-wells empty, and dry or rinse that boat! It will fall upon all of us to remain vigilant. Let’s not allow this disease to become a crippling blow to our native fisheries. If we do, it is possible that we’ll witness many seasons of massive fish kills.

More good VHS information:
Wisconsin Dept. of Natural Resources

Univ. of Wisconsin Sea Grant

Jan
23
2010

Great Lakes fishing industry endangered

Asian carp
Asian carpCourtesy kate.gardiner
The commercial fishing industry in the Great Lakes, worth more than $7 billion a year, is threatened by Asian carp. Asian bighead (Hypophthalmichthys nobilis) and silver (H. molitrix) carp imported in 1970 to remove algae from catfish farms escaped into the Mississippi River during a flood. Since then they have outcompeted other fish. Along some stretches of the Illinois River, the carp make up 95 percent of the biomass. In December, the State of Michigan filed a lawsuit against the State of Illinois to close of locks between Chicago-area waterways and Lake Michigan.

"We cannot allow carp into the Great Lakes. It will destroy our Great Lakes fisheries, the economy," Michigan Gov. Jennifer Granholm said in a prepared statement." New York Times

Supreme Court denies appeal to protect Great Lakes ecosystem

On Jan 19, 2010, the U.S. Supreme Court turned down Michigan's request to block Asian carp invasion of Great Lakes (Scientific American). The Supreme Court didn't reveal any of the reasoning behind its ruling, which simply read: "The motion for preliminary injunction is denied."

White House appeal

Governor of Michigan, Jennifer Granholm, is "asking for an immediate summit at the White House with the administration to shut down these locks, at least temporarily, until a permanent solution can be found.”

The AP reported the White House response to be:

“The Obama administration clearly understands the urgency of this critical issue, and we look forward to meeting with them on the threat the Asian carp poses to the Great Lakes.” Dayton Daily News