Stories tagged Life Science

Oct
13
2005

Scientists at The Field Museum in Chicago have discovered
a new type of dinosaur,
called Buitreraptor (BWEE-tray-RAP-ter). About the size of a turkey, it was probably covered with feathers and lived in Argentina some 90 million years ago.

Buitreraptor

Buiteraptor is a type of dinosaur known as a dromeosaur., which also includes the famous Velociraptor. Their skeletons are very similar to birds'. In fact, scientists have used them as evidence that birds evolved from dinosaurs-quite possibly from dromeosaurs.

However, there has always been an inconsistency. The earliest known bird is about 150 million years old. The earliest dromeosaurs appeared about 125 million years ago. Kind of hard to be an ancestor if you're younger than your descendents.

But the new fossil changes all that. It's from South America. All previous dromeosaurs had been from North America (or Asia). North and South America split apart some 145 million years ago. So, in order for there to be dromeosuars on both continents, the group must have appeared at least that long ago-which puts them right in the ballpark to be, if not the direct ancesors of birds, then at least very close relatives.

Oct
12
2005

A visitor to this website recently posted this question:

How is evolution proved right? How is there proof of this "chance?" There are many other ways people say the earth was created; which is right? Is there a God that created the world? Or did everyone simply evolve? Whatever you believe, how do you prove yourself right?

Here is the Science Museum of Minnesota's official position on evolution.

That said, "proof" is really the crux of the issue.

All explanations of the Earth's creation other than evolution basically say that life is too complicated to explain by natural processes; something outside of nature must have created it. The only way to prove or disprove an idea like that is to look outside of nature. And once you go outside of nature, you're no longer doing science.

Science is a way of looking at the world, asking questions about nature and looking for answers in the natural processes around us. It works on one simple rule: show us the evidence! Show us an experiment in the lab or an observation in nature, but you have to point to something real that can be seen or measured. And then you have to come up with an explanation for what you've seen. You have to test your explanation by doing another experiment or making another observation that supports you. And if the results don't match, you know your explanation was wrong.

In science, a theory is an explanation that accounts for all the evidence. Atomic theory explains how matter works. Gravitational theory explains how gravity works. And evolutionary theory explains how life has changed over time.

Evolution is both a fact and a theory. The word has two meanings. First, it means "the history of life on Earth." And there's no denying that life has changed over the last 500 million years-go to the Dinosaurs and Fossils Gallery and see for yourself. But evolution also means "the explanation of HOW those changes have occurred." Scientists use the word theory for explanations that account for all the evidence.

And there is a lot of evidence for the theory of evolution. Every fossil that's ever been found; every animal that ever lived; every cell in your body-all of these support evolution. Scientists have been poking and prodding and testing the theory for 150 years, and have written tens of thousands of papers on the subject. Evolution is the best explanation we've ever had for the history of life on earth. (In terms of experiments and observations, it has been said there is more solid evidence for evolutionary theory than for atomic theory-and no one doubts the existence of atoms!)

Evolution happens every day, all around us. The bird flu that's been in the news is an example of evolution in viruses. New breeds of farm plants and animals are examples of evolution. And every baby that is born today will inherit traits from its mother and father, and so also be an example of evolution in action.

Science is really good at explaining WHAT and HOW: what our bodies are made of, how they work, how we evolved. But one thing science cannot do is explain WHY. Why are we here? What is our purpose? What is life's meaning? For that, you need religion.

OK, so what is evolution?
Evolution, by the most basic definition, is the profound, ceaseless change in life forms through time.

Charles Darwin and Alfred Wallace were the first scientists to call this change in life over time "natural selection," although many others have contributed to the idea. (Changes in the theory of evolution have been made since Darwin's original proposal, yet his main theory stands firm.)

The theory of natural selection is based on three principles:

  • Organisms produce more offspring than can survive and reproduce.
  • Those that do survive tend to be better adapted to local environments.
  • Most adaptations are genetic, so they can be passed from parent to offspring.

Generation by generation, organisms that are better adapted to their environment in some way survive to pass on their advantageous qualities.

Evolution is not purposeful: it does not work toward a specific end or create better or worse organisms. Species evolve by adapting to particular niches in their environments, but the genetic mutations that lead to these adaptations occur by chance. An organism cannot will itself to mutate in a beneficial way. If its niche disappears, the species may become extinct or it may adapt to new conditions, but the failure to do so does not imply some kind of defect.

Evolution does not occur "for the good of a species." It operates at the level of individual organisms over many generations. A whole population does not simultaneously evolve a new trait; instead, the new trait evolves in one or a few organisms, which pass it on until the population is dominated by organisms having that trait.

Even more evidence of evolution
As humans, we share features with all living life forms, past and present. The more specific these features are, the more recently scientists think they evolved. For example, fingernails-a feature we share with all primates-evolved 30 million years ago. We have the same basic anatomical plan as all other vertebrates, which evolved 500 million years ago. And our cells'ability to use oxygen goes all the way back to our relationship with plants, fungi, and bacteria, which evolved over 1,000 million years ago.

Here are other examples of evidence for evolution:

  • Some animals have organs that serve no purpose but have a function in other species. Such a structure is referred to as vestigial. Whales, for instance, possess useless pelvic bones left over from their land-dwelling ancestors. Fossil whales are found with tiny limbs that became increasingly unimportant.
  • Many closely related species live in proximity to one another but are separated by a geographical barrier. (It was observations like this on the Galapagos Islands that helped Darwin formulate his theory of natural selection.) For example, two similar species of fish live separated by Central America: one in the Gulf of Mexico, and the other in the Pacific Ocean. They evolved when the Isthmus of Panama formed and separated their common ancestor's population into two groups. If the fish had not evolved after they were separated, the same species would live on both sides of the isthmus. And if they hadn't descended from a common ancestor, they wouldn't be so similar.
  • As we develop more types of antibiotics, new resistant strains of bacteria evolve through natural selection. Many crop pests have also evolved strategies to cope with our use of pesticides. Some species of grass have even evolved ways of thriving on industrial waste.
  • Through artificial selection, humans have developed new plants and animals. By manipulating genes, we have obtained many different types of crop plants-some produce greater yields, some produce higher concentrations of their own natural pesticides, and some are more resistant to drought. From a very basic canine type, we developed many different breeds of dogs over the last few thousand years. Artificial selection is somewhat analogous to natural selection; the difference is in the selective force-humans, instead of nature.
  • All multi-celled creatures share distinct genes for developing body plans (like plans for limbs, eyes, etc.). These genes, called homeotic genes, are incredibly similar in all animals, even among animals as different as fruit flies and chimpanzees.
Oct
10
2005

It's in the news. People are dying from a relative of the 1918 Influenza virus half a world away, and scientists fear it may be the next pandemic. Sounds like science fiction, or the latest box-office smash, right? Unfortunately, it's real, and is happening right now.

chickens: (Photo courtesy Laura Hadden)
chickens: (Photo courtesy Laura Hadden)

In Southeast Asia, a virus known as avian influenza or avian flu has the potential to spread and kill humans with terrifying speed. Avian flu is also known as H5N1 for the proteins that bind, infect, and destroy its host cell to thrive. Chickens can die within hours of exposure, swollen and hemorrhaging, but it is just as lethal to mammals from lab mice to tigers. The virus has decimated bird flocks in 11 countries mostly in Asia, and has killed 62 people (half the known cases) to date, with highest fatalities occurring in Vietnam, Cambodia, and Thailand. So far, nearly all people infected contracted the sickness directly from infected poultry and at this point there is no confirmed evidence of efficient human-to-human transmission. However, health authorities fear that the H5N1 strain will likely mutate into a pathogen easily passed between humans if it continues to persist in the environment. If that happens, and authorities believe it's only a matter of time, the world could face a catastrophic pandemic.

Many health organizations and governments are stockpiling a drug (Tamiflu) to protect against this potential pandemic, but scientists are reporting that a strain of H5N1 avian flu virus is showing resistance to the antiviral drug. Scientists are working to avoid this disaster by detecting changes in the evolving H5N1 virus. As a first step, scientists have rebuilt the 1918 flu-a disease that killed as many as 50 million people-from pieces of genetic material retrieved from the lungs of people who died 87 years ago. Gene-swapping experiments are starting to give scientists some clues in the lab. When small substitutions were made, the reconstructed virus could no longer replicate in the lungs of mice, kill animals, or attach itself to human lung cells.

So far H5N1 has not yet learned the trick of racing from person to person like the ordinary flu and maybe never will. Nevertheless, experts fear that the risk could materialize and are urging the world to prepare for the worst.

United Nations Food and Agriculture Program

NPR Health and Science Report

Oct
07
2005

What are your thoughts about the reconstruction of the 1918 flu virus?

  • Richard H. Ebright, a microbiologist at Rutgers University, has serious concerns and believes "there is a risk verging on inevitability, of accidental release of the virus; there is also a risk of deliberate release of the virus."
  • Dr. Anthony S. Fauci, Director of the National Institute of Allergy and Infectious Diseases (which helped pay for the reconstruction work), says that the board "voted unanimously that the benefits outweighed the risk that it would be used in a nefarious manner."

What do YOU think?

Aug
05
2005

On Wednesday, a group of scientists from Seoul National University unveiled a black and white Afghan hound named Snuppy that is genetically identical to its three-year-old "father."

Snuppy is the result of a process that involved transferring 1,095 canine embryos into 123 surrogate mothers. Only three successful pregnancies occurred. One foetus miscarried but two others were delivered; Snuppy was born on April 24 and his "brother" died from pneumonia after 22 days.

Snuppy is the latest in a series of animal cloning attempts since Dolly, the sheep cloned in 1997. Researchers have since cloned mice, cats, goats, pigs, mules, horses and deer. Dogs, however, are the most challenging of all mammals to clone, because it's difficult to acquire mature eggs. Snuppy's success makes many scientists believe that they have most of the key techniques necessary to clone humans.

The response to Snuppy? Anti-cloning activists are pushing even harder for a worldwide ban on human cloning. "Because this again shows that reproductive cloning is unsafe and inefficient, we call for a worldwide ban on human reproductive cloning, which is also unethical," says Gerald Schatten, at the University of Pittsburgh School of Medicine. Others feel optimistic that Snuppy's creation brings medicine one step closer to finding breakthrough treatments for currently-incurable human diseases. "Bring me human eggs, the necessary social consensus and legal permission and I can get you your replica within a year," said Park Se-Pill, a senior researcher of Maria Biotech and a top cloning expert.

Many diseases, for example, like diabetes, cancer, heart ailments, and problems in hips and joints, are similar in dogs and humans.

Jul
19
2005


Microscopic image of turkey muscle cells grow in culture.: Image Credit: University of Maryland

A recent article in the journal Tissue Engineering proposes two ways for laboratories to grow artificial meat. One method would be to grow cells from common livestock animals like cows or chickens in large flat sheets. The thin sheets would then be stacked to resemble meat. The other proposed method would be to grow muscle cells on small beads that stretch with small changes in temperature. The tissue produced could be used to make processed meat such as hamburgers or chicken nuggets.

The research is being done at the University of Maryland and is based on experiments NASA has conducted to grow artificial meat for space missions.

But why produce artificial meat commercially?

One reason would be to make meat healthier for the consumer. Meat contains a lot of omega-6 fatty acid, which is good, but not in large amounts. The omega-6 fatty acids could be replaced with omega-3 fatty acids which are more beneficial.

Another reason is that raising livestock has a huge environmental impact. Livestock require millions of gallons of water, large amounts of land, and produce huge amounts of waste. The use of artificial meat would help to protect the environment by potentially reducing the number of livestock needed to meet the demands for meat.

Further, the production and consumption of meat has many additional potential issues including meat-borne pathogens and contaminants, antibiotic-resistant bacteria due to the routine use of antibiotics in livestock, and inhumane treatment of farm animals.

The author of the paper, University of Maryland doctoral student Jason Matheny, sees so many advantages in the production of artificial meat that he joined several other scientists in starting a nonprofit, New Harvest, to advance the idea.

Would you eat artificial meat?

Jul
01
2005

Last year nearly 28,000 Great White Pelicans who make the islands of Chase Lake at the Chase Lake National Wildlife Refuge in North Dakota their nesting grounds abandoned the rookery without warning. They left behind thousands of eggs and chicks that did not survive.

The pelicans began returning this past April. Chase Lake Wildlife officials estimate that 18,850 pelicans have returned to the 4,385-acre refuge this year. In 2003 there were 29,494 birds on the islands, but the birds left before they could be counted last year. Officials are hoping that the pelicans will remain until September raising their young.

Why they left in the first place remains a mystery, perhaps one that we may never solve. Was it a natural correction to overcrowding on the islands? Officials from the refuge checked air, water and soil quality on the islands as well as investigated possible diseases, predators and other potential factors. Nothing stands out as a reason for the bird's sudden departure.

Why do you think the birds left so suddenly?

Jun
21
2005

Natural resource officials in Minnesota and Iowa are advocating for the construction of two fish barriers on the Mississippi River that they hope willl stop the upstream migration of Asian carp.

These barriers, which would be placed below lock and dam 14 or 15 (just north of Davenport, Iowa) and lock and dam 11 (just north of Dubuque, Iowa), might use bubbles and sounds to stop the fish from entering the open locks. The fish could be directed into pools where commercial fishermen could harvest them. (Similar barriers are already used on a smaller scale to keep fish away from water intake pipes at power plants.) Minnesota Department of Natural Resources employees are looking at a variety of different technologies, trying to find one that's as selective as possible. The idea is to find something that will deter the carp, but not the paddlefish and other species that ecologists want migrating up the river, many of which are threatened or endangered.

How big is the invasive carp problem? That's a little unclear. So far, two species of the fish--bighead and silver carp--have escaped from southern fish farms and moved north along the Mississippi and its tributaries. A third species, black carp, has been caught in several areas, but scientists don't know if it's reproducing. One bighead carp was caught in Lake Pepin (south of the Twin Cities) in the fall of 2003, but no others have since been reported.

But the Upper Mississippi is one of the most pristine of American rivers, and officials are anxious to keep it that way.

Silver and bighead carp can reach more than 50 pounds, and out-compete native species for food such as plankton. Silver carp are also dangerous to recreational boaters and water-skiers, as they jump out of the water when disturbed; they've injured people and damaged equipment.

The University of Minnesota's Bell Museum of Natural History has an invasive carp feature on their "Hot Topic" website.

The Star Tribune has a special feature on invasive species in the Great Lakes.

Jun
21
2005

According to the Minnesota Department of Health, there were 1,023 recorded cases of Lyme Disease in Minnesota in 2004. This number is more than double the 473 cases reported in 2003. The increase could be the result of mild winters that have allowed the deer and field mice that the deer ticks feed on to survive the winters in greater numbers.

Lyme disease is a potentially serious bacterial infection that can result in flu like symptoms and if untreated can lead to arthritis, nervous system problems and persistent fatigue. Antibiotic treatment is effective, especially if treatment is begun during the early stages.

The disease is spread when an infected deer tick attaches itself to a person. Not all deer ticks are infected with the bacteria, so not all deer ticks will transmit the disease. In order for the infection to be transferred from an infected deer tick to a person, the tick needs to be attached for at least 24 hours.

To protect yourself from contracting Lyme disease you should avoid tick habitats, if possible. If avoiding tick habitats is not possible, use a tick repellent containing DEET and wear light-colored clothes so you can more easily spot a deer tick on you. Check for ticks after being in their habitats and if you find a tick on you, remove it as soon as possible.