When you look at something, whether it’s a tomato or your backpack or your best friend, your eyes send a signal about that object to your brain. Different regions of the brain process the information your eyes send. Cells in your brain called neurons are responsible for this processing.

The fMRI brain scans could generally match electrical activity in the brain to the basic shape of a picture that someone was looking at—such as the circle of the moon here. But there’s no way for fMRI to pick up enough detail to figure out whether so

Photodisc

Like cells anywhere else in your body, active neurons use oxygen. Blood brings oxygen to the neurons, and the more active a neuron is, the more oxygen it will consume. The more active a region of the brain, the more active its neurons, and in turn, the more blood will travel to that region. And by using a technology called functional magnetic resonance imaging, or fMRI, scientists can visualize which parts of the brain receive more oxygen-rich blood—and therefore, which parts are working to process information.

An fMRI machine is a device that scans the brain and measures changes in blood flow to the brain. The technology shows researchers how brain activity changes when a person thinks, looks at something, or carries out an activity like speaking or reading. By highlighting the areas of the brain at work when a person looks at different images, fMRI may help scientists determine specific patterns of brain activity associated with different kinds of images.

The California researchers tested brain activity by having two volunteers view hundreds of pictures of everyday objects, like people, animals, and fruits. The scientists used an fMRI machine to record the volunteers’ brain activity with each photograph they looked at. Different objects caused different regions of the volunteers’ brains to light up on the scan, indicating activity. The scientists used this information to build a model to predict how the brain might respond to any image the eyes see.

In a second test, the scientists asked the volunteers to look at 120 new pictures. Like before, their brains were scanned every time they looked at a new image. This time, the scientists used their model to match the fMRI scans to the image. For example, if a scan in the second test showed the same pattern of brain activity that was strongly related to pictures of apples in the first test, their model would have predicted the volunteers were looking at apples.

Using the model, the scientists successfully used the brain scan to predict which photo one volunteer was looking at 92 percent of the time. For the other volunteer, the scientists were correct only 72 percent of the time.

But don’t count on reading your friend’s mind next time she has a secret to tell. While the results are intriguing, mind-reading brain scans won’t be on the horizon anytime soon, the researchers note. When volunteers viewed a much larger number of photos—a total of 1,620 pictures—the scientists had a much more difficult time predicting what the volunteers were looking at, based on the brain scan alone. In this situation, the scientists chose the correct brain scan–photograph pair only half the time with one volunteer and only a third of the time with the other—Jennifer Cutraro

Power Words

From The American Heritage® Student Science Dictionary, The American Heritage® Children’s Science Dictionary, and other sources.

neuron A cell of the nervous system. Neurons, also called nerve cells, send and receive signals in the form of electric impulses from other nerve cells. A bundle of nerve cells is called a nerve.

cell The most basic part of a living thing, made up of a jelly-like substance called cytoplasm that is enclosed by a thin membrane. The cells of plants and animals have a nucleus, which contains the genes and other structures. The cells of green plants and some algae have chloroplasts, which is where photosynthesis takes place.

brain The main part of the nervous system in vertebrates that controls all body activities, such as breathing and walking. In humans, the brain is the center of speech, memory, thought and feeling. The brain is protected by the bones of the skull and is connected to the spinal cord.

fMRI fMRI stands for functional magnetic resonance imaging. fMRI is largely a research technique that uses MRI scanners to visualize activity in the brain over time. MRI itself produces non-moving, but highly detailed images of the molecules that make up a substance, especially the soft tissues of the human body. It works by taking advantage of nuclear magnetic resonance. MRI is used in medicine to diagnose disorders of body structures that do not show up well on x-rays.

Copyright © 2002, 2003 Houghton-Mifflin Company. All rights reserved. Used with permission.

Going Deeper:

Callaway, Ewen. 2008. Pick a photo, any photo. Science News 173(March 15):173–174. Available at http://www.sciencenews.org/articles/20080315/note14.asp .

A team of scientists at the University of Utah in Salt Lake City recently discovered that alligators use their breathing muscles for a second job: to shift their lungs around inside of their body. This helps the animals move up and down in water by allowing them to control their buoyancy, or which parts of them float and which parts sink. To dive, they squeeze their lungs toward their tail. This tips a gator’s head down and prepares it to plunge. To surface, the alligators move their lungs towards their head. And to roll? They use muscles to push their lungs sideways.

Alligators use muscles to pull their lungs in different directions. Moving the position of their lungs helps alligators control their buoyancy, or the way they float in the water. This control helps them move smoothly through water, researchers say.

L.J. Guillette, University of Florida

“The big picture is that lungs are probably more than just breathing machines,” says T.J. Uriona. He’s a graduate student and one of the scientists from Utah who discovered how alligators use muscles to move their lungs.

Alligators have some breathing muscles that people don’t have. A large muscle connects the alligator’s liver to the bones at its hips. When this muscle pulls the liver down and towards the tail, the lungs get stretched down too. Then, more air flows into the lungs. And when the muscle relaxes, the liver slides up and the lungs get squeezed, pushing air out.

What’s puzzling is that when this liver-to-hips muscle doesn’t work, alligators can still breathe well. That led Uriona and his colleague C.G. Farmer to first study how alligators might use this and other muscle groups surrounding their lungs.

To test these muscle groups, the researchers placed electrodes in the muscles of a group of young alligators. Electrodes are tools scientists can use to measure the electrical signals that muscles make when they working. The electrodes showed that alligators clench four groups of muscles when they dive. These include the muscles that pull the lungs back and toward the animal’s tail when they tighten.

That finding was what made Uriona wonder whether pulling the lungs back helps the alligator dive into the water.

To find out, he and Farmer taped lead weights to the animals’ tails. This made it harder for the animals to dive nose first. The electrodes showed that with weight added to their tails, the muscles needed to work even harder to pull the lungs far back toward the tail.

What would happen if the weights were instead taped to the animals’ noses? Adding weight to the front of the body should make a downward dive easier than adding weight to the back of the body. And that’s just what the electrodes showed. The muscle groups didn’t have to work as hard.

And for a rolling alligator? Data from the electrodes showed the breathing muscles on only one side of the body tightened. The muscles on the other side remained relaxed. This squeezed the lungs to one side of the body, making that side rise up in the water.

Unlike aquatic animals like fish and seals, alligators don’t have fins or flippers to help them move smoothly in the water. But somehow, they still manage to sneak up silently on prey while moving through the water.

Uriona says using the lungs for motion might have evolved as a way for gators to surprise unsuspecting prey. “It allows them to navigate a watery environment without creating a lot of disturbance,” he says. “This is probably really important when they are trying to sneak up on an animal but they don’t want to create ripples.”

Power Words

From The American Heritage® Student Science Dictionary, The American Heritage® Children’s Science Dictionary, and other sources.

electrode A piece of carbon or metal through which an electric current can enter or leave an electric device. Batteries have two electrodes, positive and negative.

buoyancy The upward force on an object floating in a liquid or gas. Buoyancy allows a boat to float on water.

Copyright © 2002, 2003 Houghton-Mifflin Company. All rights reserved. Used with permission.

Going Deeper:

Milius, Susan. 2008. Gator aids: Gators squish lungs around to dive and roll. Science News 173(March 15):164-165. Available at http://www.sciencenews.org/articles/20080315/fob5.asp .

Particularly challenging are the crimes that involve poaching—taking animals from the wild that are protected by law. Poachers can make a lot of money selling meat, tusks, fur, fins, and other parts of protected animals.

Federal inspectors took this suitcase from a traveler passing through Miami’s airport. Inside were poached shark fins and seahorses that NOAA enforcement officers later sent to researchers at Nova Southeastern University in Florida for identification.

R. Horn/Nova Southeastern Univ. Oceanographic Ctr.

Poaching can devastate even large wildlife populations if too many animals are taken in any year or from any area. The problem becomes even more serious when a species is endangered. Then, losing even a few animals can make it harder for the species to survive.

What’s really bad is that poaching creates an unfortunate cycle: As the animals become more rare, their parts become more valuable. So, poachers earn even greater rewards for their collection of protected species.

Now, scientists are helping fight back. Using the genetic material DNA, they are finding ways to clinch hard-to-solve cases involving a wide range of creatures, from elephants to seahorses.

If you’ve ever read a legal thriller or watched shows on TV such as CSI: Crime Scene Investigation, you know that DNA plays a big part in solving human crimes. The molecule appears in every cell. Like fingerprints, DNA is unique to every person. So, by analyzing DNA in blood, saliva, or hair left behind at the scene of a crime, detectives can identify criminals and victims.

When authorities find poached animal parts, they aren’t usually interested in identifying individual creatures. Instead, they want to know what species the parts belong to. That may not be obvious if all you have is a bit of meat, bone, or perhaps a fish fin. DNA can also prove helpful in figuring out where an animal came from. That’s because members of one local group of animals tend to share more DNA in common with each other than they do with more distant groups of their species.

Based on concepts such as these, scientists are developing new tests to untangle complicated webs of animal-related crime.

Tusk trackers

Elephants have been particularly devastated by poachers in recent decades. Between 1979 and 1987, poachers killed hundreds of thousands of wild elephants in Africa and Asia. This poaching reduced the animals’ numbers by more than half, says Samuel Wasser, director of the Center for Conservation Biology at the University of Washington, Seattle.

The motivation? Ivory. Elephant tusks are made of the hard, white material, which has long been used in jewelry and art, among other applications.

Poaching slowed down after an international ban on the ivory trade was passed in 1989. For a variety of reasons, however, the practice started creeping up again a few years later. By 2005, Wasser says, “the illegal ivory trade had come back with a vengeance.”

Even though it’s against the law to buy newly harvested ivory, people prize it so much that some are willing to buy it illegally. Such sales are said to be on the “black market.” In the past few years, the black-market price of ivory has quadrupled to about $850 per kilogram (2.2 pounds). A tusk can weigh 11 kg (24 pounds) or more.

Tens of thousands of elephants are dying each year as a result. There are fewer than 500,000 elephants living in the wild today.

Elephant poaching is hard to squelch because hunters often work in remote areas. Middlemen gather tusks from a variety of places. And well-hidden shipments follow complicated routes to destinations far from where they started. A single shipment can contain hundreds of tusks, thousands of pounds, and many millions of dollars worth of ivory.

Authorities intercept just 10 percent of these shipments, Wasser estimates. But even when officials retrieve the ivory, they usually don’t know where it came from.

To answer this question, Wasser has been looking for clues in elephant DNA. First, he collected elephant dung from 28 regions in 16 countries throughout Africa. He analyzed DNA in the dung samples. Then, he used the results to start mapping connections between an elephant’s DNA and its home range. Finally, he used statistics to fill in the blanks (see “Gene Sleuths Track Down Ivory Sources”).

“I’ve been working for 8 years on building this map,” Wasser says. “It has taken a while, but we’ve done it.”

But poachers trade tusks, not poop. And getting the genetic material out of ivory is more difficult. That’s because the outside of a tusk is made of dead cells, while the DNA is in living cells on the inside of the tusk. But smashing or drilling into the tusk destroys the DNA.

To overcome this problem, Wasser developed a way to extract DNA from ivory under supercold conditions. With liquid nitrogen, he was able to freeze the material. Then, he used a magnet and alternating magnetic fields to grind up the sample without destroying the DNA.

Using the technique, Wasser helped trace the origins of one of the largest ivory seizures ever made. The shipment, which contained 13,000 pounds (5,900 kilograms) of ivory, was seized in Singapore in 2002.

Wasser’s analysis showed that nearly all the seized ivory had come from a small region in Zambia. It was an important discovery because wildlife officials originally thought the shipment’s contents had come from many different places.

Investigators can use genetic techniques to trace tusks or their ivory back to the population of elephants from which they were poached.

Photodisc

Findings like these are helping authorities narrow the hunt for elephant hunters.

“DNA can really help us stop the [ivory] trade at its source,” Wasser says. “For the first time, we don’t just have information about shipping and receiving, but about where the ivory comes from. This has completely changed the way law enforcement thinks about how to deal with these cases.”

Something’s fishy

Authorities are also getting better at nabbing shark poachers, thanks to Mahmood Shivji, a conservation geneticist at a shark conservation consortium at Nova Southeastern University’s Oceanographic Center in Dania Beach, Fla. Trained as both an oceanographer and geneticist, Shivji is now a DNA detective of the sea.

There are more than 400 species of sharks in the world’s oceans, Shivji says. Fishermen kill about 50 of those fish species for their fins, which people eat. The fins of some species are especially valuable. Sometimes sharks are also killed for their meat.

As a result of hunting pressures, shark numbers have dropped 70 percent in the past 2 decades. Many populations are now threatened and a few are even endangered.

It is legal to fish for most sharks, especially if the fish will be sold for meat. However, most sharks are killed for their fins—not meat. Fishers haul in the animals, slice off their fins and then throw the rest of the still living shark back in the water to slowly die.

It’s gruesome. It’s also a tremendous waste of majestic animals that help keep ocean ecosystems healthy. That’s why it is now illegal to kill a shark in the United States—unless the entire animal is kept for sale. Any ship containing fins without the rest of the animal is automatically guilty of shark “finning”, an illegal activity (poaching).

King Diamond II. Although it had no fishing gear on board, it was carrying 32 tons of rotting shark fins. Nearly all had been neatly bundled into roped bales. Shown here is j” />

On Aug. 23, NOAA took possession of the “fishing boat” King Diamond II. Although it had no fishing gear on board, it was carrying 32 tons of rotting shark fins. Nearly all had been neatly bundled into roped bales. Shown here is j

U.S. Coast Guard

To protect sharks from poachers, Shivji says, authorities must first figure out which species are being hit hardest. But that’s hard to do when the only evidence is fins—which pretty much look alike, regardless of which shark species they came from.

“Markets are supplied from all over the world,” he says. “No one is keeping track of whether populations in certain parts of the world are being overfished relative to other populations.”

With those two goals in mind, Shivji started by studying DNA from 70 shark species, including all the varieties that end up in the fin trade. He found a small region of DNA that differs between species. Then, he created a simple test that identifies species on the basis of DNA taken from a meat or fin sample.

Next, Shivji found a different region of DNA that varies between members of the same species. He developed another test that identifies whether a sand tiger shark, for example, came from the northwest Atlantic, the southwest Atlantic, Australia, or South Africa. Finally, he combined the two tests.

The biggest advantage of Shivji’s technique is that it spits out results quickly. In just 2 days, he says, he and his team can identify the sources, by geography and species, for 50 fins.

Right now, the rapid tests can reliably identify 30 shark species. And they can distinguish between geographic populations of two of those species—sand tiger sharks and porbeagle sharks.

Shivji is working on incorporating more groups into the tests. And he wants to make the process even faster by eventually replacing much of the work that humans do with robotic technologies.

This Asian market boasts a range of shark fins sold by size and type. A recent estimate indicates that some 40 million sharks are harvested each year for their fins, which would translate into an estimated 1.7 million metric tons of dead sharks.

Shelley C. Clarke/Imperial College London

The technique has already helped solve a number of suspicious cases for the National Oceanic and Atmospheric Administration. NOAA’s Office for Law Enforcement is responsible for inspecting fishing boats that enter U.S. ports. Shivji is also working on cases in foreign waters and helping train foreign colleagues.

As the tests get better and faster, word is spreading that it might not be so easy to get away with shark poaching anymore.

“Now, fishermen can’t say, ‘They’re never going to be able to tell the difference’” between legal and illegal catches, Shivji says. This “is having a positive impact on reducing the amount of illegal activity.”

It usually takes a long time for basic research to make an impact in the real world, Shivji adds. But animal-DNA detective work has quickly made the transition from science lab to crime lab. Scientists are now doing similar work to protect seahorses, seals, and other animals.

If the world’s poaching victims could talk, they would probably thank these scientists for their detective work.

Going Deeper:

Additional Information

Word Find: Poach and Get Caught

The research team was using NASA’s Swift spacecraft to study a galaxy called NGC 2770. They had aimed the spacecraft’s X-ray telescope at a recently discovered supernova. Supernovas are dramatic explosions that happen when a really big star (as least eight times as big as our sun) runs out of fuel. Exploding stars release a lot of energy, much of it in the form of X rays.

Without actually looking for it, astronomers found the supernova SN 2008d through X-ray observations. This is the first time scientists have observed a star shortly before it showed any evidence of exploding. Two other supernovas labeled here were found i

A. de Ugarte Postigo/ESO et al., Dark Cosmology Centre/Univ. of Copenhagen, Instituto de Astrofísica de Andalucía (CSIC), and Univ. of Hertfordshire

Just as the telescope began observing the target supernova, the spacecraft recorded a fresh batch of X rays coming from another region in the same galaxy. The X-ray burst lasted for about 7 minutes.

Although no supernova was visible, these scientists suspected they had just witnessed the beginning of a star undergoing such a catastrophic explosion. Using the Gemini North telescope on the Hawaiian mountain Mauna Kea, the researchers then took another look at the same spot in the sky as where the X-ray burst had been. The region is now called SN 2008d. There they saw a visible-light display, which confirmed that a supernova had indeed occurred.

Astronomers usually can’t spot supernovas until the stars send out large amounts of visible light. By then, however, key information about early stages of the explosive process has vanished.

In the case of SN 2008d, the energy and length of the initial release of X rays suggest that the star was compact. Also, it hurled out lots of gas—called a stellar wind—from its surface before it went supernova.

For decades, scientists predicted that supernovas would send off X rays right before exploding. Now they finally have evidence that they were right.

The new discovery suggests that astronomers might be able to use wide-angle X-ray telescopes to catch the very beginnings of hundreds of supernova explosions each year.

Going Deeper:

Cowen, Ron. 2008. Supernova outbreak: X rays signal earliest alert. Science News 173(March 8):148. Available at http://www.sciencenews.org/articles/20080308/fob3.asp .

Sohn, Emily. 2007. A great ball of fire. Science News for Kids (May 16). Available at http://www.sciencenewsforkids.org/articles/20070516/Note2.asp .

______. 2006. Dead star exploding. Science News for Kids (Aug. 9). Available at http://www.sciencenewsforkids.org/articles/20060809/Note2.asp .

______. 2006. Spotlight on an exploding star. Science News for Kids (March 8). Available at http://www.sciencenewsforkids.org/articles/20060308/Note3.asp .

Shoppers can now buy fruits and fruit juices filled with the flavors of rainforests, distant mountainsides, and tropical islands. With names like açaí (pronounced ah-SIGH-ee), mangosteen, pomegranate, noni, and goji berries, exotic fruits are showing up in growing numbers. Many of these fruits are also used as ingredients in a variety of food products, from granola to ice creams to smoothies.

In the United States, it is illegal for companies that sell products made from these fruits to make health claims about them. But that doesn’t stop magazine articles and health food proponents from doing so. And many now claim that the fruits in some of these products will fight cancer, cure heart disease, strengthen the immune system, and help people live longer, among other benefits.

Based on such claims, these natural products have been dubbed “superfruits.”

Pomegranates, along with other exotic superfruits, are thought to be exceptionally nutritious.

Fir0002/Wikipedia

In 2007, Americans spent tens of millions of dollars on dietary supplements and foods containing superfruits, according to SPINS, a natural-products market-research firm. From 2006 to 2007, sales of goji berries, for instance, skyrocketed 75 percent. Sales of pomegranate products rose by more than 60 percent. And products containing açaí rose 50 percent.

But are mangosteens and goji berries really better for you than apples and oranges?

Companies that add superfruits to their products are funding studies that aim to establish how healthful they are. But many independent nutritionists are skeptical that these foods have extra nutritional value. The only thing that’s really special about superfruits, they argue, may be their price. Owing to the long distances they must travel to reach U.S. kitchens, these exotic fruits usually cost considerably more than local produce.

Right now, “there’s no science that these [exotic superfruits] are associated with better health,” says David Katz, director of the Yale-Griffin Prevention Research Center in New Haven, Conn. “It doesn’t mean [the companies] are wrong. The fact is, there’s no proof that they’re right.”

Definition of super

Superfruits are not the first foods to earn a “super” label. The term has also been used to describe a variety of more ordinary foods, including blueberries, dark chocolate, spinach, and certain types of tea.

Superfood is not a scientific term. But foods that have gained the “super” prefix tend to contain a high concentration of substances called antioxidants (see sidebar: “What Are Antioxidants?”). These chemical compounds may protect people from diseases and aging by limiting certain chemical reactions that happen naturally. But if those chemical reactions become excessive, they can cause damage to the body.

Scientists now think that eating a wide variety of plant-derived foods can make us healthier and less likely to develop certain diseases by boosting the body’s natural antioxidant defenses.

“There are lots and lots of studies that show that antioxidants do contribute to health,” says Jeffrey Blumberg, director of the U.S. Department of Agriculture (USDA) Antioxidants Research Laboratory at Tufts University in Boston.

To lure health-conscious consumers, advertisers often claim that superfruit-filled foods contain extra high levels of antioxidants. One way to measure antioxidant content is to grind up a food and put it in a test tube with free radicals. The more free radicals disabled, the scientists assume, the more plentiful and powerful the antioxidants.

Using such tests, a company called POM Wonderful found that its 100 percent pomegranate juice contained more antioxidants, per ounce, than did any of a dozen beverages made from other fruits, including blueberry, grape, and açaí. The next nearest competitor, red wine, had 17 percent less antioxidant activity than pomegranate juice did.

The Web site for Sambazon, a company that makes products containing açaí, says that this fruit has 30 times as many antioxidants as an equivalent quantity of red wine and 50 percent more antioxidants than an equal amount of pomegranate.

Claims such as these are confusing and conflicting because tests that measure antioxidant levels are unreliable, Blumberg says. Results depend on which parts of the fruit scientists grind up, for one thing. In fact, related tests sometimes produce opposite results. And when different labs do the same test they will sometimes come up with different numbers.

Nutritionists recommend eating a wide variety of fruits and vegetables.

iStockphoto

Another problem is that what happens in a test tube is so simple that it might not predict what will happen in more complex environments, such as the human body. Indeed, certain phytochemicals might never even get into our bloodstream after we eat them, notes Will McClatchey, a botanist at the University of Hawaii, Manoa.

“Some [antioxidants] might be beneficial for us,” McClatchey says. “Some might not. Just because something tests out in a lab to be an antioxidant doesn’t mean it will continue to be an antioxidant when it passes through the digestive tract.”

Health claims

Partly in response to criticisms like these, superfruit scientists are now doing studies in both animals and in people. One goal is to prove that eating these fruits contributes to better health.

Some industry studies have yielded encouraging results. POM Wonderful, which has spent $23 million on pomegranate research over the past decade, has evidence that a daily cup of the company’s pomegranate juice raises antioxidant levels in the bloodstream. Its studies also suggest that drinking the juice protects against heart disease and certain types of cancer.

Similarly, studies funded by a company called Tahitian Noni International have found that drinking noni juice reduces concentrations of certain free radicals in the blood. Early evidence also suggests that the juice might help athletes run longer distances without getting as tired as they normally do, says Brett West, who directs research for the company.

Açaí berries, which grow in Brazil, must be ground up in order to extract the juice.

Decio Horita Yokota/Wikipedia

Studies like these add to a long history of medicinal uses for natural products in traditional cultures. The açaí fruit, for one, which grows only on palm trees in the Brazilian Amazon, has been used to treat fevers. Goji berries, which grow in China and Tibet, have been used to reduce inflammation and improve eyesight. And pomegranates, which are native to Iran and India (but now also grow in California), are sometimes eaten to relieve digestive distress.

Still, there are no large, long-term studies that clearly link any exotic fruits with better health. And nutritionists worry that people are too easily drawn in by whatever’s new and different. All the studies that do show health benefits of certain fruits were sponsored by companies that sell them, and most of the studies lasted only a few days or months.

“It is much easier to ascribe a magical or health property to goji or açaí or chasteberry than to an apple or orange because we already know about apples and oranges,” Blumberg says. But apples, oranges, and other ordinary fruits also contain plenty of vitamins, minerals, and antioxidants.

It can’t hurt to add superfruits to your diet, adds David Grotto, a Chicago-based dietician and author. He regularly makes açaí smoothies and rice pudding with goji berries, among other exotic menu items, for his three daughters, ages 13, 10, and 9.

(Grotto’s kids like these foods, but it may take a few tries to develop a taste for exotic fruits. Pomegranates are tart. Goji berries resemble stale raisins. And açaí can taste like cheese).

If you can’t stomach them, can’t find them, or don’t want to spend the extra money on them, don’t worry. Eating a wide variety of colorful fruits and vegetables is far more important than eating any one thing.

“Variety is the spice of life,” Grotto says. And, he adds, sampling exotic foods can be an adventure. So, make sure to enjoy the journey!

What Are Antioxidants?

Antioxidants are chemical compounds that may help fight the damage caused by diseases and aging. These powerful compounds work by blocking oxidation—natural chemical reactions that harm cells.

At the root of oxidation reactions are molecules called oxidants—often known as free radicals. These molecules are produced by nearly everything we do that involves oxygen, including digestion and breathing. Free radicals aren’t all bad. In fact, they perform important functions in the body, such as killing off old cells or germs. They become a problem only when we produce too many of them. Breathing in pollution or cigarette smoke often increases the production of free radicals. So does aging.

To prevent oxidation reactions from harming healthy cells, the body makes antioxidants. However, it tends to make fewer antioxidants as we get older. That’s one reason scientists suspect that oxidation is related to chronic disease. With fewer antioxidants to defend us, oxidation reactions can damage or kill more and more cells.

People aren’t the only ones who make antioxidants. Plants make hundreds of thousands of chemicals, also known as phytochemicals. Thousands of these phytochemicals work as antioxidants in the human body. Scientists now think that eating a wide variety of these compounds can boost our own antioxidant defenses, making us healthier and less likely to develop diseases.

That’s one reason why experts recommend that people eat many different kinds of fruits and vegetables.

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Going Deeper:

Additional Information

Word Find: Fruits Are Super

Six professional jazz pianists agreed to have their heads scanned by a team of researchers from Johns Hopkins Hospital in Baltimore and the National Institute on Deafness and Other Communication Disorders in Bethesda, Md. The musicians laid inside a large, tube-shaped machine called a functional magnetic resonance imaging (fMRI) device. The machine records blood flow. So when someone inside of it does or thinks about something, scientists can see which parts of the brain are working hardest.

This is a 1958 photo of the legendary jazz trumpeter Miles Davis. Jazz musicians improvise, which means they make up what they play as they go along. Every time they play the same song, it will include the same musical themes. However, every performance w

Wikipedia

Inside the fMRI device, the musicians propped a plastic piano keyboard on their laps. In one exercise, they played the notes of a scale in order. Then, they used the same notes to improvise a song.

In another exercise, the musicians memorized a jazz composition and then played it while lying in the fMRI device. As they played, they listened to a recording of other instruments playing the accompanying parts. Then, the musicians improvised while listening to the same background music.

Results from both exercises showed that the brain behaved in a particular way during improvisation. There was extra activity in a part of the brain that has been linked with the ability to tell a story about yourself. At the same time, there was less activity in the part of the brain that has been linked to planning and controlling behavior. Both parts are located near the front of the brain.

“What we think is happening is that when you’re telling your own musical story, you’re shutting down [brain cell] impulses that might impede the flow of novel ideas,” says Charles J. Limb, one of the researchers. He is a trained jazz saxophonist himself.

Improvisation is an important skill in creative pursuits. So next, the researchers plan to look for similar activity in the brains of poets, painters, and other artists.

Going Deeper:

Bower, Bruce. 2008. Riff riders: Brain scans tune in to jazz improvisers. Science News 173(March 8):148-149. Available at http://www.sciencenews.org/articles/20080308/fob4.asp .

Sohn, Emily. 2004. Project music. Science News for Kids (June 2). Available at http://www.sciencenewsforkids.org/articles/20040602/Feature1.asp .

DNA is genetic material that appears in every cell. Like your fingerprint, your DNA is unique to you—unless you have an identical twin. Scientists today routinely analyze DNA in blood, saliva, or hair left behind at the scene of a crime. The results often help detectives identify criminals and their victims.

Your cell phone can reveal more about you than you might think.

iStockphoto

Meghan J. McFadden, a molecular biologist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the device. This made her wonder whether traces of DNA lingered on cell phones—even when no blood was involved.

To find out, she and a colleague collected flip-style phones from 10 volunteers. They used swabs to collect invisible traces of the users from two parts of the phone: the outside, where the user holds it, and the speaker, which is placed at the user’s ear.

The scientists scrubbed the phones using a solution made mostly of alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got their phones back for another week. Then the researchers collected the phones and repeated the swabbing of each phone once more.

The scientists discovered DNA that belonged to the phone’s owner on each of the phones. Better samples were collected from the outside of each phone, but those swabs also picked up DNA that belonged to other people who had apparently also handled the phone.

Surprisingly, DNA showed up even in swabs that were taken immediately after the phones were scrubbed. That suggests that washing won’t remove all traces of evidence from a criminal’s device. So cell phones can now be added to the list of clues that can clinch a crime-scene investigation.—Emily Sohn

Going Deeper:

Perkins, Sid. 2008. Calling all clues …. Science News 173(March 8):158. Available at http://www.sciencenews.org/articles/20080308/note18.asp .

Sohn, Emily. 2004. Crime lab. Science News for Kids (Dec. 15). Available at http://www.sciencenewsforkids.org/articles/20041215/Feature1.asp .

Now, scientists have collected new clues about the canyon’s age.

New studies of mineral formations in caves along the Grand Canyon now indicate that parts of the chasm may be 17 million years old.

J. Powell

The canyon’s walls are full of caves that contain lumps of minerals called mammillaries. These mound-shaped lumps usually form just below the surface of pools that are full of minerals.

Water levels in such pools can drop when, for example, a change in climate occurs or the Earth’s crust shifts. The mammillaries remain, even when the water level drops. Scientists can analyze concentrations of metals inside the mounds to figure out when their pools went dry.

Carol Hill, a geologist at the University of New Mexico in Albuquerque, and colleagues studied mammillary formations in nine caves near the Grand Canyon. Most of these caves lie within a few miles of the Colorado River, which carved the rocky gorge. All the sampled mounds were within three-quarters of a mile (1.2 km) above the river’s current level.

Analyses of the mounds in the western region of the Grand Canyon suggest that 17 million years ago the level of groundwater in the area was about 3,800 feet (1,160 meters) higher than it is today. By 7.6 million years ago, the water had dropped to 3,050 feet above the river’s current level. About 2 million years ago, the water was only 390 feet (120 m) higher than it is today. Over that time, water levels dropped as the river carved deeper into the canyon’s floor.

In the eastern region of the Grand Canyon, analyses suggest that the river’s carving action started much later but took place far more quickly. In that area, the groundwater level (and probably the river level) dropped almost as far as it did on the western side, 3,000 feet (920 m), but in only one-fifth the time—just the past 3.7 million years.

Together, these data suggest that the Colorado River began carving the Grand Canyon at its western end. Later, the process appears to have continued upstream.

Going Deeper:

Perkins, Sid. 2008. Ancient chasm: Parts of Grand Canyon may be 17 million years old. Science News 173(March 8):147-148. Available at http://www.sciencenews.org/articles/20080308/fob2.asp .

Chances are, though, you’ve come face-to-face with plenty of these crusty, leafy, or shrubby growths. Lichens live on rocks, branches, houses, even metal street signs. You can find these often colorful organisms almost everywhere—from deserts to rainforests, Antarctica to Africa. They’ve survived trips to outer space, and some scientists suspect there might even be lichens on Mars.

“If you go into your backyard, you will definitely find a lichen somewhere,” says Imke Schmitt, a lichen researcher—called a lichenologist—at the University of Minnesota, Twin Cities.

What you probably don’t realize is that a lichen is more than a single thing. It is a thriving relationship between two different types of living organisms: a fungus and an alga. Neither of these organisms is a plant, so the lichen isn’t a plant either.

Different species of lichens can look very different from each other. Thorsten Lumbsch, a lichenologist at The Field Museum in Chicago, took photographs of two varieties of lichens—a rock lichen (above) and a spot lichen (below)—during a recent

Thorsten Lumbsch

Thorsten Lumbsch

Through photosynthesis, the alga harvests the sun’s energy to make food for the fungus, which provides a place for the alga to live. But the relationship is lopsided, Schmitt says, with algae caged like prisoners—even slaves—inside their fungal hosts.

Around the world, scientists have identified tens of thousands of types of lichens. At least as many probably still await discovery, says Thorsten Lumbsch, a lichenologist at the Field Museum in Chicago.

“Even in North America, there is a huge lack of knowledge” about lichen diversity and biology, Lumbsch says. “There’s a lot still to discover.”

As lichenologists continue to find new species of lichens, they are also working to understand how various species are related to one another. By putting together a lichen family tree, they hope to understand why so many different types of lichens have evolved in so many places around the world.

Most research involves attempts to understand basic facts about the organisms and their interrelationships. But researchers are also teaming up with lichens to monitor the health of the environment, among other applications.

Tough work

Studying lichens is rarely easy. Most species depend on very specific conditions, and scientists can rarely get them to grow in laboratories. This provides lichenologists a great excuse to travel around the world, scouting new specimens and insights.

Lumbsch, for one, makes several trips to Australia and South America each year. In the field, he searches for a group of crusty lichens that tends to be quite tiny—usually less than a few millimeters long. Finding samples takes patience and a trained eye.

“You have to look very closely,” Lumbsch says. “Usually, I know which species I’m interested in and which habitats they grow in. So, I go there and crawl on my knees on the forest floor with a hand lens.”

Like many lichenologists, Lumbsch (far right) travels all over the world to collect specimens. This photograph was taken on a research trip to India in January 2008.

Thorsten Lumbsch

Spotting lichens is challenging enough. Identifying them is even harder. Many species look exactly alike, even when they are only distant cousins. Closely related species, meanwhile, can live in totally different environments, or on opposite ends of the Earth. (One species, for example, is found only near both poles.)

When they’re done collecting samples, lichenologists bring their catch back to the lab. Under a microscope, the researchers classify samples by structure and color. Then, they grind specimens into a powder, from which they extract genetic material. These DNA molecules, which appear in all cells, make up genes, which determine how organisms look and work.

The more closely related two organisms are, the more similar their DNA will be. Comparing DNA from different species, then, can give scientists an idea of when each group split off from a common ancestor. Researchers use this information to build lichen family trees that depict kinship between species.

“Once we have these trees, we can ask a lot of interesting questions,” Schmitt says.

For example, family trees can help explain what the first lichens looked like, how they have evolved over time, and how far any given species has moved around the globe. Such insights should provide a window into our planet’s distant past. Some researchers think that lichens were the first organisms to live on land, long before plants evolved to do so.

“[Lichens] have an extremely long history,” Schmitt says. “This is what we are trying to uncover by building family trees.”

The work is slow going, she adds. “But we are beginning to see a picture emerging.”

Environmental police

Despite their reputation as scientific curiosities, lichens have a practical side. Throughout history, people have used different species to make dyes for fabrics, poisons for arrowheads, and “green”-smelling scents for perfumes. Birds use lichens to make nests. Reindeer and other animals, including some people, eat them. (Don’t try this at home—some species taste awful!)

In modern times, scientists have found a new role for these growths: as environmental watchdogs.

Although lichens can live in some of the harshest environments on Earth, Schmitt notes that they “are very sensitive to any kind of change that humans put on the environment.”

Some species of lichen are highly sensitive to changes in the environment.

Tsnena/Wikipedia

Studies show that some species quickly disappear when exposed to air pollution. These sensitive types also suffer from habitat loss due to logging, construction, or other environmental disturbances. The presence of lichens in an ecosystem, then, generally signals that the air is clear and the environment healthy. Their disappearance, on the other hand, can be a warning sign.

Lichens are good monitors of air quality. In fact, studies have shown higher rates of lung cancer in people who live in areas where sensitive lichens have died off. As a result, Lumbsch says, some European cities require developers to confirm the presence of sensitive lichens as a sign of habitable air quality before building new homes. Where lichens reside, city planners can feel confident that homeowners will have good air to breathe.

Among other projects, Lumbsch and his colleagues are looking at the effects of climate changes on lichen populations. Some day, he says, lichens might add service as global-warming sentinels to their list of accomplishments.

Lichens have long been overlooked. Chat with a lichenologist, though, and you’ll find plenty about these underappreciated growths to like, if not love!

Additional Information

Word Find: Lichens—What’s not to like?

Going Deeper:

Three thousand meters (9,800 feet) below the surface of the sea, the researchers observed what looked like an animal called Antarctic krill. Scientists had thought these shrimplike creatures lived only in the upper ocean, says Andrew Clarke of the British Antarctic Survey based in Cambridge, England.

This female krill, full of eggs, came from the surface of the Southern Ocean. Researchers have now glimpsed the same species at 3,000 m (9,800 feet) down.

British Antarctic Survey

Clarke made the discovery on a science cruise during the South Pole summer of 2006–2007 (a period which corresponds to the Northern Hemisphere’s winter). By that time of year, tiny floating organisms called plankton (a favorite food of krill) have multiplied in a big burst at the water’s surface. From there, they slowly drift downward.

Using a remotely operated vehicle that carried a video camera, Clarke and colleagues saw krill feeding on falling plankton. By studying the video footage, they identified the krill as the classic Antarctic species, Euphausia superba.

The species was fairly easy to identify. It is relatively large, for one thing, growing up to 6 centimeters (2.4 inches) long. It has distinctive red markings. And it feeds in an unusual way when it’s near the bottom. A krill nosedives into the sediment at the bottom, then scoops debris out of the water with spiny structures on its legs.

Based on the video evidence, “there isn’t really much else it could be” other than the Antarctic krill, says Stephen Nicol of the Australian Antarctica Division in Kingston, Tasmania.

Scientists have occasionally spotted this species of krill several hundred meters deep, but never in water as deep as this. So, the scientists are not exactly sure what’s going on. One possibility is that the krill simply stuck with their food as it sank ever deeper.

If big groups of krill do this often, scientists might have to revise their ideas about how many krill there are and how nutrients move through oceans.

“If the observation proves true about the krill at 3000 m,” writes Peter Wiebe of the Woods Hole Oceanographic Institution in Massachusetts (who’s currently on a different research expedition), “then it shows how little we really understand about how the ocean ecosystem is structured and functions.”

Going Deeper:

Milius, Susan. 2008. Hidden depths: Antarctic krill startle deep-ocean scientists. Science News 173(March 1):134. Available at http://www.sciencenews.org/articles/20080301/fob8.asp .

Schrope, Mark. 2007. Eyes on the depths. Science News for Kids (Dec. 12). Available at http://www.sciencenewsforkids.org/articles/20071212/Feature1.asp .Earth’s poles in peril. Science News for Kids (May 30). Available at http://www.sciencenewsforkids.org/articles/20070530/Feature1.asp .Coral gardens. Science News for Kids (March 1). Available at http://www.sciencenewsforkids.org/articles/20060301/Feature1.asp .

Sohn, Emily. 2007.

______. 2006.

______. 2004. Explorer of the extreme deep. Science News for Kids (Nov. 10). Available at http://www.sciencenewsforkids.org/articles/20041110/Feature1.asp .