For the love of Chocolate

Continuing with the Halloween theme, today I write about candy. And, not just any candy - chocolate. Almost everyone likes chocolate, and some of us love it. I know I am certainly guilty of raiding my kids’ trick or treat bags in search of the good stuff; which in my book is the solid chocolate without anything else getting in the way. No peanuts, no nuts, no crispies, no crunchies, no wafers, and not even caramel. Just chocolate.

What is it about chocolate that makes so many of us crave it. Turns out there is some solid science behind this apparent madness.

First of all, there is the chemistry. Scientists have discovered several properties of chocolate that literally lead us to crave it. One, it has opioids. Opioids are also found in opium. So, not surprisingly, chocolate, like opium, serves to dull pain and give a general feeling of calm and happiness. Of course, it is present in pretty small doses, so chocolate is a lot safer way to get these feelings! Two, chocolate has caffeine, which is an upper, which tends to make your heart beat just a little faster.

Second – the psychology. Because we tend to give gifts of chocolate to people we love, some theorize that eating chocolate can induce feelings of comfort and/or love for purely psychological reasons. Given the chemistry above, and the biological responses, it is no wonder people have associated chocolate with love. But our resulting cultural association of chocolate with love has trained our emotional responses as well. Even without the underlying chemistry, giving, receiving, or just eating chocolate tends to induce happiness.

Third – the biology. Chocolate really is good for you, at least in moderation. Chocolate contains antioxidants, and flavenoids, both of which are thought to increase your life span through their cardiovascular benefits. In simpler terms, chocolate is good for your heart, biologically-speaking. And, we know that our bodies tend to crave the things that are good for us. It is our bodies’ way of telling us we are short on particular nutrients.

Of course, we also routinely crave what is not so good for us, and too much chocolate definitely falls into that category as well. Chocolate has lots of fats, and sugars. The fact that it contains all those fats, which make it smooth, may also explain some of why we like it so much - the sensation of eating it.

So whatever the reason, enjoy!

Spooky Spiders…

October seems the appropriate month to continue on the theme of spiders and other creepy crawlies who happily decorate our homes right now in larger-than-life form. Last time I wrote about spider silk, and its amazing strength. Spiders are biological wonders from several other perspectives as well. Notably, their long and leggy legs.

First, have you ever noticed that when you find a dead spider, that its legs are all curled up (so long as it is not smashed, that is)? Their legs roll inward towards their bodies and form a sort of ball. This is because spider legs are hydraulic, like pistons. They are held rigid by the fluid inside them, and that fluid must be maintained at pressure in order for them to hold the spider up and allow it to move around. Once the spider dies, the pressure cannot be maintained, and the legs collapse.

To move, the spider has muscles within the legs that allow the seven (yes seven) sections of each leg to bend inward a coordinated manner. But, to straighten the leg, there are no opposing muscles in most spiders, because there is nothing to attach them too. Remember spiders have no bone, just their tough exoskeleton that makes up what we think of as their crunchy skin or shell. The fluid pressure in the leg is changed via changes in the spider’s blood pressure. Increases in pressure straighten the leg, decreases allow it to bend.

Jumping spiders are by far the best at this feat. They can quickly change the blood pressure in the legs which allows them to spring upwards, travelling as far as 25 times their body length. That’d be 25 to 30 feet for the average human. None of us can pull that off.

Running spiders are special again in their own way. They have given up web building entirely for the purposes of capturing food, and obtain their meals hunting them down and then overtaking them with sheer speed. Our common wolf spiders often hunt this way. Luckily, even the largest of wolf spiders is only about an inch long, because spiders running you down is enough to unnerve just about anyone. They play an important role in the control of other insects, however, so be thankful that they are there.

Fishing spiders, however, win the award for amazing legs. Fishing spiders can literally walk on water. They do this by abusing the laws of physics, and taking advantage of simple surface tension. Surface tension is the tendency of particles of water to stick together. This is why you see a drop of water form a round, bead-like drop, and not just scatter into its infinitesimally small molecules. Fishing spiders have tiny leg tips, and light bodies, and when they press these leg tips to the surface of the water, they are able to stay atop the surface, and not break the surface tension. This is due largely to a waxy coating on the legs. You see a small dimple form on the water from the pressure of the leg, but the tension does not break, unless the spider wants it to. These spiders can dash out onto the water to grab prey such as insects, or reach below the surface to grab even small fish. And, when they really need to move, they can rise up on two legs and gallop across the water, reaching speeds of about 30 feet per second, or 2 miles per hour. The average running speed for a person is 6 miles per hour. The world record 100 m dash clocked in at 28 miles per hour. But, when they are just hanging around, or casually need to move from place to place, fishing spiders can also place their legs on the water and sail with the wind.

Not a bad way to get around.

Stronger than steel...

The strength of nature can be an impressive thing. Biologists, physicists, engineers and chemists alike often spend a lot of time just trying to figure out what makes things as strong as they are. What makes the shell of a clam rigid and tough? What makes the silk of a spider pliable yet strong?

This is an area of research called biomaterials. The study of biological substances and their physical properties in terms of measurements like strength and stiffness.

Recent research by scientists at the University of Puerto Rico has revealed that the toughest material on the planet is spider silk. In particular, the trophy goes to the web-spinning silk of the Darwin's bark spider, which lives on the island of Madagascar. This spider spins enormous webs that extend across rivers. Therefore, they must stretch and contract as the trees (to which they're anchored) move in the wind.

Spider silk, in general, is amazing stuff. It is a protein. It is both strong, meaning it resists breaking, and it is elastic, meaning it can deform and then recover its shape. Many materials have to trade off these properties. A substance can be very strong, like steel. But, steel is not elastic. If you bend steel, it will not return to its original shape. Spider silk, on average, has the same tensile strength as steel. But at the same time, it is very ductile, and can stretch about one and a half times its own length before breaking.

The bark spider of Madagascar spins fibers that are stronger than the strongest known man-made substance, which is Kevlar. Kevlar can resist about twice the force of steel. This is why they make bullet-proof vests from the stuff.

Spiders also can change the properties of their silk, by changing the water content of the silk. Most spiders can also weave more than one kind of silk, generally speaking there is strong silk that creates the support for the web, and sticky silk that catches the prey in the web. When you put these two abilities together, you end up with about a dozen distinctly recognizable kinds silk that can be produced by just one spider depending on the job at hand. The silk used to wrap up prey is even stronger than the silk used to support the web, and the silk used to form egg sacs is stronger still. Therefore, both of these silks are stronger, on average, than steel. At the other end of the spectrum, many spiders, particularly those that have just hatched, can extrude long, very thin strands of gossamer silk used for ballooning to new locations to settle and build their own webs.

The impressive properties of spider silk make it popular for study by engineers hoping to mimic Mother Nature. Unfortunately, it is not possible to create spider ranches so that the spiders can do the work for us. Spiders are not like docile cattle, making them extremely poor candidates for domestication. Spiders are aggressive and will eat one another, making it inadvisable to keep many spiders together in the same space. Reproducing the properties of the silk with man-made mimics is the only viable option, though scientists have created transgenic goats that will produce spider silk (I’ll save the ethical debate about that sort of process for a later article!).

For right now, the score is still Mother Nature 1, Humans 0 in terms of who can make the stronger substance.

Getting a Kick out of Physics

I’ve written before about the physics of baseball, and in particular how curve balls curve. But, this year’s World Cup Futbol (that’s Eurospeak for soccer you know) got me thinking about the physics of soccer and scoring goals. And, since it is that season for some of you parents, youth soccer season, that is, here you go…

The famous goal that recently got headlines again, in terms of the underlying science, was actually scored 13 years ago. In the June 3, 1997, match between France and Brazil. In the last seconds of the game, Brazilian Roberto Carlos scored what was later named the impossible goal. He kicked a ball towards one end of the goal, apparently way off target, that banked at the last second and dropped into the net. It tied the game and changed the team’s fate that year. It has the stuff of the mysterious dropping fastball in baseball.

The secret was finally revealed this year by a team of French (of course) scientists.

Soccer balls tend to curve or arc when kicked for much the same reason that curve balls curve in baseball. When they are kicked (or thrown) they tend to rotate. So, one side of the ball is rotating in the same direction as the ball itself, while the other side of the ball is rotating against the direction of motion. The side of the ball that is rotating against direction of motion gets slowed down, just a little, by the resulting friction, and the path of the ball starts to curve to that side. This is called the Magnus effect, which explains the gently curving motion we typically see in tennis balls, golf balls, etc. What about the radical change in direction, like with old-fashioned spit-balls and this famous soccer goal?

Spit-balls change drastically because the shape of the ball is altered. This causes the spin to be asymmetrical, and things start to wobble. Just think of your washing machine on the spin cycle with the load out of balance. It just takes one wobble to throw things really out of whack. If your washing machine drum were not attached to the machine, it would take one strong turn, and crash through your laundry room wall.

Something quite different apparently happened with this soccer ball. No alteration of the ball was required. It was simply that the ball was kicked from so far away that the Magnus effect went into overdrive, so to speak. The forces on the right and left side of the ball got so out of balance that it started to wobble on its own, and the result was just like a dropping curve-ball.

The key was that the kick was from really far away, 35 meters to be exact, and only a player like Roberto Carlos could deliver that kick with enough speed for it to actually make it to the goal, estimated at 130 kilometers per hour. Hence, you almost never see this happen. You never see it in baseball or tennis, the ball does simply not get to travel far enough. And, it is obviously incredibly rare even in soccer, kickers rarely deliver 100+ km/hr kicks.

In fact, scientists did not know this was the outcome of the Magnus effect until seeing that goal, and spending many years since then studying it. It has now been replicated in the lab. We have yet to see if improvements in player training technology will yield more Carlos-style performances.

The cost of going organic

A recent study publicized at Arizona State University really hit home the pros and cons of the organic food movement.

This research revealed that most stores, grocery stores at least, now carry some form of organic foods for their customers. The number of organic offerings has been steadily increasing, and prices are slowly, ever so slowly, coming down.

Why are the prices so high? I had always assumed that it was because of a reduction in the amount of product on the market. I am drawing here on my old Econ 101 course, which is rusty, at best. But, supply and demand theory dictates that if there is less supply, demand will go up, and prices will increase. I like that Economics works just about like Ecology, just with money instead of animals. Competition is competition. When resources are scarce, they become more valuable, competition becomes more intense. In fact, the mathematical concepts we teach students about population growth were developed by a banker interested in the nature of compounding interest on investments. But, I digress…

Demand. Without fertilizers, the crops might yield less. Without pesticides, the crops might yield less. Less product, more demand. Demand is there in the first place because of public perception. People perceive that eating organic is better for them, and better for the environment. However, in this case, demand is out-pacing supply, and driving prices way up (think of gasoline as another example; people will typically pay whatever the price is at the pump, and frequently that price has nothing to do with the current price of a barrel of crude, and everything to do with the location of the gas station and if it is summer and people are going on driving vacations).

Now, it IS more expensive to produce organic products, produce in particular was the focus of this research. Taking a traditional farm and re-fitting it, and its day-to-day practices, to organic standards is not easy, or cheap. So, naturally, the wholesale price of produce is higher. But, these researchers found that the profit margin did not come from the markup from wholesale to retail. Grocers typically make around a 75% profit on conventionally grown produce. They make only a 7% profit on organic produce. Yet, the grocers still sell the products because of the demand.

This realization that the profit may lie in the hands of the producers is enticing more people to grow organic, despite the costs. This is actually a good thing, that the growers/suppliers should actually possess the market power. And, as this happens, and more product hits the market, good ol’ Econ 101 predicts that prices should fall. This means such produce will be more readily accessible.

The real cost to you and I may come in the form of the foreign markets. Already, there have been suits brought against bargain grocery chains that claim to sell organic, when the product was not. The foreign growers are anxious to get in on a market where the power favors the growers. Indeed, cruising through most local stores these days reveals that much of the organic foods are not local, or American, in origin. There is a great debate among food purists about getting local, versus getting organic. The benefit of choosing local sources is that it keep your money local. The risk of foreign sources is that the foods may not be grown to the same standards.

The old adage, you get what you pay for, still applies here, and if it seems to be too good to be true, it probably is.

What in the World?

Or not.

We, the inhabitants of this world we call Earth, have tended to think of our little planet as being rather special. It is the only one, or at least the only one that we know of, that harbors life.

This is particularly special for me as a Biologist. Biology is the study of life. As such, I would be unemployable on any other planet. And, well, also likely dead. But, I digress…

At a recent conference, a scientist who is part of NASA’s Kepler scientific team announced they had discovered many earth-like bodies in outer space. In fact, of the planets now discovered, planets that are earth-like dominate in terms of number. There are more earth-like planets than any other planets.

What might it mean? Well, so far, no one knows. The earth-like planets are simply those that are nearly the same size as earth. That is the point of the Kepler satellite mission. To map the galaxies, using size as first cut for determining which planets might be like our own little rocky planet, and might be habitable, or even inhabited. The Kepler satellite is looking specifically for earth-sized planets orbiting a star, just as we orbit our sun.

But, finding earth-sized planets, in and of itself, is a pretty amazing finding. These apparently litter the Milky Way. And, until now, most of the new planets that have been discovered are more like the gas giants, like Jupiter and Neptune.

The fact that we are a little rocky planet, by comparison, is actually pretty important, and pretty fundamental in the maintenance of life. Our planet has a surface that we can live on. We are the only planet with liquid water. And, we have an atmosphere that facilitates temperature and moisture regimes that we can tolerate. These things are not possible on large, gassy planets. So, it helps that these potential planets are earth-like in size.

However, we do not yet know if they are rocky. Nor do we know if they are orbiting too close to, or too far from, their suns to maintain suitable temperatures. We do not know if they have water, or any sort of atmosphere.

But, at least there is exciting new potential. Kepler scientists recently revealed that there might be more than 700 earth-like planets out there orbiting another star.

Dracula Minnow

Recently I wrote about the vampire squid, and I argued that I really didn’t have to look any further for a more flashy, eye-grabbing title. I stand corrected. A group of scientists recently discovered a new minnow, and it has got a pair of choppers projecting from its jaws that earned it the name ‘dracula’. International Institute for Species Exploration at Arizona State University recently named it one of the top 10 new species of 2010.

Measuring just 17 millimeters long when fully grown, this little minnow, while tiny, is a close relative of the common goldfish, the carp, and the other minnows you might have known from childhood. Many of your pet store variety fishes are in this group of carps and carp-like fishes. And, if you have looked closely at Goldy residing in your child’s fish bowl, you might have noticed Goldy has no teeth. This group of fishes has been around for a long time, and, in fact, lost anything even resembling true teeth nearly 50 million years ago. But, the dracula minnow has developed bony spurs on its jaws that project through the skin and look just like nasty fangs.

Just the male has these fangs. Why? It is completely unknown. This little fish is completely transparent. And, it is so small because its development was apparently truncated somehow. So, the adults look like they are still larval fishes. They possess at least forty fewer bones than other closely related adult fishes.

Other species on this list include an amazing carnivorous (yep, meat-eating) sponge, and bug-eating slug, an electric fish, a psychedelic frogfish, a tiny new mushroom with the scientific name Phallus (I’ll let you Google it to see why it earned this name, though you probably don’t have to think too hard to figure it out), a new species of yam from Madagascar, a giant orb-weaving spider in which the female is four times larger than the male (they managed to figure out the male and female were of the same species), a deep-sea worm that shoots glowing green blobs of goo at its predators, and a giant carnivorous pitcher-plant the size of a football.