Washington State University

Ask Dr. Universe

We eat well because bees have hairs!

January 6th, 2012

Dear Dr. Universe,
Why do bees have stuff that looks like hair? The hair on their legs looks like a real hassle, what with all the crud that sticks to it.
Elliott

Dozy autumn bee. By John Spooner/Flickr

Dozy autumn bee. By John Spooner/Flickr

That crud is their food, Elliott. That’s what I learned from Steve Sheppard. He studies bees here at WSU.

In fact, these hairs (which are branched, kind of like feathers) are one of the main characteristics of bees. They use the hairs to gather plant pollen. As they crawl in and out of flowers to gather the sweet nectar that flowers produce, the flower pollen gets caught on the hairs. The bees use their legs to comb the pollen down and pack it in little pollen baskets on their legs so they can carry more.

Bees are vegetarians. Of course, they make that nectar they gather from flowers into honey, which is their food supply for the winter. But even vegetarians need protein, and that’s what the pollen provides. They use the protein they get from eating pollen to produce “brood food” in special glands in their heads. You can think of flowers as a bee supermarket—a place where they can get all their groceries!

And this brings us to another question I got, from someone who didn’t include her name: “…I would like to know why bees are important to apples.”

Great question, says Professor Sheppard. Bees love apple blossoms. And that’s lucky for the apple trees—and lucky for us. This pollen that bees collect is the “sperm” of plant reproduction. Some plants can reproduce without outside help. (We’ll get to this in the next column.) But apples produce best if they get pollen from other apple trees.

Well, someone needs to move the pollen from a blossom on one tree to a blossom on another tree so the blossom can turn into an apple. That someone, more often than not, is the honey bee!

A single full-grown apple tree can have as many as 100,000 blossoms on it. Only a fraction of those will actually develop into apples. But still, it’s fortunate for the apple tree that they have the busy little bee.

One bee will visit 10 to 15 blossoms a minute and up to 5,000 a day! In order to produce one pound of honey, says Professor Sheppard, bees have to fly about 75,000 miles, about three times around the Earth!

But here’s the key point of all this. When the bee crawls in and out of the blossom, pollen from that blossom collects on the bee’s hairs—and one bee can carry around as many as 100,000 grains of pollen. And some of the pollen already on the bee from other blossoms gets rubbed off, so the blossom gets pollinated. The bee collects nectar and pollen, the blossom gets pollinated, we get apples and honey, and everybody wins!

And it’s not just apples. Professor Sheppard says that as far as what bees do, the pollination is actually more important to us than the honey–if you can imagine. About 15 percent of what we eat—both fruits and vegetables—depends completely on insect, mostly bee, pollination. Also, a lot of things we eat depend PARTLY on bee pollination. For example, the alfalfa that cows and other animals eat is pollinated by bees.

As important as honey bees are, they are not native to North America. They were actually brought here by European settlers. Even “wild” honey bees are bees that decided to go out on their own.

So before honey bees got here, who pollinated everything? Professor Sheppard says that before the settlers and their bees got here, all sorts of pollinating insects were doing the job, including thousands of species of “solitary bees,” bees that do not gather in hives.

But at least a couple of things have changed. Much of our farming today is in “monoculture,” huge fields in one crop. This does not provide a very good place for all these other pollinators to live. Also, even if they did hang around, huge areas of one tree or crop are just too much for these insects to handle by themselves. So be kind to those honey bees!

One more thing. Professor Sheppard is very interested in how honey bees evolved and where they came from originally. In a couple of weeks, he is going to Kazakstan. He believes there might be an undiscovered species of bee that lives there that would help answer some of these questions. I’ll keep you posted.

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Posted in Animals and Plants

Listening for worms

January 6th, 2012

Dear Dr. Universe,
We have a lot of robins that come in our yard to look for worms, which made me wonder: how do birds find worms underground?
Yours,
Charleen

Peter Cruickshank/Flickr

Peter Cruickshank/Flickr

Thank you, Charleen, for asking one of THE big questions that everyone wonders about. Of course, in spite of everyone’s wondering, this is another one of those questions whose answer no one is absolutely sure about.

I called ornithologist Richard Johnson here at WSU. He didn’t know the answer, but he dug out an article from 1965 in which a scientist from California named Frank Heppner reported the results of his worm-finding experiments with robins. After a series of experiments, Professor Heppner decided that robins find earthworms by sight.

That makes sense. Have you noticed how robins cock their heads from side to side? Their eyes are on the sides of their heads, so they have to turn their heads to see straight ahead.

However, says Professor Johnson, their EARS are also on the sides of their heads. You can’t see them, but they’re there, covered up by feathers.

So for 30 years, scientists tended to believe that robins find their food by sight.

Then we found an article that came out just last year, in a magazine called “Animal Behaviour.” Two Canadian scientists, Robert Montgomerie and Patrick Weatherhead, came up with a different conclusion.

They’d watched robins catch worms in fairly long grass, and it seemed to them that maybe they used another sense to find them. So they decided to do their own experiments.

For each experiment, they buried a bunch of mealworms in a tray of soil and let the robins go at it—but under different conditions. First, they buried two live mealworms and two that were frozen to death. The robins found the live ones, but not the dead ones. Since all the worms seemed to smell the same, the scientists concluded the robins probably don’t use their sense of smell to find them.

Another possibility was that robins sense worm vibrations in the soil. So the scientists rigged up the tray so the robins could not feel the vibrations through their feet. The robins had no problem finding worms. So vibrations are at least NOT NECESSARY for finding worms.

Next, the scientists buried the mealworms not quite an inch deep, laid a sheet of thin cardboard over the tray and put more soil on top of it. This would eliminate any visual cues, such as particles of soil moving around above the mealworm.

The result? No problem. They pecked right through the cardboard!

So where does this leave us? Besides taste, the only sense left is hearing. Do they HEAR the worms?

Professors Montgomerie and Weatherhead buried a little speaker in the soil with the worms and played “white noise” through it to block out any possible worm noise. White noise sounds like static on your radio.

Although the results were not completely clear-cut, the noise did cut down on the robins’ success rate. In fact, they didn’t even strike the ground as many times as they did in the other experiments.

So it seems that they DO hear the worms. Professors Montgomerie and Weatherhead figure the robins could hear some worms even through the white noise. Robins must have pretty sharp hearing!

By the way, what do worms moving in soil sound like? The scientists say that, when amplified, they sound like a person walking on gravel.

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Posted in Animals and Plants

Not (quite) by air alone

January 6th, 2012

Dear Dr. Universe,
How do plants get their food?
Catherine
San Diego, California

Sorghum, a C4 plant. Robert Hubner

Sorghum, a C4 plant that's very good at photosynthesis under adverse conditions. Robert Hubner (Read more about C4 plants in in Washington State Magazine)

How do plants get their food? Out of thin air, says Ernest Uribe, a plant physiologist here at Washington State University. A plant physiologist studies how plants work.

All living things, you realize, need energy. Animals get their energy and the materials they need to grow their bodies through the food they eat, which generally includes plants. Since plants have no mouths or digestive systems, how do they get their energy and nutrition?

Plants make themselves out of carbon dioxide from the air and water and a few minerals from the soil. They do this with the aid of sunlight, in a process called PHOTOSYNTHESIS, which means “putting together with light.”

This process was not always obvious to people. In fact, up until about 350 years ago, everybody basically agreed with Aristotle’s idea that plants just sucked their food up out of the soil as a pure “nutrient fluid.”

That’s really not a bad guess. After all, most plants do grow out of the ground. But think about it. Think about the trees in your yard. Every year the leaves fall, and you and your parents rake them up and haul them away. If that tree got its food from the soil, eventually it would suck itself a big hole, right?

This was what Jan Baptista van Helmont finally realized in the 17th century. In one of the first recorded experiments, he weighed a young willow tree, then grew it in a pot for five years. When he weighed it again, he found that it had gained 165 pounds. However, the soil in the pot had lost only a few ounces.

Van Helmont decided that it must be water that led to the tree’s weight gain and growth. Although he was wrong about the water, he was right about the tree’s food not coming from the soil—and he managed to completely change the way we think about plant nutrition.

What other scientists after van Helmont discovered is that plants use the energy of the sun to capture carbon dioxide from the air. Plants use carbon dioxide as a building block to make sugars and other carbohydrates.

How do they do this? Well, here’s where things start getting complicated, says Professor Uribe. And pretty neat.

Pigments in the leaves of plants absorb sunlight. The most important pigment is chlorophyll. Sunlight, as you might know, is actually different “wavelengths” of different colors of light. Chlorophyll absorbs blue and red light. The wavelengths of light that not absorbed are reflected—as green.

The energy absorbed from the sunlight dislodges electrons from the pigment molecules. The electrons then organize within the leaf cells into tiny electric currents. THIS is the energy that powers a series of very complicated chemical reactions. The first thing that happens is the plant splits water molecules into hydrogen and oxygen. Then it transfers hydrogen and electrons to carbon dioxide molecules.

This results in two things that are very important to us. First is the release of oxygen into the atmosphere. Second, sugar (glucose) forms from the combination of carbon dioxide, hydrogen and electrons. Here’s how chemists describe this sugar: C6H12O6. In other words, the glucose molecule is made up of 6 atoms of carbon, 12 atoms of hydrogen and 6 atoms of oxygen.

The glucose that the plant does not use immediately for food is used to make other kinds of storage carbohydrates and CELLULOSE fibers for plant structure.

However, even plants can’t live on air alone. Even though they do not suck nutrient fluid out of the soil, they do need some nutrients contained in soil. The main one is nitrogen. Nitrogen is necessary for making protein and nucleic acids. Nucleic acids are the main ingredient of DNA, the material that holds genetic information in every cell.

Plants also need phosphorus, potassium, sulfur, calcium, iron and magnesium, and a list of “micronutrients”: molybdenum, copper, zinc, manganese, boron, chlorine and nickel. And probably others in amounts too small for use to detect.

But mainly, plants get their food from the air, which is a lot more than the nothing it seems!

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Posted in Animals and Plants

Trouble in Bear Land

January 6th, 2012

Dear Dr. Universe,
How many grizzly bears are left in the world?
Anthony Alvarez
New York

Winnie the grizzly bear at WSU.

Winnie the grizzly bear at WSU.

As you can imagine, counting grizzly bears is pretty hard, and estimates vary a lot. Grizzlies might be big, but they don’t care to be seen. So I checked with Rob Wielgus, a wildlife biologist here at Washington State University who studies large predators.

He estimates that in the lower United States, there are probably fewer than 700-900 grizzlies. That, he says, is probably less than 1 percent of their population before the U.S. was settled by non-natives. There were about 100,000 bears in the lower U.S. in the 1850s, but they have disappeared from 99% of their former range. Professor Wielgus adds that there are probably 700-800 grizzlies in Alberta. British Columbia might have as many as 10,000-13,000, though he says that is a government figure and could be way too high.

There MIGHT be 35,000 grizzlies in Alaska and 6,500 in the Yukon, but Professor Wielgus says these guesstimates could be way off.

But you asked about the world population. Grizzlies, also called “brown bears,” live in Asia and Europe. In fact, most of the world’s brown bears live in the conifer forests of the former Soviet Union. The total worldwide population? Perhaps 125,000-150,000, but no one really knows. Most biologists believe that grizzlies are declining worldwide.

So even 150,000 isn’t very many if present trends continue.

In spite of grizzlies being “threatened” in the lower U.S. and “vulnerable” in Canada, they are still hunted, which causes some unexpected problems, says Professor Wielgus.

One common justification for hunting grizzlies is that killing large males makes more room and more food for more cubs. According to this argument, “removing” adult males increases the number of cubs produced by females and cub survival rate. More available food means more cubs.

Professor Wielgus believes the opposite happens.

Grizzly cubs stay with their mother for as many as three to four years. The number of female grizzlies in an area depends on how much food there is. The number of male grizzlies depends on how many female grizzlies there are. If the food is plentiful, a grizzly male’s home range will be about a thousand square kilometers.

A male grizzly does not appreciate male company. He wants these females for himself, to raise HIS cubs. So if another male tries to invade his turf, he’ll kill him or chase him off.

But let’s say some trophy hunter wants a bear rug for his den, so he shoots Mr. Griz. What happens next, says Professor Wielgus, is that all these younger male grizzlies come to the funeral and start fighting for the territory.

Even if one of them chases off his competitors, that’s not good enough. HE wants the females to himself, to start producing HIS offspring. But if females are nursing cubs, they cannot get pregnant.

This is a major problem to a young male who wants his own cubs. So he starts killing the cubs to make room for his own and to get the female to breed. Grizzlies can be pretty intense.

Of course the female grizzly is not going to hang around and have her cubs killed. She might take them out of the area, maybe to where there’s less bear food and solitude, where males are unlikely to go. Maybe, in other words, to real crummy areas where food is scarce. Or she moves into human territory and starts digging through garbage cans.

So let’s sum up. What happens when somebody shoots a large male? The grizzly world gets very upset. Lots of young males, who are often troublemakers, move into the territory. Mrs. Griz might go to town to escape the new guys.

Also, more males means more demand for food. Of course, humans get all upset when the young males start showing up in their back yards and eating their sheep. So somebody decides, hey, we’ll solve this problem. We’ll shoot that male and everything will be fine.

WRONG, says Professor Wielgus. It just starts the problem all over again! The griz population gets bigger because of more young males! And more ornery.

But what happens eventually, says Professor Wielgus, is the population just can’t stand the upset. Because of the influx of males, the population goes up, up, up. Then all of a sudden, all of the offspring have been killed, there are no more females, and without females, it’s good-bye grizzlies.

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Posted in Animals and Plants

Yes, you are what you eat. Kind of.

January 6th, 2012

Dear Dr. Universe,
Why do people like different foods?
Nicole Ruslim
Melbourne, Australia

Fudge from Seattle's Fat Cat Fudge. by Matt Hagen

Fudge from Seattle's Fat Cat Fudge. by Matt Hagen

This is one of those very complicated questions that require a lot of experimentation. So let’s do some research on whether you and I like the same foods or not!

Seriously, lots of scientists are also interested in this question. Bob and Sue Ritter here at Washington State University have studied forms of this question for much of their careers. Sue Ritter studies appetite, or what makes us start eating. Bob Ritter studies satiation, or what makes us stop eating.

When I went to visit with the Professors Ritter, I just happened to have a bag of pretzels with me. Professor (Sue) Ritter admitted that they looked pretty good to her. It was late afternoon, and she hadn’t eaten since breakfast. Her blood glucose—a sugar that the body uses to store energy and then release it when needed—was getting pretty low. Pretzels are high in carbohydrates, which change to glucose during digestion.

Professor Ritter was also hungry for salt, which our bodies need. The sodium and chloride in salt, along with potassium, are ELECTROLYTES. Electrolytes help the kidneys manage the body’s fluid levels. Salt is also necessary for the “action potentials” that make your brain and nervous system work.

In general, when you get hungry, your body is signaling you that you need some energy. Your body has different “receptors” in the brain and other organs that tell you, I’M HUNGRY whenever they need energy. These receptors also look for specific nutrients. When they figure you’ve had enough, they send signals to the brain to shut off the energy alert.

The brain in particular says “AND I NEED IT RIGHT NOW!” Think about it. Your brain is running your whole show, which takes a LOT of energy. Even when the rest of the body is satisfied, the brain might need more energy. In fact, says Professor (Sue) Ritter, we may overeat sometimes because our brains still need energy.

And how exactly does the brain get this energy? From glucose. Glucose is the only energy source that can pass through your blood-brain barrier, which is a filter that keeps toxins away from your brain.

This does not mean, however, that every time your brain feels a little tired, you should wolf down three candy bars. There are plenty of better ways to get glucose. Fruit is a good one. Also, the brain can store only a little bit of reserve energy. If your brain doesn’t need the extra energy at the moment, and neither does the rest of your body, where’s that extra “energy” going to go? FAT!

So, to some extent, your taste for different foods is your body’s way of telling you what it needs. Maybe on Tuesday, your body feels a little low on Vitamin A. So you eat something with a taste that your body knows has provided Vitamin A in the past—carrots, maybe. Or you need some protein. So you munch a bag of nuts. That’s okay.

But just because you want salty, fatty chips doesn’t mean your body NEEDS fat. In other words, just because you’re hungry for fat doesn’t always mean you need it.

In fact, Professor (Bob) Ritter and his colleague Mihai Covasa believe that a lot of us have become IMMUNE or insensitive to fat. Their experiments suggest that if all you eat is chips and fast food, which tend to be very high in fat, eventually your body’s “I’m full” signals quit working properly.

And eventually you become what you eat. You become … fat.

I also visited Mary Watrous in the history department here at WSU. She studies the role of food in different cultures and how women carry on food traditions. She says that people like specific foods because that’s what everyone else in their culture eats. Seems obvious, right? But think about it. Food can have different meanings. Maybe you like a certain food because your grandma makes it for you, and she likes it because her grandma made it for her. Or you might like a food, and dislike others, because it has special meaning in your religion.

People also differ in HOW they taste certain foods. Some people have genes that make them SUPERTASTERS. Supertasters taste certain bitter compounds in foods (such as in Brussels sprouts) that other people don’t notice.

Also, your taste may change as you grow up. Is there something that your mom loves, but you hate? She probably thinks that you’re just being persnickety. “Just try it, you’ll like it,” right?

But according to Adam Drewnowski, who studies nutrition at the University of Washington, maybe it really DOES taste awful to you. Explain very politely to your mother that you’ve been doing some research, and that you’ve learned that maybe your taste buds haven’t matured like hers. You might even compromise and suggest that even though the broccoli tastes bitter to you, it might not taste so bad if she put a little cheese sauce on it.

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Posted in Human Body and Behavior

More than just a pretty bug!

January 6th, 2012

Dear Dr. Universe,
What are butterflies good for?
David Steury
Potlatch, Idaho

Fender’s blue butterflies

Fender’s blue butterflies. Read more in Washington State Magazine.

It just so happens that Robert Michael Pyle was here at Washington State University the other week to talk about butterflies. Mr. Pyle is a lepidopterist, which means he studies butterflies. He is the author of many books about nature and butterflies, including The Audubon Society Field Guide to North American Butterflies. He recently wrote a book called Chasing Monarchs, about following Monarch butterflies on their migration from British Columbia to the Mexican border!

So what are butterflies GOOD for? Humans tend to think of things as either good or bad (for humans!), and the same goes for insects. Insects are either pests or “beneficial,” which basically means “good to humans.” Well, that’s only part of the story, says Mr. Pyle.

Most insects are neither “good” nor “bad.” They’ve probably never seen a human and could care less about people. But they all perform some role in nature.

And this certainly includes butterflies.

A big job that butterflies do is pollinate plants so that plants can produce seeds and fruit. Many plants need help getting pollen from the flower’s male stamen to the ovules, either from their own flowers or from other plants of the same species. Ovules are like plant eggs, from which the seeds grow.

Many insects—including wasps, beetles, bees and flies—pollinate plants when they search for flower nectar for food. The pollen from one flower sticks to the head or legs of the insect and then falls off in another flower.

Butterflies are great pollinators, says Mr. Pyle. Their proboscis, a long feeding tube, reaches way down into the flower to suck nectar, and their heads get pollen all over them.

Butterflies are also food to many birds. They are particularly tasty when they are still caterpillars. Moth and butterfly larvae are a major food group for warblers and many other songbirds.

Butterflies, like other insects, can change plants through adaptation or evolution. Butterflies, particularly their larvae (the caterpillars), and other insects eat plants. These plants don’t always just stand there and take it. They develop defenses. One way is to produce substances that are either poisonous or taste bad to the insect.

However, many of these substances actually taste good to humans! Plants that have developed defenses against insects (and resulting good tastes to humans) include onions, cilantro, basil, cabbage and peppers.

Butterflies also let us know how the rest of nature is doing where they live. If their home is healthy, then they are usually healthy also. If their home is not healthy, then neither are they. Other animals besides butterflies are also thought of as “indicator species.” But the nice thing about butterflies, says Mr. Pyle, is that they are so visible.

If a place has a lot of butterflies, which then become fewer or disappear altogether, then that’s a pretty good sign that place has problems. Maybe too many chemicals are being used to kill other insects. Or maybe too many humans have moved in and destroyed the butterfly’s habitat. If that’s the case, the habitat has also disappeared for a lot of other animals and plants.

And when this happens, we have lost something very special. Mr. Pyle says butterflies are especially GOOD for their beauty. Imagine, he says, a world without butterflies. “I think the world would be a much poorer and sadder place without the brilliance and excitement and sheer pleasure that the sight of a butterfly brings.” I agree.

Thanks for a great question!

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Posted in Animals and Plants

What do bears eat?

September 22nd, 2011

 

[+] Click the comic below to view full-size.

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Posted in Animals and Plants, Biology