thnks for your help!

A: Good question! Water is so important to us that it makes sense (no pun intended) that our ancestors should have been able to "smell it out". Other mammals seem to be able to find water by scent. Let’s look at what makes something detectable by smell.

1. Molecules of the substance have to get into the air, and then into our noses. Some things get into the air easily, like gas fumes, other things don’t.
2. Molecules have to get a reaction from the nerve endings in our nose. Some molecule shapes get a big reaction ( like the ones in perfume or skunk spray), other molecules don’t.
3. Our brains have to de-code the message from our noses.

Well, we know water molecules do get into the air, that’s what happens with evaporation. Water molecules have a very simple shape; just 2 hydrogens and an oxygen. Perhaps they just don’t get a big reaction from the sensors in our nose. The last step is important too. Compared to other mammals, our brains are not very good at recognizing odors. Dogs have 14-20 times more "smell receptors" than we do. They also use a lot more of their brains to process the information, so their sense of smell is about 100 times better than ours. Wolves can smell prey animals up to 1.5 miles away if the wind is blowing the right way. That’s nothing compared to the male silk moth. He can smell one molecule of a female’s scent in 1,000,000,000,000,000 molecules of air!

So why can’t we smell fresh water? Part of the reason may be that water is not getting much of a reaction from our "smell sensors" due to its molecular shape. Another reason is that our odor gathering and processing system is not as good as that of other animals. Our ancestors may have used logic, memory, communication, and visual cues to help them find water. They also may have paid more attention to smells than we do. You can probably recognize your favorite songs quickly, but all of the music you don’t enjoy may sound pretty much the same. If we had spent our lives paying more attention to smells, especially important ones like water, maybe we could smell it better. Of course, we’d still never be as good as it as dogs are.

Good information about the sense of smell is available at:
http://weber.u.washington.edu/~chudler/nosek.html

Thanks for asking,

Becky

Thank you for your help.

A: That's a good observation. When you see blood outside the body it is usually a dark red. This blood is from the veins. Sometimes you may cut an artery. This blood is bright red. It also spurts out in pulses instead of oozing like the blood from veins. So even outside the body, blood can be different colors. (What's the difference between veins and arteries and why would that affect the color? Why does areterial blood spurt?) The blood vessels you see at the surface of your skin are veins. Everyone's skin is slightly different in color, so the veins can look different in different people, but blood is exactly the same color in everyone. It still doesn't look red. That's because we're seeing the *walls* of the veins too. When you see lemon-lime flavored soft drinks in plastic bottles they usually look green, but when you pour them out, they're often clear or yellow. It's not the blood that's bluish, it's the whole vein, including the walls, just like the soft drinks look green because they're in colored bottles.

Have you ever seen a totally white rabbit or mouse? They're called "albinos" because they can't make pigments (the substances that color our eyes, skin, and hair). Their veins look red, even though their blood is the same color as ours. Why is that?

If your school has access to the world-wide web, you can find out more about veins and arteries at: http://sln2.fi.edu/biosci/vessels/vessels.html

Thanks for asking,

Becky

A: You made a great connection between what you saw in water and what happens in blood. You probably know that blood is mostly water, so it makes sense that the pH would go down in the watery part of blood. Blood also has special molecules inside red blood cells called "hemoglobin". Hemoglobin is very good at carrying oxygen and carbon dioxide. This means that even more carbon dioxide can "fit" into blood than can "fit" into water, so the pH can change even more. In fact, low pH is one way your body senses it has too much carbon dioxide and not enough oxygen.

Carbon monoxide is found in car exhaust and smoke. It sticks to hemoglobin 200 times tighter than oxygen does. Why is it unhealthy to be around too much car exhaust?

I see that you have access to a computer. You can learn more about blood at http://sln2.fi.edu/biosci/blood/blood.html

Thanks for asking,
Becky

A: I have always been interested in animals, particularly mammals. I also have a very curious nature-I always want to know "why".

A: We could probably build a self-contained area on the moon and live in it temporarily, but the cost would be enormous. You can estimate it if you find out how much it costs to send a kilogram of something to the moon.

How many people would be living there? How big would the space need to be? How much would the building weigh? Now you have to transport that to the moon, plus all the tools and materials, workers, and the space vehicle itself. Remember that the workers have to live in the ship while the moon base is being constructed. Construction would be very slow because workers would be in clumsy suits. Robots might be used for some of the work. We would have to transport them too. How long would the people be living on the moon? Every day a person uses 500 l (125 gal) of water here on earth. (That doesn't count the 7200 l used per person per day for farming, manufacturing, etc.) How much would the water supply weigh? Now for the oxygen. How much of that do you need per day? Then there's food, fuel, batteries, medical supplies, etc. You can probably think of lots of other things that you will need.

You couldn't stay on the moon for too long. When our bodies are weightless, they start breaking down. One problem is that our muscles atrophy (get weaker).

The bottom line is that it would be an adventure to visit there, but you couldn't stay there long. The people on Earth would have to work extremely hard to get you and your stuff there. It's another good reason to take good care of the Earth.

A: Okay, this is going to be a long answer. You might want to read a paragraph at a time, think about it, and think about how you would interpret the evidence scientifically. Remember that science can only test things that obey natural laws. People all over the world have different stories about where we came from. Almost all of these stories contain some supernatural force such as one or more gods or spirits. Science can not be used to test whether any of these stories is right, or even which supernatural story is the best. Any explanation that is scientific has to explain what we see without using any supernatural explanations. This doesn't mean anyone else's story is wrong, it just isn't science.

Scientists know we didn't actually evolve from modern monkeys, but the evidence we have suggests that we have the same ancestor that they do. There are several lines of evidence that lead scientists to believe that all forms of life evolved from only one or a few forms that first existed about 4 billion years ago. One line of evidence is fossils. (What is a fossil?) In the deeper layers of the Earth's crust we find no fossils. Then we find fossils of simple organisms in younger layers. As we go up higher in the rocks, we start finding larger, more complex organisms along with the simple ones. Sometimes we see fossils that look like a step between older fossils and newer ones. As we travel through time (up the layers of rock), we also see some kinds of fossils disappear. These types of plants and animals probably went extinct. The first primates appeared in the fossil record about 70 million years ago. (What is a primate?) In rocks that are about 3 million years old, the first human-like fossil skeletons were found. They aren't exactly like ours. They are smaller, and their brains would have been rather small compared to ours. They had large canine teeth. In even younger rocks, there are skulls that are larger and had bigger brains. Some of these lines went extinct. The first skeletons that look like us appear in rocks that are about 200,000 years old.

A second line of evidence comes from looking at the bodies of modern animals. If we look at any primate, we will find exactly the same bones, even in primates that spend all of their time in the trees. We have many other similarities, some you can see on the outside, some are internal, and some are biochemical. We can use a variety of tests to see them. For example, if you compare DNA (what is DNA?), you will find that about 98% of our DNA code is just like that of chimpanzees. The other 2% is what makes us different from them.

Anther kind of evidence is developmental. If we study vertebrates (things with backbones and skulls) as they change before birth (or hatching) we see that at the earliest stage, all look the same. Months before we were born, all of us had gill slits and tails. These things disappeared as we developed inside our mothers. This suggests that our ancestors had a use for these things, even though we don't need them now. Our development is not an exact record of our evolution, but it can give us clues.

Another bit of evidence is found in "useless" structures on living adult animals. For example, some species of snakes and whales have pelvic and leg bones even though they do not now have legs that are visible. These bones do not 'do' anything, so it seems likely that they're 'leftovers' from ancestors that had legs. Our own small fang-like canines don't have any obvious use, but could be a leftover from the early primates. Another such structure is the appendix, which is a "dead end" off your large intestine. In many animals this is a large structure that is used to help digest plants (the cecum). In us it is not only useless, it is dangerous. Many people die from appendicitis.

That is a brief look at the facts that led scientists to come up with an evolutionary explanation for where we came from. While there are many stories of human origin that include supernatural forces, this is currently the only scientific one.

A: I think one of the most amazing species is the worm-like one that lives near thermal vents. These organisms don't eat plants or animals and they don't use photosynthesis. They get their energy from breaking down the chemicals released from the vents. They live at extremely high pressures and are basically unlike anything else on Earth.

A: There may be life on other planets, but they would be so far away that it is unlikely that we will ever visit each other. How far away is the nearest solar system? How long would it take a ship to reach there if it traveled just below the speed of light? The idea of aliens has created a lot of interesting fiction because everyone can use their own imagination to decide what life on other worlds would be like. What do you think? Could there be life on planets that we couldn't inhabit? Would you want to visit them? Would some of the life forms be as smart or smarter than us? Could we communicate?

Q: If we use only 10% of our brain-what is the other 90% doing?

A: Well, we actually use a lot more than that. For a complete discussion of the "10% myth", see http://weber.u.washington.edu/~chudler/tenper.html or http://www.exn.net/Main/JaysBrain/jb-19980128.cfm. We don't use all of our brains all the time, though. If you look at images that show the active areas of the brain, you'll see that some portions are active when others aren't. Different areas are used for speaking, recognizing faces, coordination, etc.. Even though we use most of our brains, we never 'use them up'.

There's a lot we don't know about our brains. We still don't know exactly how learning and memory work, but it looks like it involves our brain cells making new connections. We don't get new cells, they just hook up in new ways. Animals that live mostly by instinct (like earthworms) have most of their brain connections pre-programmed. They can learn, but not much. We are born with very few instincts, but can learn complex new things all the time. Unless our brains are damaged by injury (wear your bike helmet), disease, drugs, or lack of oxygen, we can never use up all of our capacity to learn. In fact, the more we use our brains, the better we get at learning.

If a part of our brain is damaged, we can sometimes recover completely. This is particularly true for children under the age of 10. It seems like our memories are not stored in one place, like a book in the library, but are somehow spread through large parts of our brains.

Is it better to live by instinct and never have to learn anything, or to have to learn nearly everything? What happens if there's no one to teach a "learner"? What if you did everything by instinct and couldn't learn much, then the environment changed? Do other animals learn from their parents? Which ones do and don't? What do they have in common? Do animals that learn more live longer or shorter than average, have more or fewer offspring than average, live in certain types of environments? What do you think the connections are between these lifestyles and the ability to learn?

A: I am a biologist. Some of the jobs I've had so far include technician in a state crime lab, technician in a neurobiology lab, science teacher (high school age), outdoor education instructor at Girl Scout camp, and college biology instructor. Now I do research on how rodents deal with environments that vary.

Some of the other jobs open to biologists include human and veterinary medicine and related jobs (veterinary technician, paramedic, physical therapist, etc.), government agency work (game management, environmental protection, disease control, etc.), research for private companies (agricultural and medical research, environmental consulting, etc.), communications (producing nature programs, writing books, doing artwork for scientific publication, etc.). There are hundreds of other jobs too.

Some of the things you can do now to prepare for a biology career are: take classes in science, math, computers, and foreign languages. The more languages you know, the more places in the world you can work. There are many travel opportunities for biologists. Reading and writing skills are important too. Practice being a careful observer. Look at some of the living things in your schoolyard and local park. Try to write descriptions of them. Watch birds or mammals. What are they doing? The most important thing for a biologist to do is to ask interesting questions, so you're on the right track.

A: The color of our skin, hair, and eyes comes from pigments made by our cells. The program for making pigments (and everything else) is in our DNA. There are several genes in our DNA that tell our cells how to make and deposit pigments into our irises. If they are all "switched on" and have the pigment codes right, our eyes are a very dark brown. If only some genes are "on" and have the right directions, our eyes can be light brown or hazel. If we lack all of the pigment codes or they are shut off completely, we have blue eyes. So there are two things operating, one is the presence or absence of instructions, the other is whether the process is "switched on".

Usually both our eyes are the same color. Normally every cell in our body (with two exceptions) has exactly the same DNA. The one cell we each grew from had a specific code that was passed on to each cell that makes us up. Each cell uses only the programs it needs, but it has them all. Sometimes when copies are made, something is not copied exactly, so that the DNA in the new cells is different. This is called a mutation. This means that the DNA in some of your cells will be different from the DNA in other cells. So in the cells of one of Lindsay's irises the directions for making and depositing pigments are probably missing or turned off. Have you seen patches of different colors in coats of animals? Many animals (including people) are born with eyes, hair, and skin that are very light, even if they will later be dark. Sometimes baby animals have very different colors and patterns than adult ones. Why do you think this is?

A: On your way home from school today, look at all the tree trunks you can. What colors are they? Can you find any trees with white bark? Are there any that are green, or nearly black? There are many kinds of trees, so there are many kinds of bark. A lot of bark is a brownish-gray because the outer layer of bark is made of dead tissue. If you look at unpainted wood that has been out in the weather for a few years, you will see a similar color. Why would it be to the tree's advantage to have an outer covering of dead material?

If you painted a dot on the side of a tree and came back 10 years later, would the spot have moved up? (hint: does a swing hanging from a branch get higher off the ground year after year?) One way a tree grows is by adding parts at the ends of itself. Another is by adding layers to make it thicker. If only live cells can divide, and the outer bark is dead, where is the cell division (mitosis) happening? Try (or imagine) this, partially blow up a balloon. Clip the end closed, but don't tie it. (A binder clip should work.) Now make a 'bark' by spreading mud or a flour and water paste on the balloon. Let it dry for a while. Now blow the balloon up a little more. What happens to the 'bark'? Does this expalain the pattern of bark on some trees?

A: Hmm-When I close my eyes, I don't see black dots. We all see something though, even if it's just blackness. Our eyes don't stop working just because we close them (though our brains may ignore the signals). The eyelid itself is not uniform, so we may see ghostly images of the eye's blood vessels when we look at the light with our eyes closed. Another thing we see is after-images. If we look at something bright, we may see that shape after our eyes close. For an interesting experiment with after-images, see http://www.exploratorium.edu/publications/Snackbook/bird_in_cage/bird_in_cage.html

Q: Are you ever bored with what you are doing?

A: The really boring parts for me are the paperwork (getting permits and funding) and entering data onto the computer. In science, you generally have to do or measure the same thing repeatedly to see what happens each time. For example, if you want to know what types of plants are growing in a particular place, you have to spend a lot of time identifying and counting them. Sometimes this is dull, but then you get to look at information that NOBODY has ever seen before. Sometimes I get results that are totally different from what I expect. That's really exciting. You don't always know what the data mean when you're collecting them. Sometimes you just can't see the big picture or something is hidden from you (a "double blind" experiment). Taking a look at your data after you have spent months collecting it is like opening a surprise package. Sometimes it's exactly what you expected, sometimes it's different but even better, sometimes it's disappointing, but opening the box is always fun.

A: A lot of people would like to know the answer to that question. The Human Genome Project (http://www.ornl.gov/hgmis/) is a group of people trying to map every one of our estimated 80,000 genes. Unfortunately, that still won't answer your question. Genes are basically recipes for making us (or oak trees, or earthworms). If each gene acted like a recipe for making one dish in a meal, we would be able to answer your question as soon as we had the genes mapped. 8 recipes would make 8 dishes, right? So do 80,000 genes make 80,000 traits? Nope.

The 'gene cookbook' works more like this: You have to read 10 different recipes at once to make a salad. When you add pepper to a sauce, garlic is added to your biscuits, your lemonade turns blue, and your lasagne freezes. When you set the oven for your cake, your carrots disappear. If you follow a recipe on a cloudy day you get ice cream, on a sunny day the same recipe makes mashed potatoes. That's more like the way genes create us.

Here's why:

1. "Additive effects", meaning that many genes may work together to produce a single trait. For example, your height is determined by many different genes, but the final trait can be expressed as one number (though it will change over time). If many genes are working together, and you might have any combination of those genes, what will the *population* look like? (hint: compare this with a simple dominant trait. For example, let's say that if you have one P gene your ears will be pointy. What will a population look like if both P and p are equally numerous? Compare this with a population where many genes control ear shape.) (Many genes can = 1 trait.)

2. "Pleitropy" (PLEE-oh-troh-pee), meaning one gene can affect many things which don't even seem to be related to each other. What would happen if your body had genes that were an *incorrect* recipe for insulin? If we couldn't treat you for this disease, effects would be found from your eyes to your feet. What do we call this disease? (1 gene can = many traits.)

3. "Epistasis" (eh-PISS-tih-sis), which basically means that one set of genes interferes with another set so we don't see the trait they'd normally cause. For example, Labrador retrievers have one set of genes that produce the black pigment for the fur, skin, and eyes. Another set determines whether the pigment will actually be put into the fur. So just because a dog can make the pigment doesn't mean the trait will be *expressed* by the dog. Does a yellow lab have the genes for black pigment even though it's yellow? Could you tell by looking at it? (Hint: read this paragraph carefully, there's a clue in it.) (A few genes can = 1 trait or a few traits)

4. The effects of environment, which may change the way genes are expressed. For example, what happens if your genes code for you to be tall, but you don't get good nutrition when you're growing? (1 gene or a few genes can = one trait, but whether the trait shows up depends the environment.)

So, 80,000 genes = how many traits? Beats me, but it's an interesting question.

I know it's not the same exactly as insects, but how are they the same?

thanks for you help

A: Insect metamorphosis is pretty interesting. It takes a lot of specialized physiology and anatomy to let an animal turn from a caterpillar to a butterfly, or from a maggot to fly. This change is a lot different from the changes from early "almost humans" to humans though. Insect metamorphosis takes place during the lifetime of *one individual*. Human evolution took place by offspring being a bit different from their parents. In evolution, the *population* changes over time. In metamorphosis, an *individual* changes in its own lifetime. If people are still around in a few hundred thousand years, they might be different from us, but *individual* humans still won't be able to turn into something else.

Why do you think insects can do metamorphosis and we can't? What is the advantage of having a crawling, eating body form for part of your life and a flying, mating body form for the other part? Are there disadvantages?

As a side note, the Neanderthals went extinct for unknown reasons about 35,000 years ago. Fossils suggests that we had the same ancestors they did, but we did not evolve from them. Fossil skulls show that Neanderthals had bigger brains than we do!

I think that the quail has a little thing on thier head because that is how you can tell them apart,on the one of the deer I think that they have horns because that is what they use to fight . are there other reasons

thanks

A: You made a good connection between what you saw in deer and what you saw in quail. They are both examples of what we call "sexual dimorphism", which is just a way of saying that males and females look very different in some species. This is because female birds and mammals are picky about their mates. A female bird or mammal usually has to care for eggs and/or babies, so females can only have a limited number of offspring. In species where male care of offspring isn't necessary, male animals can mate with several females (if they get a chance).

In California quail, males and females form pairs, so both males and females only have one mate. Normally this would mean that even the poor-quality males would get a mate. Unfortunately for the males, there are always more adult males than females. This seems to be because raising young is dangerous and tiring for females. Whatever the cause, it means that some males are always left out. Males compete with each other for the chance to pair with a female. Because there are lots of males to chose from, the females can be picky. You are right that males are probably advertising themselves by looking different from females. They also have special calls and behaviors to say, "I'm an unmated male." Males that are flashy looking may be able to advertise to females and other males that they are healthy. There's a good site about his topic at: http://www.sciam.com/1998/0498issue/0498dugatkin.html

In deer, males don't take care of the young at all. No pairs are formed, so no females have to settle for a weak male. This means that a few males can be the fathers of a lot of offspring. It also means that many males don't get to mate at all. There's a lot of competition between males to be the successful fathers. You're right that males use their antlers to fight with each other. If the antlers were to protect deer against predators, females would have them too, and males would keep their antlers all year instead of shedding them.

If you were a female deer, would it be better for you to have a daughter, who is almost guaranteed a mate but will only have one fawn per year, or have a son, who might have lots of offspring, but is much more likely to have none at all? Would it make a difference if you were healthy or if you were in bad shape? What about if you were a male deer, would sons or daughters be a better choice?

Incidentally, the main difference between horns and antlers is that horns are kept all through an animal's life. Cows, bighorn sheep, and the African antelopes all have horns. Females have horns too, though they tend to be smaller. Antlers are shed each year. Male moose, deer, and elk all have antlers. The only female animals with antlers are caribou.

THANKS FOR YOUR HELP!

A: We all have hair just about everywhere on our bodies except for the palms of our hands and soles of our feet. If you look closely at each other's faces you'll see lots of fine hairs even though you're probably all way too young to shave. All mammals have hair. Even whales, which don't have fur as adults, have hair before they're born. We have about as many hair follicles per inch on our bodies as chimps do, it's just that our hair is short and fine. (Why do you think humans have so little hair? Why do we have so much hair on our heads?) There's some interesting information on hair at: http://www.oit.itd.umich.edu/bio108/anat/Hair.html

Of course, what you're really asking is about more obvious hair. Whether the hair is obvious depends on things like what color it is, how long it is, and how much of it there is. A lot of women and girls would have obvious facial hair, but they are self-conscious about it, so they get rid of it. On the other side of the coin, some adult males don't have much facial hair or only have it in patches. To answer the last part of your question, there's a lot of normal variation in hair on both males and females. Why do you think males usually have so much more facial hair than females? Why do males get facial hair, then lose hair on their heads as they get older?