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Name: Amanda
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In special education class.Science project time.Topic choosen is HOW DO SCALES HELP FISH? Any suggestions or information would be of help.

Wait a minute. Why do you think the scales help the fish? How do you know they do? Have you talked to a fish lately? Maybe they are useless, or even a problem. Maybe the fish wishes it didn't have scales!

I say this only to emphasize two things: First of all, when you think scientifically, the MOST IMPORTANT thing is to be very careful not to assume you know something when you really don't. What I mean by that is: don't think you know the answer before you are dead positive absolutely for-sure 100% certain that you do. Why? Why make a big fuss over being so very careful? Well, I hate to tell you this (but you probably already know it), it's just SO EASY for human beings to fool themselves, to think they know the answers when they really don't know AT ALL what they are talking about. If you have a brother or sister, you know EXACTLY what I mean, I expect.

So scientists have learned, very painfully, that the only way to be sure you aren't missing some important fact or thinking things that are really nonsense is to be very, very doubtful about what you think is true. You must not trust what seems obvious to you. You must measure and be careful, and try to prove yourself wrong six ways from Sunday. Only if you try your very best to prove yourself wrong and you fail completely can you start to think that you might be right. Pretty tough recipe, no? But that is the only way that science advances, trust me on that. Sad but true.

OK, the second point is: when you try to answer a question like this, try to start from a clean slate. Get rid of the idea that you are talking about something you know and feel familiar with. Imagine instead you are God, designing a fish for the first time. You can do anything you want. You can make it spider-shaped or airplane-shaped or rocket-shaped. You can make its skin bumpy like a toad or furry like a bear or soft like a human baby.

What would *you* do? What seems reasonable to you? What kind of skin would you give a fish, so that it could do all the fishy kinds of things it does (live in cold water, swim fast, catch smaller fish to eat, avoid being eaten by larger fish, and so on)? Start answering your question here. Believe me, there is very little a professional ichthyologist (fish nerd) has on you at this stage, of imagining what might be the reason for scales. This is not a question of science, but imagination, and at 8 years old you have about as good an imagination as you'll ever have.

Now where the science part of this comes in is the NEXT step. Now take each of your ideas, and see what you can do to test them, see if they make sense with everything else you know. For example, let's say you decide fish should be furry to keep warm in the cold ocean. Can you think of any ``deductions'' that would result from this idea? That is, if fish should be furry to keep warm, what *else* should be true that you can check with your experience? Well, how about this: if fur would keep fish warm, then it should *also* be true that if *you* fell into the water wearing a fur coat, you would be much warmer than if you fell into the water without one. Is that true? You could do the experiment, of course, but that might be expensive. Let's see, then. How about this: suppose you went into the water with your clothes on? Clothes are not fur, but they are still something, and there's no doubt they keep you warm kind of like fur when you go outside in the cold air.

But do they keep you warm if you fall into the water or otherwise get all wet? That experiment you've probably done, and I suspect you've found, like everybody else, that the answer is NO. Wet clothes do not keep you warm. So we suspect wet fur would not either. So perhaps it would not help fish to keep warm if they had furry skin.

You can go on like this, testing each of your ideas about what kind of skin would suit fish best, and see which works with everything else you know. It might be that you can argue that nothing makes sense except scales, but that seems unlikely. Probably at the least you'll have to do a few experiments, do some tests, to see whether some of the ``deductions'' make sense which you've decided are required by certain of your ``hypotheses'' (ideas about what kinds of skin are best). Possibly you'll find that scales makes sense, but that some other ideas also make sense. For example, what about flat armor plates? That might make sense. In which case you might realize that, for example, there ARE animals that live in the water that use flat armor plate instead of scales, like crocodiles. So it might be fishes use scales instead of plates by accident. Or maybe there is a good reason, something to do with how fishes are different from crocodiles. I don't know. I haven't thought about this problem like you will.

The history of your ideas and your efforts to test them with experiments and thinking carefully would make a wonderful science project. I'd give you an A on it, that's for sure. Because it would be very scientific. Take it from me.

Now you might be bummed that I haven't given you the answer here. Sorry about that. Two reasons for that: (1) I don't have it. I don't know why fish have scales. I have *ideas*, sure, just like you and everyone else. But ideas are one thing, *knowing* is quite another. (2) I don't think the important thing here is to figure out the exact answer, even if there really is one. I think the important thing is to figure out how to GET the answer. After all, which matters more to your teacher: that you know why fish have scales, or that you know how to figure out how to answer a question like that scientifically, using your reason and the facts you already know?

Dr. Grayce


Fish scales seem to help the fish in several ways. They provide a protective covering to keep harmful things out of the fish's body. Scales allow the fish to move. Scales are hard structures, but there are so many of them and they are positioned one atop the next in such a way that they can slide past one another so the fish can move its body up and down and side to side to swim. It seems that they are also designed so that water can move across them easily so they do not slow up the fish.

Since we can not talk to fish, if there are other benefits, only the fish would know.

Steve Sample

I would like to add to Dr. Grayce' answer.

Many people think that science is absolute and finds ultimate truth. They look at science as an authority and not a process. If we carry Dr. Grayce' ideas further, we find that you get to the point where you need to make a controlled investigation. The key point is to formulate questions where you can find the answers through measurement. Once you have a clear idea of what needs to be measured, an experiment needs to be designed so that you change only one variable at a time. This is not easy to do. Often times you will find that precise measurement is difficult, at best. Sometimes you will want to isolate just one item, but find that it is too difficult to do. You may have a great idea, but no money for equipment and supplies.

Eventually, you will collect the measurements and other data necessary for your investigation. Analysis of the data is something that takes time and additional thinking. You are always looking for the hidden flaw. Once you have made it through this step, you need to develop a model that matches your observations and measurements. If you are confident about the model you have developed, you need to investigate the model to see if it withstands the rigors of further experiments. At this point, you have developed a reasonable argument for what you think is happening. This is not an ultimate truth, but rather a good approximation or interpretation of what is happening.

My imagination is not good enough to begin to answer the original question about scales and fish. I hope that as you learn more about the world around us, that you are able to design investigations that will lead us to better understanding of nature.

---Nathan A. Unterman

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