Fish Scales and Science
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
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?
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
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
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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Update: June 2012