1. Why are larger individuals of a particular species eaten more frequently than smaller ones?
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General
Thoughts
In this first
laboratory our primary interest is in your learning to perform a reasonable
investigation (observe, hypothesize, design, gather data, analyze, explain)
and to write a report. There are some interesting concepts related to probabilities,
foraging, body shape, and predator-prey relationships that you might discover
here and you will find them useful in some of our later scenarios, including
Fire and Ice, Trip to the Galapagos, and Rainbow Connection.
You might
also give some thought to the predator and prey we are using. The prey are
inanimate objects that differ in one basic way, so you have controlled for
behavioral and physiological differences among them. The experiments you design
will "work" well because we are visual predators with the same limitations
as many other vertebrate predators. Our eyes and our ability to detect and
choose among objects is constrained in the same ways as other vertebrates.
In many ways it is very interesting that we can get reliable, repeatable results.
Good hypotheses
offer an explanation concerning the mechanism (how or why (evolutionarily))
for some set of observations. Good hypotheses are testable. They lead to
specific predictions (something occurs faster, slower, more, less, etc.)
that would result if the hypotheses was the best explanation and others
if the hypothesis was unlikely to be correct. For this first lab, you have
one hypothesis given in the text and you should devise an experiment to
test it. You also need to come up with as many alternative hypotheses as
you can and figure out how to test at least one as an alternative to the
one proposed. Here are some bad ones, to help you learn what you should
be proposing. Good hypotheses can be wrong (and most are, and good experiments
test wrong hypotheses too as alternatives) but they are good because they
make sense given the observations, they take into consideration known theories,
and they can be tested.
Certain Tetra cryptoformis are harder to catch because they are more cryptic.
It is a hypothesis,
but how would you test it? What does "more cryptic" mean? If you just mean
harder to see, then that is just like the hypothesis given and is not
an alternative.
Certain Tetra cryptoformis are harder to catch.
This is a generalization
(which might be an acceptable idea to test in some other experiment),
but offers no explanation. There is nothing you are testing here.
Certain Tetra cryptoformis are harder to catch because they are faster (or slower).
You need to read
the description of the situation. These "organisms" are sedentary.
Certain Tetra cryptoformis are harder to catch because they are older.
Again this is nothing
you could test or even measure. Don't make stuff up, it has to fit the
information given.
Larger Tetra cryptoformis are willing to sacrifice themselves for the protection of smaller
ones.
There is no way to
measure "intention" among cardboard squares!!!
Larger Tetra cryptoformis are harder to catch because they are fatter.
How can you determine
that one organism is 'fatter' than another? How would you test whether
their body fat causes them to be caught more often?
Some
Worthwhile Web Sites
We haven't
had a chance to find any yet so here are the results of a search using AltaVista.
And one using Google.
