Background for Teachers
What is the scientific method?
The scientific method is a way of learning
about how the world around us works. Basically, it
goes like this: ask a question; think of some
possible answers; decide what additional facts are
required to rule out some of the possibilities;
get the facts; see what the answer turns out to
be. As you can see, facts are the key. Much of
science is about being sure of the facts.
In this unit, your students will ask a question
about the development of a baby chick, and see if
they can answer it. Of course, real scientific
inquiry - research - is a bit more complicated.
For example, we often start by just looking at
lots of data - observations - to see what
questions come to mind. And the questions and
possible answers may change as we go along,
depending on our preliminary findings. Finally,
before we start any scientific research project,
it is always good to check the library to see if
someone else has already answered our
Using the scientific method for the MRI project
First, encourage your students to make some
observations. The eye of the developing chick is
very prominent after day five. The
eyes are large and round. This is distinctive among
birds. In some MRI views you will notice that eyes
tend to have a well-defined boundary.
Now, ask the question to your students. Do the
eyes of the chick grow steadily over the whole
incubation period, or do they grow in spurts?
(Similar questions could be asked about other chick
Possible hypotheses you can discuss with your
students (these are hypothetical as we don't have
any facts yet):
- Growth is steady, the diameter increases by a constant
amount every day.
- Growth is steady, the volume increases by a constant
amount every day.
[Ask your students how this question differs from the
- Most of the growth occurs in the first week, and very
little after that.
- Most of the growth occurs in the last week.
The required facts (or observations) by your
students: Measure the size of the eyes on as many
images as possible during the incubation
period. Show how these measurements can be used to
distinguish among the four hypotheses suggested (and
any others your students come up with).
Now comes the hard part - getting the facts. A
"brainstorming" session might be in order here with
your students. One possibility: incubate 21
eggs. Crack an egg each day, and measure the
embryo's eyes (messy and wasteful, and are all those
chickens growing at the same rate?). MRI is a way of
seeing into the egg without breaking it. So a new
set of pictures can be made every day on the
chick. And the pictures can be measured accurately
through image analysis. But the pictures of MRI are
"slices" - they don't show the entire egg all at
once - so your students will have to be careful in
analyzing and interpreting them.
Implementing the MRI project
For this activity, the images your students will
work with are all side views of the egg. These
images were acquired by students (from the previous
Chickscope project), which are now archived in the
MRI database. These images are not perfect. At the
end of this unit, you may want your students to
suggest a strategy for getting better data for use
in the upcoming project.
As you might have guessed, the chick embryo moves
a lot. Unlike humans, it cannot be told to hold
still. So, often, the images will have vertical
streaks or blurring. This is generally referred to
as "motion artifact", and makes it hard to get a
good measurement (or even to find the eye!).
Furthermore, if we were to repeat the same slice
over and over, it may look different each time. For
example, the chick may turn its head causing you to
slice through the eye at the edge rather than
straight through the middle. Alas, some things even
scientists just cannot control; these things must be
taken into consideration by your students when they
begin interpreting the data.
The first step for your students is to examine
the images that you have been given for this lesson
and identify the eye in those images. This may
involve the students using the scientific method,
too: hypothesis - this round spot is the eye;
hypothesis tests - is the appearance consistent with
other pictures in the series? Is the other eye
visible in a reasonable location? Is the overall
location consistent? (The chick tends to stay at
the top of the egg, and the head tends to stay near
the air cell, particularly later in
Your students can also work with the selected
data by downloading the images to their computers
and proceed with the analysis as described in the
suggested Lesson plan.
Most likely, the results by your students will be
inconclusive. Discuss why. Your students may wish
they had better data. Ask them to think about how to
get more accurate measurements, or to compensate for
the expected lack of accuracy.