Why do this problem?
encourages students to get into the real meaning
of graphical representation without getting bogged down in
algebraic calculations or falling back into blind computation. It
will also encourage the students to think about the various
differences and similarities between growth processes in the
This problem works well in group discussion. For each idea,
try to encourage students to explain their reasoning as precisely
and clearly as possible. You could split the class into different
groups and see who can produce the most valid examples for each
- How many 'growth processes' in science can you think of. Would
any of these graphs match those processes?
- How might you label the scales for each example?
This type of problem is rich with extension possibilities. We
Extension 1: Are there
other shapes of graph which could be used to model other natural
How might you describe these curves algebraically? Can you
write down equations, the graphs of which match the shape of the
curves in this question?
Extension 2: Look up
the profile of a biphasic bacterial growth curve and understand the
conditions that produced such a curve. Wikipedia is a useful place
to start. Two clear phases of growth are seen due to:
1) The depletion of glucose from the nutrient medium
2) Transcription of $\beta$-galactosidase and associated
enzymes to allow lactose metabolism
Is there any similarity to some of
the curves given to you in the question?
Let students leaf through a science textbook searching for
graphs and charts. Do they notice that the same shapes of charts
appear frequently? Can they match any to the graphs in this