Experiment - Variations Among Individuals

Variations Among Individuals

Purpose:
You will do sampling to study variations among individuals of a species, then compare and make predictions about variations using graphs.

Supplies:
handful of peanuts in shells
5 cats
ruler

Make a data table to record the lengths of the peanut halves, hand spreads, and cat leg lengths.

Shell each of the peanuts, discarding the shells (don't eat too many).

Remove the thin brown seed coat from each peanut, split in half, saving the larger half. Measure, in millimeters, the length of each of the halves in your sample, and record your data.

Stretch out the fingers of your right hand so they lie flat on a table or desk top. Measure the distance, in centimeters, from the tip of your thumb to the tip of your little finger. Record your data.

For each cat, gently measure, in centimeters, the length of its right rear leg, from the tip of the paw along the bottom to the joint that meets at a right angle. Record your data.

Results, Questions:
1. Construct graphs of the data for peanut length, hand spread, and cat leg length. The number of individuals doing the experiment (the more the better) is the label for the y axis. How do the graphs for hand spread and cat leg length compare to the peanut graph?

2. If you were to measure and plot the lengths of 500 cat leg lengths, what shape would you expect the graph to be?

3. If you were to measure and plot the lengths of the hands of 300 students, what shape would you expect the graph to be?

Applications:
1. How can a scientist tell from looking at a graph if a sample is large enough to provide an accurate interpretation of results? (the smaller the fluctuation in data, the better the sample)

2. What do graphs of the general shape you observed in this activity indicate about the pattern of variation among individuals of a species?