Investigating adaptation and defence: What determines the number of spines on a holly leaf?
Student Sheet
Preparing for the activity
Read through the Student Activity Guide and consider the following questions.
Analysis of activity
1. What is the aim of the activity?
2. What is being varied in the activity?
3. What work was previously carried out to obtain the leaves?
4. What measurements are you going to make?
5. Getting organised for experimental work
6. Your teacher/lecturer may ask you to do this activity individually. If you are part of a group, decide how the activity will be managed by allocating tasks to each member. It is important that you play an active part in collecting results.
Recording of Data
Prepare a table to record your results. You should use a ruler, correct headings and appropriate units.
Evaluation
Consider the following:
1. Why the number of spines on a number of leaves were counted at each chosen height?
2. Were the heights chosen appropriate to reach an accurate conclusion?
3. Were the leaves used chosen at random? Why might this be important?
4. Which possible variables were controlled? Why was it important to control them?
5. Which variables in the leaves has it not been possible to control? How important do you think these variables are?
Background Information
· Holly leaves are capable of producing spines. This investigation is being carried out to see if there is a relationship between the number of spines on a leaf and its height above the ground.
· To do this, small branches of holly have been cut at different heights from a large unpruned holly tree. You will randomly choose a number of leaves from each height and calculate the average number of spines that leaves from each chosen height will have.
Equipment and materials
Materials required by each student/group
Holly leaves from a range of heights. The height at which each branch/batch of leaves was obtained should be clearly noted.
Instructions
1. Collect branches/batches of holly leaves. The height above ground at which each branch/batch of leaves was obtained should be clearly noted.
2. Select, say, 10 leaves at random from one branch/batch, count the number of spines on each leaf and calculate the average number of spines per leaf in each batch.
3. Note your results in a suitable table.
4. Repeat this procedure with each available branch/batch of leaves.
5. Present your results as a graph with suitable scales and axes with quantities and units
Science & Plants for Schools: www.saps.org.uk
The number of spines on a holly leaf: p. 2
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.