How Height of Leaves on Holly Bush Affect Prickliness – Biology IAA

Within this post will be all you need to know for this IAA experiment. Once again, this experiment is boring and simple which means there must be no slip up in the method at all.

Firstly, we got to know what the independent variable and dependant variable is:

Independent variable – height of the holly bush
Dependant variable – length of leaves and prickliness


Independent variable) causes a change in (Dependent Variable) and it isn’t possible that (Dependent Variable) could cause a change in (Independent Variable). So, the height of the holly bush causes a change in the the length of leaves and prickliness.


Remember when setting out the graph, the independent variable ALWAYS goes on the ‘x’ axis while dependant ALWAYS goes on the ‘y’ axis. So for this case, the height of the holly bush would be on the ‘x’ axis and the length of leaves or average prickliness (I done average prickliness) is on the ‘y’ axis, because that is the variable you are not changing.

 

How to measure prickliness

Number of pricks X height of tallest prick
So, if a leaf had 10 spines/pricks and the longest spine/prick was 1cm, to work out prickliness, you would do 10 X 1 which would give a prickliness of 10 for that leaf.

Method

  1. Identify a holly bush.
  2. Using you hands, remove 10 leaves that are around the same length, size and colour at ground level from the outer bush.
  3. Repeat step 2) but one meter up using a meter ruler to measure this, then two meters up.
  4. Separate leaves into groups to help prevent leaves from being categorized wrong.
  5. Using a 30cm ruler, measure leaves length ways to 1 decimal place and record results.
  6. Measure the size of the longest prick on each leaf to 1 decimal place. Count the number of pricks on the leaf and times that number by the longest prick number. Record results.
  7. Repeat steps 1-6 three times using different selection of leaves from the same holly bush at the same height.
  8. Repeat steps 1-6 three times using 3 different holly bushes, all the same species found in the same area and time.
  9. Ignore any anomalous data and repeat experiment to compensate for this.Your graph should look something similar to this:



The method was made valid by (The point/Explanation for the point)
Using the same 30cm ruler and meter ruler so results are recorded accurately
Use same person measuring as eye sight may differ affecting results
Same species of holly bush as different species will have different lengths of leaves and pricks
Location of the holly bush so that the three holy bushes we tested weren’t different in any way due to the environment
When we measure sample as leaf and prick size may differ in different seasons 
Time of day we picked the leaves so the leaves are at the same growth.


The method was made reliable by
Measuring length of leaves and longest prick to one decimal place
Repeating the experiment
Ignoring any anomalous results and repeating to compensate
Measuring 10 leaves instead of 1
Way in which we removed the leaves
Placing leaves into groups to stop confusion

Conclusion
(this is where you should use your results and scientific knowledge)
As the leaves were collected further up the holly bush, the prickliness decreases. At 0 metres, the average prickliness was 226 while 2 metres up it was only 88 metres. This is to stop herbivores from grazing on the holly bush so the prickliness is higher to defend the bush against these herbivores.The holly leaves were longest at the top to get as much surface area for photosynthesis.

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