QCA Unit 5B Life Cycles

Seed Dispersal Experiment
Experiment 1: An Experiment to Examine the Effect of Height on Wind Dispersed Seeds
Question: Is it better for plants with wind dispersed seeds to grow tall or short?
Equipment:
(for each group of 4)
Silver Birch Seeds
A sheet of A1 sized paper
Coloured pencils
A meter rule
A copy of the suggested write up format below

Method:
Discuss with the children the different types of wind dispersal, and explain that they are going to take a closer look at wind dispersal.

1) Crumble the birch seeds into a pot so the seeds are loose.
2) Place a large piece of paper on the table top.
3) Hold a meter rule upright in the middle of the paper.
4) Hold the pot of loose birch seeds to the 25cm mark on the meter rule.
5) Tip the pot, allowing the seeds to float down to the paper.
6) Using a coloured Pencil, draw around the area covered with seeds.
7) Sweep up the loose seeds and put them back in the pot.
8) Repeat the experiment but with the seeds emptied at 50cm and then 100cm.
9) Make sure you draw around the seeds with different coloured pencils each time.

Your sheet of paper should look something like a group of concentric rings.

Conclusions:
Get the children to answer the following questions:
a) Which height spread the seeds furthest, 25cm, 50cm, or 100cm?
b) Did the height have much effect?
c) Did the seeds dropped from 100cm go 4 times further
than the ones dropped from 25cm?
d) How do the conditions in the classroom differ from those outside?
e) How could we create windy conditions in the classroom?

Finally return to the first question:
Is it better for plants with wind dispersed seeds to grow tall or short?

 

Experiment 2: An Experiment to examine the effect of wind on wind dispersed seeds.
Question: How does wind affect the distance that wind dispersed seeds will travel?
Equipment:
(same as experiment 1)

Method:
Repeat experiment one with the following differences:
a) Put the paper and ruler at one end of the table.
b) The leader holds the pot of seeds next to the 100cm mark on the ruler.
c) The rest of the group stand at the other end of the table.
d) The group blow as hard as possible as the leader tips the seeds.
e) Draw around the seeds on the paper (if possible)
Conclusions:
a) Does moving air (wind) cause the seeds to be carried further?
b) Do you think it is windier at the top or the bottom of the tree?
c) Does a seed on a tall tree have more of a chance of being carried further than one on a smaller tree?
d) Look at the birch seeds under a microscope or a magnifying glass. Can you see anything about the seed that might help it float through the air more easily?
e) Draw a large picture of your seed and label it.
Finally return to the first question:
How does wind affect the distance that wind dispersed seeds will travel?

Please click here to see a suggested write up format,
which can be printed for the children to use.
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