Collecting data on algae on trees

Collecting data on algae on trees
This resource was developed by Dr Paul Davies, Institute of Education, University of London. It was
developed using information from a variety of sources, including the OPAL website
( and the Woodland Trust. ( This is
one example activity used in the session on Trees – a keystone species (see associated resource
outlining the teaching notes for the session) during a visit to Kew Gardens with PGCE Science students in
which they learned how to run activities for secondary school pupils (see associated resource : Science
outside the classroom).
Collecting data on algae on trees - activity
Look for a green powdery growth that is evidence of the presence of tiny single-celled alga called
Pleurococcus growing on the trunk.
Find out which direction is North – using a map or compass or information from your teacher. Try to
identify the direction from which the wind usually blows. This is called the ‘direction of the prevailing
Draw how the base of the tree trunk looks from the north and the south. Show where the Pleurococcus
is growing by shading on your drawing. Look closely. If you think the green patches are more dense in
some areas than others, shade those areas a little darker on your drawing.
Take your piece of string marked at 10 cm intervals. Fix it around the trunk of the tree about 1–1.5 m
above the ground (above dog height!).
Place a 10 cm x 10 cm quadrat on the string at one point. Estimate the density of Pleurococcus by
estimating the percentage of bark under the quadrat that is covered in it.
Move the quadrat along as shown in this diagram, and repeat your estimation.
This resource has been released as part of the OSIER project, which is promoting the use of resources to
support the training of practitioners in Education for Sustainable Development and Global Citizenship
within the curricula of all of the home nations of the United Kingdom. You can find out more about the
project on the ‘About’ page of the project repository site.
OSIER is part of the second round of the UK OER (Open Educational Resources) programme, funded by
HEFCE and administered by the Higher Education Academy (HEA) and the Joint Information Systems
Committee (JISC).
The resource was written by Paul Davies and copyright resides with Paul Davies and the Institute of
Education, University of London. Any images or other materials are original unless stated otherwise.
Copyright images may be excluded from the Creative Commons licence described below.
The resource is made freely available under Creative Commons licence BY-NC-SA which allows you to
use this material for any purpose as long as you:
acknowledge the original author
do not use it for commercial purposes
publish any derived materials under the same licence conditions
You can find out more about this licence at:
15th July 2011