© The Open Door Team
Soil Sample A
Soil Sample B
Soil Sample C
Soil Sample D
What has happened to the control Petri dish? Does this mean your results are valid or invalid?
Are there any differences between the number of colonies of micro-organisms which have grown in the four Petri dishes?
Explain any differences you observe.
When you look at soil you cannot see micro-organisms with the
naked eye. Why can you see the micro-organisms in the Petri