Here is an idea for an experiment. Perhaps once you have read through it you can come up with your own. It follows the scientific method and involves two different organisms.
When I put amoebas and paramecia (two types of freshwater single-celled organisms) together in a tank, after a week there are very few amoebas left, and a lot of paramecia.
The paramecia are better able to compete for the resources in the tank (such as food) than the amoebas are. Because there is ...
The expert designs an experiment using the scientific method.