Answer;
He conducted an experiment with breeding pigeons.
Explanation;
The pigeons provided the perfect animal to test his theory of selection for quite a number of reasons including its trait diversity from wing structures to color patterns to size to flight patterns. From these experiments he concluded that by natural selection of randomly occurring traits that make species better suited for survival and reproduction, evolve in the astounding diversity of organisms on Earth today.
Good evening Aixa,
An experiment is designed so that you can observe the differences between the experimental group and the control group.
The experimental group is the group of specimens you're exposing to the experiment and the control group is a separate group of specimens that is not being exposed to the experiment, but are also being observed.
-Hope this helps!