Many diverse species call The Great Rift Valley home.
To answer questions like these, scientists set up different kinds of research systems. A laboratory model and a field study are two very different methods for experimentation, each with its own set of benefits and limitations. When using an experiment to gather data, it is important to recognize the variable you want to study. A variable is the condition you change in order to learn how that change affects a specimen. The control is a specimen that remains under normal, or controlled, conditions.