Animal models have physical characteristics or suffer from illnesses similar to those seen in humans. They allow comparisons to be drawn between animal and human physiology, and help our understanding of how the human body functions. Comparative biology studies the differences and similarities between species, allowing predictions to be made, and concepts to be extrapolated from one species to another.
Models can be either spontaneous, where an animal has natural characteristics like those of humans or a human disease-state, or induced where the animal has been altered, for example, through surgery or genetic manipulation. Spontaneous models show how factors, such as diet, genetics, environment and immunity can all contribute to a disease. Induced models are useful for studying the underlying causes of a disease, and are a common research tool for identifying potential drug targets.