Animal models (in English only)
Where a researcher wants to study a specific biological phenomenon, such as the development of a specific human disease, an animal model can be used.

An animal model is a living animal in which pathological processes, or biological or behavioural characteristics, can be studied. In the animal being used as a model the studied phenomenon resembles the corresponding phenomenon in the target species.

Normally, the target is the human species. However, animal models can be used to study biological phenomena in other animal species (and indeed the species of the animal being modelled).

It is important to realize that an animal model will not resemble the target species in every way: just one or a few characteristics are believed to be similar in the model and the target subject.

In humans, for example, a fat-rich diet will activate a component of the coagulation system called factor VII. Whether this affects the risk of thrombosis is an interesting research question.

In this scenario two models are considered: pigs and rats. The physiology and metabolism of the pig seems to model human physiology more closely than the rat. But it has been found that a fat-rich diet does not give a rise in factor VII after a meal in the pig, whereas in rats this does happen – just as it does in humans.

So the human phenomenon of raised factor VII in the blood after a fat-rich meal can only be scrutinized with a rat model. The pig, failing to display this specific phenomenon, is not a suitable model.