Compare and contrast reductionist biology with system biology.
In reductionist biology, and science in general, the approach is to limit the possible variations in what is observed by observing as little as possible at any time. In reductionist biology today, this would be studying a single protein or gene to exhaustion, observing everything that the protein does at different temperatures, under different enzymes, and in different combinations.
Systems biology is just that; the biology of a system. Rather than limiting oneself to a single thing, systems biology will apply a change to a system, from a cell to an organism, to try and elicit responses.
Often times, reductionist observations are more reproducible than systems observations, because reduced problems are far simpler and have less opportunity for error. Systems biology, however, often yields more unexpected results, and can be used to deal with interactions between things so complex that the reductionist approach would be unable to handle.