Examples of competition

Example	What it looks like
Paramecium aurelia and P. caudatum: In a classic study in the 1930’s, Gauss cultured P. aurelia and P. caudatum both alone and together in culture tubes. When grown separately, the populations grew to a fairly predictable density. However, when grown together, P. caudatum always lost and eventually went extinct.
Usually, however, when two similar species co-exist, they will start to specialize in their habitats and feeding habits and undergo character displacement to reduce the severity of interspecific competition. This is demonstrated by Galapagos finches described by Charles Darwin. The ancestral bird from the mainland of Ecuador had an intermediate-sized beak to consume insects and seeds of all sizes. Notice, however, how the break size has changed, to reflect specialization in feeding habits. (In fact, there is one finch, the woodpecker finch, which uses a twig as a tool to dig out insects from holes in trees.)