Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources (for example, a heterotroph with a varied diet). A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either group, however. Some species are highly specialized (the most extreme case being monophagy), others less so, while some can tolerate many different environments. In other words, there is a continuum from highly specialized to broadly generalist species.
Omnivores are usually generalists. Herbivores are often specialists, but those that eat a variety of plants may be considered generalists. A well-known example of a specialist animal is the koala, which subsists almost entirely on eucalyptus leaves. The raccoon is a generalist because it has a natural range that includes most of North and Central America, and it is omnivorous, eating berries, insects, eggs and small animals. Monophagous organisms feed exclusively or nearly so on a single other species.
