Objects that we collect are sometimes very similar, which causes difficulties in identifying and classifying them. To overcome this hurdle, scientists and collectors often use a dichotomous key. This tool makes it possible to identify species being studied by proposing choices that make it possible to eliminate various possibilities according to their characteristics. There are many such keys to identify plant and animal species.
Here as an example is a simple key that makes it possible to identify the preceding six specimens. To proceed through the key, you must choose the better of the two descriptions proposed to go to the next step.
1 a) Animal that has at least two wings (go to 2) b) Animal without wings (go to 5 )
2 a) The body is covered with feathers (go to 3) b) The body is smooth or covered with hair, but never covered with feathers (go to 4 )
3 a) Strong, high beak, with a keratinous part Bycanistes subcylindricus b) Pointed, conical beak, never with a keratinous part Icterus galbula
4 a) The wings are opaque and covered with small, microscopic scales visible with a magnifying glass Callicore aegina b) The wings are translucent Gomphus spicatus
5 a) The animal has a developed muzzle, covered by a keratinus casing, resembling the beak of a duck; absence of teeth in the adult Ornithorhynchus anatinus b) Animal that has a short, rounded muzzle; incisors are long, pointed and strong Castor canadensis