Globalized evolution...... but I might be wrong
When compared to each other, bird wings and butterfly wings can be described as ANALOGOUS STRUCTURES,
Analogous structures are those body structures in animals, which are used to perform similar functions but which have different evolutionary history. They are also called convergent structures. These structures are formed as a result of the need for the animals to adapt to similar environmental conditions. For instance, both bird and butterfly use their wings for flying.
