In evolutionary biology, convergent evolution describes the process whereby organisms not closely related independently acquire similar characteristics while evolving in separate and sometimes varying ecosystems.
An example of convergent evolution is the similar nature of the wings of insects, birds, and bats. All three serve the same function and are similar in structure, but each evolved independently. Eyes also evolved independently in various animals.
Convergent evolution is a different phenomenon than evolutionary relay and parallel evolution. Similar to convergent evolution, evolutionary relay describes how independent species acquire similar characteristics through their evolution in similar ecosystems, but not at the same time (dorsal fins of extinct ichthyosaurs and sharks). Parallel evolution occurs when two independent species evolve together at the same time in the same ecospace and acquire similar characteristics (extinct browsing-horses and extinct paleotheres ).
Another example is the aerial rootlets found in English ivy (Hedera helix) and wintercreeper (Euonymus fortunei) (and other vines). These rootlets are not derived from a common ancestor, but developed independently as an effective way to cling to whatever support the vine is climbing on.
The smelling organs of the terrestrial Coconut crab also developed similar to insects due to the need to detect smells in the air.