In evolutionary biology, convergent evolution is the process whereby organisms not closely related genetically; independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
Another way of putting it: In Nature, similar problems will generate similar solutions, which are robust and optimal for the species. Whether it be shape or coloration or special features.
The accompanying photos of examples of convergent evolution each have a description.
Many marsupials (born in an external pouch)r in Australasia have evolved to have the same shape and physical features of their placental (born in a womb) counterparts far way. Although they are evolutionarily from two completely different lineages.
The Dendrobate genus of poisonous frogs in South and Central America have vivid colors and toxic bodies. Far away in Madagascar, the Mantella genus of frogs are similarly vividly colored and toxic. (See photo of Madagascar Mantella frog)
A Madagascan poison frog of the genus Mantella. [see previous photo of Dendrobate for description]