Compare and contrast homologous and analogous structures

 Analogous structures are those that have a similar function but whose origin is different. Homologous structures have the same function and also start from the same origin.

Explanation:

Convergence is the evolutionary phenomenon by which different organisms that are evolutionarily distant tend, under equivalent environmental pressures, to develop analogous characteristics.

Analogous structures are those that have a different evolutionary origin, but fulfil very similar functions. For example, the wings of a bird, the wings of a bat and the wings of an insect all are for the same thing (flight) but their phylogenetic origin is not the same. This means, they fulfill similar functions by similar means, without having the same evolutionary origin.

The development of homologous structures occurs through divergent evolution, where two related species change a common ancestral structure during their evolution in order to survive by performing different functions.

Then, if they have the same evolutionary origin, they are homologous. So, if two structures have the same function by similar means and also start from the same origin, they are homologous structures. For example, the extremities of vertebrates, similar skeletal structure, but for different uses.