Similar organisms that are not related are an example of
a. natural selection
b. convergent evolution
c. divergent evolution
d. common ancestor

The best answer here is " B. Convergent evolution". This describes the process whereby evolutionary pressures of the local environment in two unconnected areas converge to produce organisms that are similar. This may be because they have developed solutions to sourcing their nutrition from the same type of place eg ants in a nest preyed upon by mammals with specially adapted long tongues.

Change in speed or direction : )

Not a  mixture of two common elements that can be separated by physical means.