Genetic variation is when there are many offspring with different genetics, therefore some offspring might be able to adapt due to its genetics
Homologous evolution means divergent evolution.
it is a type of evolution in which different species have common ancestor. for example if we take members of one species and put them in different environments then it is observed that there is some changes in the species according to environment
analogues evolution means convergent evolution
The answer you are looking for is “Drought”.