 Another way that Novak and Doolittle see individual species concepts (patchworks for them) working together is that they describe the different processes that cause the existence of genetic and phenotypic clusters of organisms (in other words, basal taxa). For instance, the Biological Species Concept focuses on the exchange of genes among the members of a group, while the Ecological Species Concept focuses on the how selection affects those organisms. According Novak and Doolittle, most microorganism clusters are the result of both processes to varying degrees. These are cases where the Biological Species Concept and the Ecological Species Concept work together in helping us understand what causes those clusters.