Decomposers are very important in our ecosystem, they are responsible for breaking down decaying bodies to transform into nutrients. Without decomposers, plants will not be able to get enough nutrients that it needs to grow
I'm not sure if I will answer the question you asked, as I many have interpreted it incorrectly. In natural selection, there must be variance in the gene pool, the total frequency of alleles in a population. Now, one of the organisms may have a gene that somehow helps them survive from the selective force much better compared to the others. If this does happen, over time the gene pool will narrow down to become just the genes of that organism that survived better in the first place because the rest would be taken care of by the selective force. So, the alleles and trait come from the first organisms that had the advantage over the others of its species.
Taxonomy is the science of naming and classifying organisms based on structural comparisons and genetic evidence.
