Because through natural selection, only the fittest survive. when the fittest come together and reproduce then the species continues and evolves with only the fittest and strongest genes.
Thanks to recycling, we barely mine lead any more. An estimated 85 percent of lead in use today goes into batteries, mostly for automobiles. And when the batteries run down, 99 percent of this lead is recycled to make new batteries.
-Homologous structures in different organisms
Bacteria are a prokaryotic cell, did it in class the other day