The existence of similar biochemical pathways is the main biochemical evidence of evolution. Many organisms, including prokaryotes and eukaryotes, share common biochemical pathways controlled by homologous enzymes. In particular, biochemical pathways that regulate energy metabolism represent a good evidence of evolution. For instance, glycolysis is a process of glucose transformation that is observed on all living organisms. The proces is associated with the breakdown of sugars and ATP production. Bacteria that are the oldest organisms and evolved in the conditions of the lack of oxygen, use glycolysis to produce ATP. Glycolysis is the first step of fermentation that does not require oxygen. In contrast, eukaryotes that evolved later use oxygen for respiration and production of ATP, although glycolysis remains the main source of ATP under anaerobic conditions and is the first step of aerobic oxidation of glucose. These features demonstrate that biochemical pathways evolved in response to environmental alterations while glycolysis remained that major pathway of the transformation of sugars in prokaryotes and eukaryotes supporting the idea of evolution.