Glycolysis is a metabolic process that is done by all cells. However, not all cells make use of another metabolic process called the Krebs cycle. What does this tell you about the evolution of these processes?

Question

A.  As a metabolic process, glycolysis likely evolved prior to the Krebs cycle
B.  As a metabolic process, the Krebs cycle likely evolved prior to glycolysis
C.  Both the Krebs cycle and glycolysis likely evolved at the same time

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

  Gather Content
What do you already know about evolution and time? What other information is related to the question?

  Choose Answer
  Do you have all necessary information to determine the relative importance of glycolysis and the Kreb’s cycle?

  Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  As a metabolic process, glycolysis likely evolved prior to the Krebs cycle

Clarify Question
What is the key concept addressed by the question?
        · The question asks you to determine why glycolysis is used by all cells but the Krebs cycle is not.
What type of thinking is required?
        · You are being asked to break down, or analyze, why glycolysis is used by all cells but only some use the Kreb’s cycle.    

  Gather Content
What do you already know about evolution and time? What other information is related to the question?
        · Remember that evolution is a series of changes that occur over time. Evolution is shaped by several factors, including natural selection that confers greater biological fitness for a pre-existing genetic makeup within a given environment.
        · Recall also that the greater numbers of species that share a trait, the older the trait or the more important the trait may be. Given this context and considering that all organisms use glycolysis but not all use the Kreb’s cycle, what conclusions can you draw?

  Choose Answer
  Do you have all necessary information to determine the relative importance of glycolysis and the Kreb’s cycle?
        · Glycolysis is used by all cells to metabolize energy. Since it is such a widely shared trait across different life forms, it is because it is fundamentally important to survival and because it has been around for a long time in evolutionary history; certainly longer than the Kreb’s cycle, which is not used by all cells..

  Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · This question asked you to analyze the relative importance of glycolysis vs the Kreb’s cycle in evolutionary history.
        · If you got the answer correct, excellent! If you got an incorrect answer, did you remember how evolution occurs? Were you able to infer how biologically relevant glycolysis is based on its prevalence across life forms in nature? Were you able to compare its importance to the Kreb’s cycle based on this information?