Biologists think that speciation generally occurs when: (i) mutation leads to genetic divergence between the two populations, (ii) a barrier prevents gene flow between two populations of the same species, (iii) pre-zygotic or post-zygotic isolating barriers evolve, (iv) selection or genetic drift leads to genetic differences among the two populations.

The answer is: a barrier prevents gene flow between two populations of the same species.

cellular respiration oxidizes food into energy in the form of atps.

glycolysis (6 c hexose) > 2x atps are used > 6c hexose biphosphate > 2 x 3c triphosphate >

2 x 3c pyruvate (2x nadh produced from nad) and (4x atp produced)

pyruvate actively pumped mitochondrial matrix.