The numerous chemical reactions that occur in living cells can be disrupted if conditions are too acidic or too basic. Cells are equipped to counteract such changes with substances called___ , which can neutralize acidic or basic compounds that enter the system. This response keeps the cells in an optimum range, where life functions can be carried out most effectively.

Which of the following factors would not contribute to allopatric speciation? a) a population becomes geographically isolated from the parent population. b) the separated population is small, and genetic drift occurs. c) the isolated population is exposed to different selection pressures than the ancestral population. d) different mutations begin to distinguish the gene pools of the separated populations. e) gene flow between the two populations is extensive.