- Final answer:
Bacteria given air grew faster because aerobic respiration provides more energy than anaerobic processes, allowing for rapid growth and an increased population size.
Step-by-step explanation:
The bacteria given air likely grew at a more rapid rate because they were performing aerobic respiration, which is more efficient at generating energy (ATP) than anaerobic processes utilized by bacteria without air. Oxygen serves as a final electron acceptor in the electron transport chain during aerobic respiration, allowing for a more complete oxidation of glucose, which results in more ATP produced than through fermentation or anaerobic respiration. Those bacteria that can use oxygen are therefore able to grow faster and have a more prolific increase in population size than the bacteria that cannot use oxygen.
In tube A, the bacteria are obligate (strict) aerobes that require abundant oxygen to grow. In tube B, the bacteria are obligate anaerobes, which are killed by oxygen. Tube C contains facultative anaerobes that can grow in the presence or absence of oxygen. Tube D has aerotolerant anaerobes that are indifferent to oxygen. Tube E contains microaerophiles that require a specific level of oxygen for growth. Bacteria in tube B, the obligate anaerobes, will grow more rapidly in an environment without air compared to tube A, the obligate aerobes that require oxygen to grow.