Question

different l. lactis bacteria are better at fermenting different types of sugars. some l. lactis have polysaccharide - specific fermentation, so they can ferment large sugar molecules called polysaccharides but not a small sugar molecule called lactose. other l. lactis have lactose - specific fermentation; they can ferment lactose, which is found in milk, but cannot ferment polysaccharides. lactose - specific fermentation is useful for humans: it helps turn milk into cheese!
the l. lactis bacterias environment changed to have fewer polysaccharides than lactose sugars. after this change, over a time period long enough for natural selection to occur, the percentage of the l. lactis population with lactose - specific fermentation increased.
use the theory of natural selection to construct a possible explanation for how the l. lactis population adapted to its changed environment.
having lactose - specific fermentation was more advantageous than having polysaccharide - specific fermentation after the environment changed. so the alleles for polysaccharide - specific fermentation were passed on with frequency than the alleles for lactose - specific fermentation. as a result, the pr the population with polysaccharide - specific fermentation decreased. over population adapted such that a lower percentage of bacteria were dependent on the less abundant sugar.

Explanation:

In natural selection, traits that are advantageous in an environment are more likely to be passed on. Since lactose - specific fermentation was more advantageous (as the environment had more lactose), bacteria with this trait survived and reproduced better. This means alleles for lactose - specific fermentation were passed on more frequently. Bacteria with polysaccharide - specific fermentation (which was less advantageous) had lower survival and reproduction rates. So their alleles were passed on less frequently (lower frequency). As a result, the proportion of the population with polysaccharide - specific fermentation decreased. Over time, the population adapted so that a lower percentage of bacteria were dependent on the less abundant (polysaccharide) sugar.

Answer:

lower