Question

the graph below shows data from an isolated population of l. lactis bacteria at two times and over a time period long enough for natural selection to occur. at the start of the time period, the l. lactis bacterias environment changed.
describe how the l. lactis population changed over this time period. use the theory of natural selection to construct a possible explanation for this change.
the percentage of bacteria with lactose - specific fermentation in the population. this suggests that bacteria with lactose - specific fermentation were likely to survive and reproduce than bacteria with polysaccharide - specific fermentation. this may have occurred because there were polysaccharides than lactose sugars after the populations environment changed. so bacteria with polysaccharide - specific fermentation had sugar they could break down than bacteria with lactose - specific fermentation.

Explanation:

• Population change: The percentage of bacteria with lactose - specific fermentation increased from about 25% to over 90% in the population.
• Survival and reproduction: Bacteria with lactose - specific fermentation were more likely to survive and reproduce.
• Environmental change: There were fewer polysaccharides than lactose sugars after the environment changed. Bacteria with polysaccharide - specific fermentation had less sugar to break down compared to those with lactose - specific fermentation.

Answer:

• The percentage of bacteria with lactose - specific fermentation increased in the population.
• Bacteria with lactose - specific fermentation were more likely to survive and reproduce than bacteria with polysaccharide - specific fermentation.
• This may have occurred because there were fewer polysaccharides than lactose sugars after the population's environment changed. So bacteria with polysaccharide - specific fermentation had less sugar they could break down than bacteria with lactose - specific fermentation.