Explain why the investigator gave the fruit flies the same type of food throughout the investigation.

The investigator gave the fruit flies the same type of food throughout the investigation to ensure that the type or quality of food did not influence the results. This makes sure that any observed changes in starvation resistance are solely due to the repeated periods of starvation, making it a fair test.

3.4.5

In Generation 1, the majority of fruit flies died from starvation within approximately 20-40 hours. By Generation 60, the population showed a significant increase in starvation resistance, with most fruit flies surviving for approximately 140-160 hours before dying from starvation. This indicates a substantial shift towards higher starvation resistance in the population over 60 generations.

3.4.6

• Within the original fruit fly population (Generation 1), there was natural variation in starvation resistance; some flies could survive longer without food than others.
• The repeated periods of food deprivation acted as a selection pressure.
• Fruit flies with higher starvation resistance were better adapted to this environment and were more likely to survive the periods of starvation.
• These surviving, more resistant fruit flies were able to reproduce and pass on their genes for increased starvation resistance to their offspring.
• Over 60 generations, this process of natural selection led to an increase in the frequency of genes for high starvation resistance in the population, resulting in an overall increase in the average starvation resistance of the fruit flies.