Biology

Alessandra Booker

14 July, 05:19

An experiment was designed to investigate the effect of caffeine on the rate of

heartbeat of fruit flies. Two populations of fruit flies were grown in a lab. Both

populations were raised drinking the same water and the same type of food. Both

populations were exposed to the same amount of light and temperature at 20

degrees Celsius. The fruit flies' heartbeats were then monitored at two hour

intervals. The fruit flies of population one were given caffeine five minutes before

their heartbeat was checked. The flies of population two were not given any

caffeine.

Which of the following is a controlled variable in this experiment?

temperature

caffeine

heart rate

experimental group