Question

Fruit flies have sensory receptors that respond to different chemicals. Some of these receptors are sensitive to chemicals that make up odors while others are sensitive to chemicals that make up tastes. For example, one type of taste receptor in fruit flies is sensitive to the taste of water. Scientists performed an experiment to examine the role of odor and taste receptors in guiding the behavior of fruit flies.

The scientists' experiment took place in two phases. In the training phase, the scientists kept the fruit flies away from water for 16 hours. Then, they placed the fruit flies in a chamber filled with a specific odor (odor 1) but no water for 2 minutes. They next transferred the flies to a second chamber filled with a different odor (odor 2) and water for 2 minutes.

In the next phase, the scientists tested the fruit flies by placing them in a testing maze with two arms, one of which contained odor 1 and the second which contained odor 2. Neither of these arms contained water. The scientists counted the number of flies that went into each arm. The testing phase was completed after different amounts of time had passed after the training phase. The scientists then repeated this experiment with flies that lacked the taste receptor for water. The table below shows the number of flies that went into each arm in all of the trials.

Time After Training Normal Flies Flies That Cannot Taste Water
Odor 1 Odor 2 Odor 1 Odor 2
3 minutes 36 64 55 45
3 hours 33 67 45 55
24 hours 30 70 51 49
Data adapted from Shyu et al. 2017. Nature Communications. Licensed under CC BY 4.0.

How do the scientists' findings support the argument that the information fruit flies take in through their sensory receptors can be stored as memories?
A.
by showing that more of the fruit flies that could taste water were attracted to odor 2 than odor 1 at 24 hours after training
B.
by showing that fruit flies that could not taste water were less likely to locate water in the maze than fruit flies that could taste water
C.
by showing that fruit flies that could not taste water were not attracted to odor 2 by 24 hours after training
D.
by showing that fruit flies that could taste water were more attracted to odor 2 during the training period than were fruit flies that could not taste water

Answer 1

A

Normal flies showed a clear preference for odor 2 even 24 hours after training (30 vs. 70), indicating they retained the odor–water association as a memory. Flies lacking the water taste receptor did not show that lasting preference.