Question

You set out to observe the symbiotic relationship between a species of orchid and a species of fly. This species of orchid is only pollinated by this one species of fly, and the flies seem to prefer that orchid over any other flower for its nectar supply.

1. Propose TWO questions you would need to ask to determine the proximate causation for the species-specific preference of this fly.
2. Select ONE of the questions written above and write a hypothesis that could be tested experimentally.
3. Design a controlled laboratory procedure to test your hypothesis.

Answer 1

Question 1 : Is it the nectar of the orchid that contains some special constituent that attracts the flies?
Question 2 : Is it the colour of the orchid that attracts the flies irrespective of the nectar quality?

Hypothesis on Question 1 : The Fly species is attracted to the orchid due to a special chemical constituent in its nectar.

Controlled laboratory procedure for testing the above hypothesis :

• Two watch glasses A, B, C and D are taken.
• In watch glass A, B and C different varieties of nectar isolated from different flowers are kept. In watch glass D, nectar from the above orchid is kept.
• The glasses are placed in a closed chamber where the flies are allowed to fly freely,
• Observations were taken for which watch glass is prefered by the flies.
• If the watch glass D is the most prefered, it can be concluded that the above hypothesis is true/valid.