Study the given food web. Which of the following would lead to decrease in the water snail population?

P. Increase in Hydrilla population
Q. Increase in young tadpole population
R. Decrease in kingfisher population
S. Increase in dragonfly nymphs population

Options

A. Q only
B. P and R only
C. Q, R and S only
D. S only

Explanation

According to the given food web, fish feed on young tadpoles and also on water snails. So, if there is an increase in the population of tadpoles, the population of fish will increase leading to decrease in the population of water snails. Kingfishers feed on fish and fish feed on water snails. So, if there is decrease in the kingfisher population, there will be increase in fish population leading to decrease in the population of water snails. As the dragonfly nymphs feed on water snails, thus, increase in their population will lead to decrease in water snail population.