Question

The diagram shows the relationships among the midge larvae(Chaoborus nyblaci), larval salamander(Ambystoma tigrinum) and two species of the crustacean Daphnia(D. rosea and the larger D. pulex) that inhabit certain pond communities. Study the relationships and deduce which of the following is/are correct.

• A. Presence of high numbers of larval salamander has an indirect effect on D. rosea and it is a positive effect
• B. When larval salamanders are present, predation reduces the population growth rate of the larger Daphnia, facilitating the coexistence of the two species of Daphnia
• C. The two species of Daphnia compete for the same resources and hence increase in resource availability will reduce the number of midge larvae and larval salamander
• D. Increase in the number of D. pulex would lead to a decrease in the number of midge larvae

Answer 1

Answer: (A), (B), (D)

The correct options are
A Presence of high numbers of larval salamander has an indirect effect on D. rosea and it is a positive effect
B When larval salamanders are present, predation reduces the population growth rate of the larger Daphnia, facilitating the coexistence of the two species of Daphnia
D Increase in the number of D. pulex would lead to a decrease in the number of midge larvae

According to the image, presence of high numbers of larval salamander will inhibit the Daphnia pulex production. This will show positive effect on D. rosea because D. pulex has negative effect on it. When larval salamanders are present, predation reduces the population growth rate of the larger Daphnia, D. pulex. This will facilitate the the coexistence of the Daphnia rosea. The two species of Daphnia compete for the same resources and hence increase in resource availability will increase the number of midge larvae and larval salamander as both species of Daphnia have positive effect. Increase in the number of D. pulex would lead to a decrease in the number of D. rosea. This in turn will reduce the number of midge larvae.

Thus, the options A, B and D are correct.