Question

A food web in a certain ecosystem consists of seals that feed on krill, which in turn feed on phytoplankton. Extensive krill fishing reduces the krill population rapidly. What would be observed in the ecosystem as an immediate effect of this?
A) The seals would decrease in number and the phytoplankton would increase in number.
B) The phytoplankton would decrease rapidly, because the seals would now feed exclusively on them.
C) This would have no effect on the phytoplankton population as they just need sunlight to survive.
D) The seals would increase in number because the lack of krill would mean less competition for food.
Eliminate

Answer 1

The correct answer is - A) The seals would decrease in number and the phytoplankton would increase in number.

The significant reduction of the populations of krill in the ecosystem, will have different effects on different organisms, depending on their role in the ecosystem.

The phytoplankton is losing its natural predator with the decreasing of the krill population, so its numbers are increasing are rapidly.

The seals, on the other hand, are dependent on the krill as a food source, so with the big drop of the krill population, the seals come into a situation where they lack their food source. The lack of food source will contribute to the dying out of lot of seals, and also reducing the number of new born seals.