Question

In a forest ecosystem, a species of bird was introduced. The birds had few predators, and for a period of time its population rose steadily and then roughly leveled off. Which of the following conclusions provides the best explanation for this phenomenon?

Answer 1

a. A predator of the birds entered the ecosystem, causing the bird population to level off.
b. Migration of birds into the ecosystem began to decline, and emigration began to increase.
c. Another species of bird was introduced, and the two species competed for nesting sites and food.
d. The ecosystem reached its carrying capacity, and was not able to support continued population growth.

Answer 2

@abhisar @Nurali can you help me?

Answer 3

@tkhunny @Nurali can you help me

Answer 4

A) Predator-prey interactions lead to an oscillating population, so A is out.
B) Immigration and emigration are possible but usually not large enough to dramatically affect an otherwise large, undisturbed population.
C) The introduction of inter-species competition is possible but is probably not the best hypothesis in the absence of other evidence.
D) A rising and leveling off of a population (sigmoidal curve) is a hallmark of a population that has reached carrying capacity. The death rate and birth rate have come to equal each other due to intra-specific competition (competition between members of the same species). This is the best answer.