Final answer:
On a logistic population growth curve, growth slows down after initial exponential growth due to insufficient resources to support more individuals. This transition represents a shift from exponential to logistic growth as the population reaches the carrying capacity of the environment.
Step-by-step explanation:
On a logistic population growth curve, the growth starts to slow down after initial exponential growth because there aren't enough resources to support as many new individuals. The correct answer to fill in the blank would be a) Exponential.
Exponential growth is characterized by the number of individuals doubling at regular intervals, leading to a J-shaped curve on a graph. This occurs when resources are abundant. However, as resources begin to dwindle, the growth rate slows down and eventually levels off, resulting in a logistic growth curve that typically looks like an S-shaped curve. At this point, the population has reached what is known as the carrying capacity of the environment, where the number of individuals the environment can sustain is in balance with the available resources.
This transition from exponential to logistic growth occurs because of density-dependent factors, such as limited food or space, which become more influential as the population size increases.