Question

What do ‘a’ and ‘b’ represent in the following population growth curve?

• A. ‘a’ represents exponential growth when responses are not limiting the growth; and ‘b’ represents logistic growth when responses are limiting the growth.
• B. ‘a’ represents logistic grwoth when responses are not limiting the growth; ‘b’ represnrs exponential growth when responses are limiting the growth.
• C. ‘a’ represents carrying capacity and ‘b’ shows logistic growth when responses are limiting the growth.
• D. ‘a’ represents exponential growth when responses are not limiting the growth and ‘b’ shows carrying capacity

Answer 1

The Correct Option is A

The question involves understanding a population growth curve, which is a fundamental concept in ecology. The curve generally illustrates how a population grows over time under different environmental conditions.

1. Exponential Growth (‘a’):
   • This is represented by the equation \(\frac{dN}{dt} = rN\), where N is the population size, r is the intrinsic growth rate, and t is time.
   • Exponential growth occurs when resources are abundant, meaning the population is not limited by the environment. It results in a J-shaped curve as the growth accelerates over time.
2. Logistic Growth (‘b’):
   • This is described by the equation \(\frac{dN}{dt} = rN\left(\frac{K-N}{K}\right)\), where K is the carrying capacity of the environment.
   • Logistic growth takes place when the population’s growth is limited by environmental factors such as food supply or habitat space. It results in an S-shaped (sigmoid) curve. Here, the growth rate declines as the population size approaches the carrying capacity.

Given these definitions, the correct interpretation of the graph is:

• ‘a’ represents the exponential growth phase where resources are not limiting the growth.
• ‘b’ represents the logistic growth phase where resources constrain further growth, and the population reaches carrying capacity.

Therefore, the correct answer is: ‘a’ represents exponential growth when responses are not limiting the growth; and ‘b’ represents logistic growth when responses are limiting the growth.