Question

Study the graph given below and answer the questions that follow :

(i) Write the status of food and space in the curves a and b.

(ii) In the absence of predators, which one of the two curves would appropriately depict the prey population ?

(iii) 'Time' has been shown on x-axis and there is a parallel dotted line above it. Give the significance of this dotted line.

Hint:

Curve a is exponential (resources unlimited), curve b is logistic (resources limited); the dotted line is the carrying capacity K.

Answer 1

Step 1: Read the graph:
The graph plots population density (N) against time (t). Curve a rises steeper and steeper without any bend. Curve b rises slowly, then fast, then flattens when it touches the dotted line.

Step 2: Status of food and space (part i):
Curve a is the exponential (J-shaped) curve. It needs food and space to be unlimited, so every individual can feed and breed freely.
Curve b is the logistic (S-shaped) curve. Here food and space are limited, so growth slows down as the population crowds the habitat.

Step 3: Curve for prey without predators (part ii):
Predators are the main check on prey numbers in nature. With no predators, the prey keeps multiplying at its full biotic potential.
That growth pattern is shown by curve a (exponential), until some other resource runs out.

Step 4: Dotted line (part iii):
The dotted line is parallel to the time axis, so population density stops rising once it reaches this level.
It marks the carrying capacity, K. This is the maximum number of individuals the environment can support with its food and space.

Final Answer:
(i) Curve a: food and space unlimited; curve b: food and space limited. (ii) Curve a. (iii) The dotted line is the carrying capacity (K) of the habitat.