Question

Read the following passage:

Populations evolve to maximise their reproductive fitness in the habitat in which they live. Ecologists suggest, the life history of organisms have evolved in relations to the constraints imposed by the biotic and abiotic components of the habitat in which they live. This gets reflected in the population growth pattern of all organisms including humans.

Study the population growth curves shown in the given graph and answer the questions that follow:

1. Identify the growth curves ‘A’ and ‘B’.     [1]
2. Mention what does the dotted line in the graph indicate and state its importance also.      [1]
   OR
   Growth curve ‘B’ shows a different pattern from that of growth curve ‘A’. Justify giving one reason.      [1]
3. 
   
   1. Which one of the two curves is more “realistic” and why?      [1]
   2. Which one of the two curves is relevant in present days with respect to human population in our country and why?     [1]

Answer 1

1. A: Exponential growth
   B: Logistic growth
2. The dotted line symbolises carrying capacity. The concept of carrying capacity refers to an ecosystem's ability to sustainably support a given population level. Understanding it contributes to the maintenance of ecological balance, the prevention of resource depletion, and the appropriate management of natural settings.
   OR
   The availability of resources is what distinguishes the logistic (B) growth curve from the exponential (A) growth curve. When resources are plentiful and unfettered, a population can expand steadily and at an accelerating rate, a phenomenon known as exponential expansion. The population size doubles over predetermined intervals in a J-shaped curve.
   On the other hand, when a population faces resource constraints, logistic expansion takes place. The population grows exponentially at first, but as resources become limited, growth slows and eventually reaches the environment's carrying capacity. An S-shaped curve is the result of this. As a result, logistic growth depicts the more realistic situation where population dynamics are influenced by resource restrictions, whereas exponential growth reflects ideal conditions with limitless resources.
3. 
   
   1. In conditions with limitless resources, populations grow exponentially or geometrically. However, no population can maintain exponential expansion indefinitely; resource constraints inevitably restrict growth. Logistic growth, represented by a sigmoid curve, is a more realistic model that reflects this inherent restriction.
   2. The logistic growth graph is more useful for the number of people living in our country right now. People's numbers have grown at an exponential rate in the past, but now resources like land, water, and energy are becoming more and more limited. As a result, population growth is more likely to follow a logistic trend because of these restrictions. This makes the growth trajectory more stable.