(a) Name two growth models that represent population growth and draw respective growth curves y represent.
(b) State basic reason for difference in shape of se curves.
(c) Which one of curves represents human population growth at present? Do you think such a curve is sustainable? Give reason in support of your answer.

2. Logistic growth model: The growth of most population depends at least in part on the available resources in the environments. So, more realistic population growth model is the logistic growth model where population increases exponentially till it reaches the carrying capacity in the environment.
(b)  The exponential phase, gives J shape graph while sigmoid shape, is obtained in case of logistic growth. The shape of the curve differs in the two models as because in the exponential growth the population grows by fixed percent at regular intervals and the growth increases exponentially with time irrespective of the resources. In the logistic growth, the population increases at the onset and continues exponentially till the mid when the resources are utilized at maximum level. The graph becomes stationary when the population exceeds its carrying capacity.
c) The graph for the exponential model represents the current population because nowadays the population has exceeded its carrying capacity. Such kind of population growth is not sustainable because the resources of energy are limited and are about to extinct in near future which may pose threat to the upcoming generation.