The present population of the world is about

If the rate of addition of new members increases with respect to the individual host of the same population,then the graph obtained has:

If a population growing exponentially doubles in size in $3$ years,what is the intrinsic rate of increase $(r)$ of the population?

Zero growth means:

According to which theory will the human population outrun the food supply?

Read the following statements and determine how many of them are correct:
$(1)$ Population is the total number of individuals of a species in a given area at a given time.
$(2)$ Developed countries show a low birth rate.
$(3)$ An equal proportion of reproductive and post-reproductive age individuals indicates a stable population.
$(4)$ In the presence of limited resources,the growth curve is sigmoid ($S$-shaped).