Exponential growth of a species can be expressed as:

$I.$ Populations evolve to maximize their reproductive fitness,also called Darwinian reproductive fitness (higher $r$ value),in the habitat in which they live.
$II.$ The population growth rate $r$ is inversely related to generation time.
$III.$ The housefly,which has a short life span and produces a large number of eggs,could be considered as a '$K$' selected species.
$IV.$ Under a particular set of selection pressures,organisms evolve towards the most efficient reproductive strategies.
$V.$ Life history traits of organisms have evolved in relation to the constraints imposed by biotic and abiotic factors in their habitat.
Select the combination of correct statements.

Population growth of a country depends upon

The natural growth rate of population is checked by certain factors. These are known as

The present population of the world is about

$A$ population of $Paramecium$ $caudatum$ was grown in a culture medium. After $5$ days,the culture medium became overcrowded with $Paramecium$ and had depleted nutrients. What will happen to the population,and what type of growth curve will the population attain? Describe the growth curve.