Which of the following statements about the factors that influence po…

The correct answer is Option (3) → When a new habitat is just being colonised, emigration may contribute more significantly to population growth than birth rates.

Population density changes through four basic processes. Births (B) and immigration (I) add individuals; deaths (D) and emigration (E) remove them. Immigration is the number of individuals of the same species that come into the habitat from elsewhere, while emigration is the number that leave it. The question asks for the incorrect statement.

Option (1) Under normal conditions, births and deaths are the most important factors influencing population density. — A correct statement. Under normal conditions births and deaths are the most important factors that change population density.

Option (2) Immigration and emigration assume importance only under special conditions. — A correct statement. The other two factors, immigration and emigration, become important only under special conditions.

Option (3) When a new habitat is just being colonised, emigration may contribute more significantly to population growth than birth rates. — An incorrect statement. When a new habitat is being colonised, it is immigration, the arrival of new individuals, that may add more to population growth than births. Emigration takes individuals away, so it can only lower the density.

Option (4) Population size keeps changing with time, depending on factors such as food availability, predation pressure and adverse weather. — A correct statement. Population size is not static. It keeps changing with food supply, predation pressure and adverse weather.

NCERT Extract:
Population Growth – “The size of a population for any species is not a static parameter. It keeps changing with time, depending on various factors including food availability, predation pressure and adverse weather.”
Population Growth – “… Under normal conditions, births and deaths are the most important factors influencing population density, the other two factors assuming importance only under special conditions. For instance, if a new habitat is just being colonised, immigration may contribute more significantly to population growth than birth rates.”