List any three important characteristics of a population and explain
Three important characteristics of a population are: Population size and population density Birth or natality rate Death or mortality rate. Population size: It is the actual number of individuals in the population. The size of the population keeps changing with time depending on the factors like: (a) Food availability (b) Weather (c) Predation pressure and (d) Competition. Population density is a measure of population size per unit area. The population density in a given habitat during a given period changes due to four basic processes, namely Natality, Mortality, Immigration and Emigration. While natality and immigration contribute to an increase in the size and density of a population, mortality and emigration contribute to a decrease in them. So the equation for population growth is: Nt + 1 = Nt + [(B + I) – (D + E)], where Nt = population density at time t. B = No of birth I = No of Immigration D = No of death E = No of emigration If B + I is more than D – E, the population density increases. If B + I is less than D – E, the population density decreases. Birth or Natality rate. It is generally expressed as the number of births per 1,000 individuals of a population per year. It increases the population size (total number of individuals of a population) and population density. Natal or Birth Rate =Death or Mortality rate. It is the opposite of the natality rate. It is commonly expressed as the number of deaths per 1,000 individuals of a population per year
