Question

Define mortality?

Answer 1

Hint: Mortality is defined as the number of deaths in the population in a given period of time. Mortality rate is expressed in units of deaths per 1000 individuals per year. Mortality contributes to the decrease of population density.

Complete answer:
The size of a population of any species is not a static parameter but it is always changing and depends upon the availability of various factors such as food availability, predation pressure and weather.
The density of a population in a given habitat depends upon the four basic processes:
Natality: Natality refers to the number of births during a given period in the population.
Mortality: It is defined as the number of deaths in the population in a given period of time.
Immigration: It is the number of individuals of the same species which come to a new habitat during the time period under consideration. Immigration helps to prevent extinction of a smaller population.
Emigration: It is the number of individuals of the population which are left that habitat and move somewhere else during the time period under consideration.
Natality and immigration contributes in growth of population density and mortality and emigration contributes in decline of population density. Mortality rate is useful in detecting the future size of the population.

Note: Plants are fixed to one place so they do not show emigration. Population density may be expressed in numbers, biomass and percent cover depending on the species. A population has many attributes (birth rate, death rate, sex ratio and age distribution) that an individual does not.