Population dynamics
Population dynamics is the branch of life sciences
Life sciences
The life sciences comprise the fields of science that involve the scientific study of living organisms, like plants, animals, and human beings. While biology remains the centerpiece of the life sciences, technological advances in molecular biology and biotechnology have led to a burgeoning of...

 that studies short-term and long-term changes in the size and age composition of population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

s, and the biological
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

 and environmental
Environment (biophysical)
The biophysical environment is the combined modeling of the physical environment and the biological life forms within the environment, and includes all variables, parameters as well as conditions and modes inside the Earth's biosphere. The biophysical environment can be divided into two categories:...

 processes influencing those changes. Population dynamics deals with the way populations are affected by birth
Birth rate
Crude birth rate is the nativity or childbirths per 1,000 people per year . Another word used interchangeably with "birth rate" is "natality". When the crude birth rate is subtracted from the crude death rate, it reveals the rate of natural increase...

 and death rates, and by immigration
Immigration is the act of foreigners passing or coming into a country for the purpose of permanent residence...

 and emigration
Emigration is the act of leaving one's country or region to settle in another. It is the same as immigration but from the perspective of the country of origin. Human movement before the establishment of political boundaries or within one state is termed migration. There are many reasons why people...

, and studies topics such as ageing populations or population decline
Population decline
Population decline can refer to the decline in population of any organism, but this article refers to population decline in humans. It is a term usually used to describe any great reduction in a human population...


The mathematical model often viewed as the best to govern the population dynamics of any given species is called the exponential model.