Glossary
Access to Family Planning
The availability of contraception and reproductive health services, which empowers individuals to make informed decisions about family size and spacing of children.
Example:
Increased access to family planning often correlates with lower total fertility rates and improved women's health outcomes globally.
Annual Percent Change (Population)
A formula used to calculate the net change in a population's size over a year, expressed as a percentage of the total population.
Example:
Ecologists might use the annual percent change formula to track how a wolf population is fluctuating in a national park, considering births, deaths, immigration, and emigration.
Birth Rates
The number of live births per 1000 people in a population per year.
Example:
A country with a high birth rate might see its population grow rapidly, even if death rates are also high.
Death Rates
The number of deaths per 1000 people in a population per year. This often includes the Infant Mortality Rate.
Example:
Improved healthcare and sanitation can significantly lower a nation's death rates, leading to population growth.
Density-Dependent Factors
Limiting factors whose impact on a population increases as the population density increases.
Example:
The spread of a highly contagious disease is a density-dependent factor because it will spread much more rapidly in a crowded city than in a sparsely populated rural area.
Density-Independent Factors
Limiting factors that affect population growth regardless of the population's size or density.
Example:
A sudden, severe wildfire is a density-independent factor that can decimate a deer population, whether it's small and scattered or large and concentrated.
Doubling Time
The amount of time it takes for a population to double in size, assuming a constant growth rate.
Example:
If a bacterial colony has a doubling time of 20 minutes, it will go from 100 cells to 200 cells in that short period.
Emigration
The movement of individuals *out of* a population to another area.
Example:
Economic hardship or political instability can cause a large emigration of people from a country.
Exponential Human Population Growth
A pattern of population growth where the population increases at a fixed percentage per unit of time, leading to a rapid and accelerating increase in total numbers.
Example:
After the Industrial Revolution, human population experienced exponential human population growth due to advances in medicine and food production, leading to billions more people on Earth.
Immigration
The movement of individuals *into* a population from another area.
Example:
A city experiencing a boom in tech jobs might see a significant increase in immigration as people move there for work.
Infant Mortality Rate
The number of deaths of infants under one year old per 1000 live births. It serves as a key indicator of a society's overall health and development.
Example:
Countries with poor access to clean water and medical care often have high infant mortality rates.
Population Growth Rate
The rate at which a population is increasing or decreasing in size, typically expressed as a percentage or a decimal, calculated from initial and final population sizes.
Example:
A high population growth rate in an invasive species can quickly overwhelm native ecosystems and outcompete local species.
Rule of 70
A simple formula used to estimate the doubling time of a population or any quantity growing at a constant annual percentage rate.
Example:
Using the Rule of 70, if a country's economy grows at 7% annually, its GDP will approximately double in 10 years.