Studying Human Populations

Studying Human Populations

• Demography involves studying populations, with a focus on human populations.
• Age structure refers to the distribution of ages within a specific population at a given time.
• A population pyramid, a double-sided bar graph, illustrates age structure.
• Survivorship is the percentage of group members likely to survive to any given age.
• Fertility rate measures the number of babies born each year per 1,000 women in a population.
• Migration is the movement of individuals between different areas.
• Life expectancy is the average number of years a person is likely to live, heavily influenced by infant mortality.
• Demographic transition models how population changes occur, based on observations from developed countries' history.
• In the last 200 years, the human population experienced rapid growth, specifically exponential growth in the 1800s, with increasing growth rates each decade.
• Scientists use age structure, survivorship, fertility rates, and migration to predict population size.
• A population with more young people than older people is likely to increase as the young people grow and have children.
• Countries with even age distributions experience little to no growth.
• Preindustrial populations have high birth and death rates, resulting in a stable population.
• Transitional populations experience a population explosion as death rates decline due to improvements in hygiene, nutrition, and education, while birth rates remain high, potentially doubling the population in under 30 years.
• In industrial populations, the birth rate decreases, causing population growth to slow, and the population stabilizes as the birth rate approaches the death rate.
• Postindustrial populations see the birth rate drop below replacement level, leading to a population decrease.
• Life expectancy is higher in developed countries with access to education, health, medicine, fuel, and clean water.
• Not all countries follow the demographic transition pattern due to variations in death and birth rate changes and differing life expectancies based on a country's level of development.

Changing Population Trends

• Infrastructure includes basic facilities and services supporting a community, such as public water supplies, sewer lines, power plants, roads, subways, schools, and hospitals.
• Arable land is land that can be used for growing crops.
• Urbanization refers to more people living in cities than in rural areas.
• Least Developed Countries show few signs of development and may have increasing death rates alongside high birth rates; they are officially recognized by the United Nations.
• Rapid human population growth causes shortages of fuelwood because it does not accumulate quickly enough for burning, leading to deforestation as people cut down wood.
• Unsafe water, in areas lacking infrastructure, can lead to the use of local water supplies for both drinking and sewage disposal, causing the spread of bacteria and diseases such as dysentery, typhoid, and cholera.
• Population growth impacts land as people seek easy access to resources and comfortable lifestyles, leading to shortages of land for growing crops and increased urbanization.
• More developed countries have a more stable and steady population growth rate.
• Less developed countries exhibit increasing death rates alongside high birth rates.
• Worldwide fertility rates are projected to decline to replacement level by 2050.
• High or low growth rates would result from varied fertility rates, estimating a world population of 9 billion by 2050.
• Less developed countries may struggle to imitate the development of the world's economic leaders if their population continues to increase.
• Some countries have implemented strategies such as family planning programs, economic incentives, and legal punishments to reduce population growth.
• Simply changing birth rates is not be sufficient to cause a nation to undergo further development.
• Population cycles will eventually reset and start increasing again.