Human Demographics

• Demographics of populations include statistical data relating to populations
• Human populations fall under demography, while plants and animals fall under population ecology
• Populations change over time depending on birth rate (b), death rate (d), immigration (i), and emigration (e)
• The natural rate of increase (r) is calculated as birth rate (b) - death rate (d) x 100
• Doubling time (td) is the time it takes for a population with a stable growth rate to double in size
• Immigration (i) refers to the migration of individuals into an area, while emigration (e) refers to the migration of individuals out of an area
• The growth rate of a local population is determined by (b - d) + (i - e), considering immigration and emigration
• Biotic potential indicates how many babies a species is capable of having, and it can change with conditions
• Population density is the number of individuals of a species per unit of area
• Carrying capacity (K) is the upper limit of the population in a given area, determined by biotic and abiotic factors
• Density-dependent controls include competition for resources, predation, and disease, which increase as population density in an area increases
• Density-independent controls like seasonal changes and natural disasters act on populations regardless of density
• Reproductive and survivorship curves categorize the survival rates of populations into Type I, Type II, and Type III
• Global population was 6.5 billion in 2008 and 7.2 billion today, with a rate of natural increase of 1.2%
• China has the largest population with 1.3 billion people, with a life expectancy of 67 years
• Key demographic indicators include replacement-level fertility, infant mortality, total fertility rate (TFR), and per capita income
• Total fertility rate (TFR) is the average number of children a woman will have in her reproductive years
• Industrialization affects population size through the demographic transition
• Comparing age structures can be done using age structure pyramids, with different shapes representing different nations
• Population Ecology or Demography study how populations change over time
• Factors that contribute to the natural rate of increase (r) of a population are birth (b) and death rates (d)
• Natural populations change in size in response to the relationships between births and deaths (r=b - d)
• For local populations like countries, immigration (i) and emigration (e) rates also need to be considered to predict growth rate (r=b - d + i - e)
• All species tend to over-produce, but populations don't continue to grow forever due to environmental resistance
• Environmental resistance factors include competition, predation, disease, and lack of resources
• Population growth can be limited by density-dependent factors like competition and disease, or density-independent factors like drought and fire
• Populations grow exponentially until they reach the carrying capacity of the environment, stabilizing at that size
• Stage 1 (Pre-Industrial): High birth and death rates, stable intrinsic growth due to natural checks like droughts and disease
• Stage 2 (Transitional/Developing): Death rates drop, birth rates stay stable, population grows rapidly due to technological advancements lowering death rates
• Stages 3 & 4 (Industrial and Post-Industrial): Countries must find ways to lower birth rates to move out of stage 2, leading to stabilized population growth
• As nations continue through stage 3, birth rates fall below death rates, entering stage 4 or Zero Population Growth where populations decline
• Highly developed economies focus on sustainability in energy use and resource consumption