Human Population Intro Notes

Population Ecology Studies the dynamics of species’ populations and how these populations interact with the environment Plays an important role in the development of the field of conservation, especially in predicting the long-term probability of a species persisting in a given habitat Increase Success Decrease Success High birthrate Low birthrate Few competitors Too many competitors Able to adapt Unable to adapt. Able to migrate Unable to migrate

Exponential, logistic, carrying capacity (part 1 of 3) Growth rate- the number of offspring an individual can produce in a given time period, minus the deaths of the individual or offspring during the same period. Intrinsic growth rate- under ideal conditions, with unlimited resources, the maximum potential for growth. J-shaped curve- when graphed the exponential growth model looks like this.

Exponential Growth Exponential growth occurs when the population size and its rate of growth both increase. It took over 70,000 years to reach 1 billion. 150 years to reach 3 billion. 25 years to reach 4 billion. 20 years to reach 5 billion 12 years to reach 6 billion. 11 years to reach 7 billion.

Year Growth Rate Doubling Time 1970 2.09 34 years 1980 1.82 38 years Another way of measuring growth is through doubling time, an estimate of how long it will take the population to double in size at its current rate of growth. Doubling time is calculated with this equation: 70 / (Current % Growth Rate) Year Growth Rate Doubling Time 1970 2.09 34 years 1980 1.82 38 years 1990 1.60 44 years 2000 1.26 56 years 2010 1.12 63 years

Exponential, logistic, carrying capacity (part 2 of 3) Logistic growth- when a population whose growth is initially exponential, but slows as the population approaches the carrying capacity. S-shaped curve- when graphed the logistic growth model produces an “S”.

Exponential, logistic, carrying capacity (part 3 of 3) Carrying capacity (K) Number of individuals that can be supported in a given area sustainably. Factors that keep the carrying capacity in balance are: food availability, space, oxygen content in aquatic ecosystems, nutrient levels in soil, and amount of sunlight.

Survivorship (part 1) R-strategy: Have many offspring Low parental care Short lived Tend to be small Mature rapidly species that have high reproductive rates Type III survivorship curve Population size limited by density independent limiting factors (climate, weather, natural disasters)

Survivorship (part 2) K strategy: species that reproduce later in life and with fewer offspring High parental care Long lived Tend to be larger Mature slowly Low reproduction rate Type I or II Population size limited by density dependent factors (intra-specific, competition, predation, parasitism, and migration)

HUMAN DEMOGRAPHY (bolded items should be written down) Demographics is the study of human populations. Includes comparing statistics such as births, deaths, gender, race, and economic status. Developing countries have populations that tend to be poorer, younger, and are growing much more rapidly. Developed countries are wealthy, old, and tend to have decreasing population sizes.

The Human Population Can Grow, Decline, or Remain Fairly Stable Population change = (births + immigration) – (deaths + emigration) Crude birth rate The number of live births/1000/year Crude death rate The number of deaths/1000/year

Several Factors Affect Death Rates Life expectancy - the average # of years an infant can expect to live Infant mortality rate: The infant mortality rate (IMR) is the number of deaths of infants under one year old, per 1,000 live births. High infant mortality rate indicates: Inadequate health care for poor women during pregnancy and their infants (poverty) Drug addiction among pregnant women High birth rate among teenagers

Migration The movement of individuals between areas can have a major impact on population change. Emigration is when people move out of an area. More likely to occur in developing countries. Immigration is when people move into an area. More likely to occur in developed countries.

Japan had a fertility rate of 1.39 in 2011. In some developed countries, immigration offsets or delays the normal population decline. The United States total fertility rate in 2011 was 1.89, below replacement level. The overall immigration was over 11 million. The population growth rate was 0.7%. Japan had a fertility rate of 1.39 in 2011. The overall immigration was just over 200,000. Their population growth rate is -0.2%.

Several Factors Affect Birth Rates and Fertility Rates Children as part of the labor force Cost of raising and educating children Availability of private and public pension Urbanization Educational and employment opportunities for women Average age of a woman at marriage Infant mortality rates Availability of legal abortions Availability of reliable birth control methods

Age Structure When studying the demographics of a single country, two of the most important factors to examine are gender and age distribution. These variables are graphed as population pyramids, and can provide valuable insight into a country.

What is the overall shape of the graph? Is there a dominant age group or groups? What proportion of the 0-4 age group survives into the elderly (60+) age groups? Are the male and female sides roughly equal?

Generalized Population Age Structure Diagrams (part 1) There are 3 major age groups in a population 1. Pre-reproductive 2. Reproductive 3. Post reproductive

Generalized Population Age Structure Diagrams (part 2) Pyramid shaped age structure Indicates the high population has a high birth rate And the majority of the population in reproductive age group

Generalized Population Age Structure Diagrams (part 3) A bell-shaped indicates that pre-reproductive and reproductive groups are nearly equal, with the post-reproductive group being the smallest due to mortality; this is characteristic of stable populations

Generalized Population Age Structure Diagrams (part 4) An urn shaped diagram indicates the post reproductive group is the largest and the pre-reproductive group is the smallest, a result of the birthrate falling below the death rate and is characteristic of declining populations

Demographic Transition (write bolded and draw picture on back of foldable)

Population Growth : Opposing Factors Pronatalist pressures increase the likeliness of individuals within a population to have more children. Source of pleasure, pride, comfort. Source of support for elderly parents. Aid in supporting family income. Counteracting high child mortality rates. Social status – importance of having a son. Most antinatalist pressures involve women. Higher education and personal freedom. More opportunities to earn a salary. Higher socioeconomic status.

Demographic Transition Model Countries will typically pass through a series of stages as they industrialize and transition from developing to developed countries. During the pre-industrial stage, food shortages, malnutrition, poor sanitation, and lack of access to modern medicine keep death rates high. All regions of the world were in this stage up until the industrial revolution.

Population size begins to increase exponentially. During the early transition stage, access to food and medicine improves, leading to a rapid drop in death rates. Birth rates remain high, as family size is tied to cultural norms and religious beliefs. Population size begins to increase exponentially.

The population continues to increase, but more slowly. During the late transition stage, efforts are made to reduce birth rate. Birth control and sex education gain greater acceptance. Women play a greater role in family planning. The population continues to increase, but more slowly.

The population stabilizes. During the industrial stage, birth rates have fallen back into balance with death rates. Total fertility rate is close to replacement level. The population stabilizes.

The population size decreases. During the post-industrial stage, birth rates continue to fall due to antinatalist pressures Total fertility rate is below replacement level. The population size decreases.

Four Stages of the Demographic Transition

FUTURE OF HUMAN POPULATIONS Most demographers believe the world population will stabilize sometime during the next century. Projections of maximum population size: Low 8 billion Medium 9.3 billion High 13 billion