Population By: Rebecca Marty Formula for Population Actual rate of population change can be determine by an Formula: Actual Growth rate (%) = birth rate- death rate divided by 10 Ex. The United states had a birth rate of 14.6 live births per 1,000 population in one year. The death rate in that year for the United States was 8.3 deaths per 1,000 population. Calculate the Population Growth rate (%) for the United States in that year. Distribution In 1800, the vast majority of the world’s population (65 %) resided in Asia and Europe. Between 2000 and 2030, most of the growth will occur at the less- developed countries in Africa, Asia, and Latin America whose growth rates are much higher than those in moredeveloped countries. The more- developed countries in Europe and North America will have growth rates less than 1% . Some countries such as Russia, Germany, Italy, and Japan will even experience negative growth rates. Fertility Rates Replacement level fertility (RLF) is the level of fertility at which has only enough children to replace themselves, or about 2 children per couple. It takes RLF of 2.1 to replace each generation since some children will die before they grow up to have their own two children. RLF rates are lower in moderately developed countries (MDC) and higher in less-developed countries (LDC) due to higher infant mortality rates in LDC. The total fertility rate (TFR) is the average number of children that each woman will have during her lifetime. Cont. Fertility Rates The world’s population is still growing quickly. This growth is due to nations with above-replacement TFRs and a population momentum caused by large numbers of younger females who have as yet not had children. Declines in fertility rates can be attributed to several factors. Urbanization results in a higher cost of living. Urbanization reduces the need for extra children to work on farms. There is a greater personal acceptance and government encouragement of contraception and abortion. The numbers of females in the workforce and female educational opportunities are increasing. More individuals desire to increase their standard living by having less children. The two main effects of TFRs less than 2.1 without additions through immigration are population decline and population aging. Growth Models There are Two reproductive strategies: r-selected species: have adaptations that permit them to rapidly increasing their numbers and they tend to be below their carry capacity for long periods- but have potential to overshoot. K-selected species: have adaptations that permit them to live in a state of equilibrium and they are close to their carrying capacity. Type I- K-selected species that have high survival rates throughout most of their lifespan. As they approach old age, they die in large numbers Type II- relatively constant decline in survivorship throughout their lifespan Type III- r-selected species experience low survivorship early in life; few reach adulthood Exponential Growth “ J- Curve”- is growth at a constant rate Logistic Growth “ S- Curve” this reaches its carrying capacity Surviorship Growth- is a graph showing the number or proportion of individuals surviving at each age for a given species or group Exponential, Logistic, and Survivorship Models Demographic Transition Demographic Transition- refers to the transition from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system. Or is a model that describes population change over time. There are 4 stages: Stage 1: Pre modern- is associated with pre modern times, and is characterized by a balance between birth rates and death rates. Stage 2: Urbanizing/Industrializing- sees a rise in population caused by a decline in the death rate while birth rate remains high, or perhaps even rises slightly. Stage 3: Mature Industrial – moves the population towards stability through a decline in one birth rate. Stage 4: Post Industrial – is characterized by stability in this stage the population age structure has become older. Age- Structure Diagrams A good indicator of future trends in population growth is furnished by age-structure diagrams. Age structure diagrams are determined by birth rate, generation time, death rate, and sex ratios. When the Base is large ( greater number of individuals in the population), there is a potential for an increase in the population as these younger individuals mature and have children of their own (population momentum). When the top of the pyramid is larger, it indicates a large segment of the population is past their reproductive years and indicates a future slowdown in population growth. Age structure Diagrams Helpful Website Links http://www.marathon.uwc.edu/geograp hy/demotrans/demtran.htm http://www.geography.learnontheinterne t.co.uk/topics/popn1.html http://en.wikipedia.org/wiki/Population http://en.wikipedia.org/wiki/Survivorship_c urve Video link http://www.gamequarium.org/cgi- bin/search/linfo.cgi?id=16214 http://www.gamequarium.org/cgi- bin/search/linfo.cgi?id=16214 Questions 1. 2. 3. 4. 5. 6. What is the population growth rate for the United States? ( Look at Formula and example at beginning) In your own words what does Demographic Transition mean? And List and explain the 4 stages? What does Replacement Fertility and Total Fertility Rate mean? What are the two main Effects of TFRs? Explain what the Age- Structure Diagram shows. The Two reproductive strategies are? And what do they mean? What are the Three Growth Models and in your own words explain what they mean? List the types and if its k- selected or r-selected?