Presentation on theme: "Environmental Science"— Presentation transcript:
1 Environmental Science Chapter 9 Lecture NotesThe Human PopulationIntroduction to Human Population Growth (11")
2 Chapter 9 Targets1. I can define demography and describe the 2 general categories of population growth they study.2. I can describe how the size and growth rate of the human population has changed in the last 200 years.3. I can make predictions about population trends based on age structure.4. I can describe how survivorship, fertility, migration, death rate and life expectancy affect populations.5. I can describe the four stages of the demographic transition.6. I can name the 2 main factors affecting birth rates.
3 Studying Human Populations Demography: study of HUMAN populationsCountries based on 2 population trends:Developed and Developing countries.Developed countries have: average incomes industrial economies social support systems population growthDeveloping countries have: average incomessimple and agriculture-based economics population growthT1
4 The Human Population Over Time Human population underwent exponential growth in the 1800s. WHY?Better food production and hygiene came with the industrial and scientific revolutions
5 Age StructureT3Age structure/Population Pyramid: classifies a population into groups by age agehelps demographers make predictionsCountries with high growth rates usually have more young than old peopleCountries with slow growth or no growth usually have an even distribution of ages in the populationEthiopaRussiaUnited States
6 SurvivorshipT4Survivorship: % of newborns in population expected to survive to a given ageused as another way to predict population trends(see video)Which survivorship curve would belong to humans? Frogs? Robins?
8 Fertility RatesT4Fertility rate: number of births (per year) per 1,000 women of childbearing age (usually 15 to 44)Replacement level: average number of children each parent must have in order to “replace” themselvesThis number is slightly more than 2 because not all children born will survive and reproduce
9 MigrationT4Migration: movement of individuals or populations from one location to anotherImmigration vs. EmigrationPopulations of many developed countries might be decreasing if not for immigration
10 Declining Death Rates Dramatic in human population in last 200 years Happened because death rates declined faster than birth ratesDeath rates declined mainly because more people now have access to enough food, clean water, and safe sewage disposalDiscovery of vaccines in 20th century also contributed to declining death rates
11 Life ExpectancyT4Life expectancy: average length of time an individual is expected to liveLife expectancy is most affected by infant mortality, the death rate of infants less than a year old
12 The Demographic Transition Demographic transition: general pattern of demographic change from high birth/death rates to low birth/death ratesSeen during history of more-developed countriesStages of Demographic Transition Video (1")
13 Stages of Transition First stage: society is preindustrial Birth/death rates are high and population size is stableSecond stage: population explosion occursDeath rates decline as hygiene, nutrition, and education improve. Birth rates remain high, so population grows very fast.Third stage: population growth slows because birth rate decreasesBirth rate = death rate, population size stabilizesFourth stage: birth rate drops below replacement level, population begins to decrease
14 Women and FertilityT6The factors most clearly related to a decline in birth rates are increasing education and economic independence for women
15 Chapter 9 Targets7. I can describe three problems caused by rapid human population growth.8. I can compare population growth problems in more-developed countries and less developed countries.9. I can analyze strategies countries may use to reduce their population growth.10. I can describe worldwide population projections into the next century.
16 Problems of Rapid Growth Rapidly growing population uses resources faster than environment can renew themLiving standards drop when wood is removed from local forests faster than it can grow back, or when wastes overwhelm local water sourcesSymptoms of overwhelming populations include polluted rivers, barren land, inadequate housing, and overcrowded schools
17 A Demographically Diverse World T8Least developed countries: identified by U.N. as showing fewest signs of improving income, human resources, and economic diversityPopulations are still growing rapidly in less developed countries, with most of the world’s population now in Asia
18 Managing Development and Population Growth Less developed countries face continued population growth that will prevent them from developing into world economic leadersCountries such as China, Thailand, and India have created campaigns to reduce fertility rates of their citizensThese campaigns include public advertising, family planning programs, economic incentives, or legal punishment
19 Managing Development and Population Growth In 1994, United Nations held International Conference on Population and Development (ICPD)Involved debates about relationships between population, development, and the environment
20 Managing Development and Population With these goals, worldwide fertility rates are dropping as shown below (see assignment)
21 Projections to 2050T10Looking at the graph below, most demographers predict the medium growth rate, and a world population of 9.2 billion in 2050Current population is at 7 billionPopulation Clock