Presentation on theme: "Environmental Science Ch.9 Guided Notes: Human Population"— Presentation transcript:
1 Environmental Science Ch.9 Guided Notes: Human Population Introduction Paul Ehrlich published The Population Bomb in 1968.
2 IntroductionIt created a lot of controversy. One of the premises of the book is that any environmental issue is really just a human overpopulation issue.Ehrlich believed that:Every environmental problem is directly related to there being too many people on earth.The way to help the environment is to control over population
3 Questions to Ponder: Do we have a human population problem? If so, is overpopulation at the root of all environmental problems?Can the population be controlled?What strategies exist to keep population in check, and will these measures help the environment?
4 Section 1: Studying Human Populations Demography is the study of populations but most often refers to the study of human populations.Demographers studythe historical size and make up of populations of countries in order to make comparisons and predictions.Properties that affect population growth such as economics and social structure
5 Demographers group countries into 2 categories: Developed countries have higher average incomes, slower population growth and diverse industrial economiesDeveloping countries have lower average incomes, simple and agriculture-based economies, and rapid population growth
6 How Does a Species Population Change? Birth ( add more individuals)Death (remove individuals)Migration (immigration/emigration)
7 Assuming no migration If Births > Deaths, the population grows If Births < Deaths, the population declinesOver the course of many years, population changes oscillate around a dynamic equilibrium.
8 The Human Population Over Time After growing slowly for thousands of years, the human population grew rapidly in the 1800s. The increase was exponential (J-curve) See Fig. 1 pg.235This is the Standard Growth Curve.
9 Most hunter/gatherer populations existed before 10 KYA. These populations were very small and had very little population growth.Death rates and birth rates were both very highCatastrophic population crashes were also possible
10 better living conditions The Agricultural Revolution resulted in a greater rate of population gowthbetter living conditionsIncrease in birth rate due to the abundance of foodOccurred through the development of cultivation of animals and plants.Occurred in many regions of the world.
11 The Industrial Revolution resulted in Greater rise in populationDecreased death rateIncreased birth rateBetter health care and medicineBetter nutrition and sanitation practicesIncrease in food productionTechnological advances in just about every field increasedDemand for labor may have contributed to the increase in the population.
12 The world population reached 1 billion for the first time in 1830 The world population reached 2 billion in 1930., only 100 years since 1830!
13 Exponential Growth Curve The population doubles with each generation.Growth is very slow at first, but as population increases over time, the growth rate becomes enormous.Carrying capacity – the maximum number of individuals that the environment can support.
15 Forecasting Population Size ( Factors that affect population growth) Age structure – the distribution of ages in a specific population at a certain timeIf a population has more young people than old, the population size will likely increase as the young grown and reproduce
16 If a population has more older people than young, the population will likely decrease Population pyramid – a double-sided bar graph that shows age distribution of a population.
18 SurvivorshipThe percentage of members of a group that are likely to survive at any given age.To predict survivorship, demographers studies a group of people born at the same time and notes when each person dies.
19 Type I survivorship – wealthy countries such as Japan and Germany Type I survivorship – wealthy countries such as Japan and Germany. Most people live to be very oldType II survivorship – populations have a similar death rate at all ages.Type III survivorship is the pattern in very poor human populations in which many children die.
20 Fertility RateThe number of babies born each year per 1,000 women in a population.Total fertility rate – the average number of children a woman gives birth to in her lifetimeReplacement level – the average number of children each parent must have in order to replace themselves in the population.
21 Migration The movement of individuals between areas Immigration – movement into an areaEmigration – movement out of an area.The populations of many developed countries might be decreasing if not for immigration.
22 Declining Death RatesMore people now have access to clean water, adequate food and safe sewage disposal.Discovery of vaccines in the 20th century contributed to declining death rates (polio, small pox, diptheria)
23 Life ExpectancyThe average number of years members of a population are likely to live.Most affected by infant mortality – the death rate of infants less than a year old.By 2000, the rate of infant mortality was less than one-third the rate in 1900.Infant health is most affected by the parents’ access to education, food, fuel, and clean water.
24 Demographic Transition A model that describes how economic and social changes affect population growth rates.Stage 1 – society is in pre-industrial condition.Birth rate and death rates are at high levelPopulation stable.The world was in this stage until 1700’s
25 Stage 2 – population explosion occurs. Death rates decline as hygien, nutrition and education improve.Population can double in less than 30 years.Stage 3 – population growth slows because the birth rate decreases.population stabilizesStage 4 – birth rate drops below replacement level, so the size of the population begins to decrease.Takes from one to three generations for the demographic transition to occur in most developed countries.
26 Women and FertilityThe factors most clearly related to a decline in birth rates are increasing education and economic independence for women.Large families are valuable in communities in which children work or take care of older family members.
27 Section 2 : Changing Population Trends Populations that have high rates of growth create environmental problemsResources are used at an increased rate and can overwhelm the infrastructure of a community
29 Symptoms of an Overwhelming Population Suburban sprawlOvercrowded schoolsPolluted riversBarren landInadequate housing
30 Problems of Overcrowding Shortage of fuelwood – wood is the main fuel source for boiling water and cooking foodUnsafe water – the main water supply used for washing, drinking AND sewage. Water systems cannot be expanded fast enough to keep up with growthShortage of arable land
31 Managing Population Growth China, Thailand, India use public advertising, family planning programs, economic incentives, legal punishment, forced abortion.1994 – The United Nations held the International Conference on Population and Development(ICPD) and set goals to stabilize population growth through investments in development, and improving women’s status.
32 Growth is Slowing 7 billion!!! Current population Fertility rates decliningMost countries will have replacement level fertility rates by 2050, if so, world population growth would eventually stop
33 United States Facts Population: 313,232,044 (July 2011) Age Structure: 0-14 years: 20.1%15-64 years: 66.8%65 years and over: 13.1%Birth Rate: births/1,000 populationPer couple: 2.1 in 2005 (Europe 1.3)