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Population Dynamics

Population Dynamics . Unit 2 APES. Why study Human Population?. The World may or may be soon overpopulated. Environmental Problems of Overpopulation: Resource Depletion Environmental Degradation. Essential Questions.

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Population Dynamics

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  1. Population Dynamics Unit 2 APES

  2. Why study Human Population? • The World may or may be soon overpopulated. • Environmental Problems of Overpopulation: • Resource Depletion • Environmental Degradation

  3. Essential Questions • What is the history of human population growth, and how many people are likely to be here by 2050? • How is population size affected by birth, death, fertility, and migration rates? • How is population size affected by percentages of males and females at each level? • How can we slow population growth? • What success have India & China had in slowing population growth? • What are major impacts of human activities on the world’s natural ecosystems?

  4. Is the World Overpopulated? • World pop is projected to increase from 6.6 billion to 8.9 billion between 2006 & 2050. • The debate over interactions between population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science. • Much of the world’s population growth is occurring in developing countries like China & India.

  5. Is the World Overpopulated? • Some people argue that the planet has too many people. • Some feel that the world can support billions of more people due to technological advances. • There is a constant debate over the need to reduce population growth. • However, moral, religious, and personal freedoms must be considered.

  6. Brief History of Human Population Growth • Grew slowly at first but has grown rapidly recently because of the expansion of agriculture and industrial production (Industrial Revolution) AND lower death rates from improvements in hygiene and medicine. • In 2006, the population of developed countries grew exponentially at 0.1% per year, while, developing countries grew at 1.5% per year (15x faster)

  7. Where is the World Population Headed? • We do not know how long we can continue to increase the Earth’s capacity for human before the environment breaks down. • There are likely to be between 7.2-10.6 billion people of Earth by 2050. • 97% of the population growth will come from people in developing countries living in acute poverty (< $2 USD/day ~12 Yuan/day)

  8. UN Projections for Pop Growth • Projections based on high, medium, or low world average fertility rates (# of children/woman). • High 2.5 • Medium 2.0 • Low 1.5

  9. Opposite Views Of Population Growth & Issues • Poverty • Thomas Malthus Human Pops grow exponentially until disease or famine, or social conditions reduced fertility rates.

  10. Opposite Views Of Population Growth & Issues • Exploitation • Oppression • Poverty • Excess Population Growth Pop Growth results from poverty and social ills. Pop Growth would slow if all people were treated justly. • Karl Marx

  11. Population Dynamics ~ The Basics • Biotic Potential: reproductive rate of an organism if resources were unlimited & conditions were ideal. • For example the common housefly can lay 120 eggs in each generation (56 days). If nothing hurt the eggs or the flies, in 7 generations (1 year) there would be 5.6 trillion flies from 1 proud parent! • However, there are of course limiting factors. • Scarcity of resources, competition, predation, disease, accidents, etc.

  12. “J Curve”

  13. Environmental Resistance • Exponential growth can only with unlimited resources, but factors usually limit growth (environmental resistance). • Carrying Capacity (K): Number of organisms that an area can support without depleting resources

  14. Adapting to Environmental Resistance • Over time species may increase their carrying capacity by developing adaptations. • Some species maintain their carrying capacity by migrating to other areas. • So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for humans.

  15. Growth Patterns: • EXPONENTIALGROWTH: pop growth increases at a constant rate per unit of time. • 2-4-8-16-32-64-…. • LOGISITIC GROWTH: pop growth is slowed as it approached carry capacity due to scarcity of resources, etc.

  16. Logistic Growth “S Curve”

  17. Population Density • Number of organisms in a defined space • Density Dependent: growth rate depends on the population density. • Disease, stress, predation, etc. • Logistic Growth is density dependent • Density Independent: population control factors not dependent on population density. • Drought, fire, habitat destruction, weather

  18. Responding to Limits: Reproductive Strategies r-selected & K-selected species

  19. Survivorship Curves Late loss Constant loss Percentage surviving (log scale) Early loss Age

  20. Factors that Affect Population Growth • r = (B+I) – (D+E) • rate of growth • B = births • I = immigration • D = deaths • E = emigration

  21. Demographics • Vital statics about people such as • Births, • Deaths, • Immigration • Emigration • Where they live • Population size, • Etc.

  22. The Young, Poor, & Growing Countries • Asia, Africa, & Latin America • 80% of the world population, 90% of projected growth • Highest growth “hot spots” • Sub-Saharan Africa, Middle East • Economics, politics, religion, civil unrest, • High birth rates, low contraceptive use) • Highest growth rates • United Arab Emirates @ 6.8%

  23. The Older, Rich, Relatively Stable Countries • N. America, W. Europe, Japan, Australia, & New Zealand • Italy, Germany, Hungary & Japan have declining growth rates. • Average age = 40, Life expectancy = 90, women are choosing to not have children • Japan is currently around 127 million and expected to decrease to 100 million in 2050

  24. 1) Fertility/Birth Rates • Crude Birth Rate (B): number of births in a year per 1000 people • Total Fertility Rate (TFR): number of children born to an average woman in her reproductive life. • Replacement Level Fertility (RLF): number of children needed to replace the parents. • About 2.1 children in developed countries • Higher in other countries with a high infant mortality rate

  25. 1) Fertility/Birth Rates Cont. • Rates have declined in every region except for Africa • Thailand reduced their TFR from 7.0 in 1979 to 1.64 in 2009 • China went from a TFR 6.0 in 1970 to 1.8 in 1990 to 1.6 in 2009 due to the one-child policy • Macao has lowest TFR in the world with 0.9 • World Average TFR = 2.6

  26. Factors Affecting Fertility & Birth Rates • Cost of raising & educating the children • Availability of pensions • Urbanization • Education & employment opportunities • Infant deaths • Marriage age • Availability of contraception & abortion • Women’s Rights within a culture • Cultural beliefs, traditions, & cultural norms

  27. 2) Mortality (Death) Rates • Crude Death Rate: number of deaths per 1000 people in year • Less Developed countries, such as Africa, see death rates of 20+/1000. • Wealthier countries see about 10/1000 • Infant Mortality Rate: Number of child/infant deaths. • Natural Increase = crude birth rate – crude death rate

  28. Factors Affecting Mortality Rates • Increased food supplies and distribution. • Better nutrition • Medical & public health technology (immunizations/antibiotics) • Improved sanitation & personal hygiene • Safety of water supplies

  29. 2006

  30. 3) Immigration & Emigration • Immigration (I): people migrating into a population • Emigration (E): people migrating out of a population • Net Migration (I-E): Total number of people moving in and out of a population

  31. r = (B+I) – (D+E) • Total Growth rate (r): calculate using crude rates (per 1000) and divide by 10 = percentage • Zero Population Growth (ZPG): when B+I = D+E • Doubling time: amount of time it takes for a population to double • Rule of 70s: Divide 70 by annual natural increase equal the approximate doubling time

  32. r = (B+I) – (D+E) If a population of 10,000 experiences 100 births, 40 deaths, 10 immigrants and 30 emigrants in a year, what is the net annual percentage growth rate?

  33. Doubling Time • If a population of a country grows at a rate of 5% a year, the number of years required for the pop to double is what?

  34. The world’s 10 most populous countries in 2006 with projections in 2025.

  35. U.S. Trends • Nearly 2.9 million people added to the US in 2006. • 59% occurred because of births outnumbering deaths. • 41% came from illegal and legal immigration. • Sharp Rise in US birth rates during 1946-1964 called the Baby boom. • Economic success & Men returning home from war.

  36. US Trends • The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion.

  37. Case Study: Fertility and Birth Rates in the United States • In 2006, the total fertility rate in the United States was slightly > 2.0

  38. U.S. Trends Since 1820, the U.S. has admitted almost twice as many immigrants and refugees as all other countries combined.

  39. U.S. Trends • U.S. infant mortality is higher than it could be (ranked 46th world-wide) due to: • Inadequate pre- and post-natal care for poor. • Drug addiction. • High teenage birth rate.

  40. 4) Life Expectancy (LE) • Age that a newborn infant can be expected to live to (average age of death) • Most population growth is due to a decline in death rates b/c of longer life expectancy. • General Trends: • More developed countries have higher LE • Women tend to have higher LE than men • More money, longer life

  41. Implications of Longer Lives on Populations • Increased dependency ratio: • Number of non-working compared to working individuals in a population. • Countries, such as US & Japan, are seeing the number in the working force decline as the number of retiring individuals increases.

  42. Age Structure • Percentage of people in young, middle, and older age groups determines how fast populations grow or decline. • Generation time: time it takes for one generation to pass • The number of people younger than age 15 is the major factor determining a country’s population growth. • Changes in the distribution of a country’s age groups have long-lasting economic and social impacts.

  43. Histograms • Graphs that shows the different age classes of a population • Pre-reproductive age (14 and under) • Not mature enough to reproduce • Reproductive age (15-45) • Able to reproduce • Post-reproductive age (46 and older) • To old to reproduce • Broken down by age. You can see the birth rate, maturity rate and death rate of an entire population. Usually broken down by country

  44. Histograms • Populations with a large proportion of its people in the reproductive ages 1-14 have a large potential for rapid population growth.

  45. 32% of the people in developing countries were under 15 years old in 2006 versus only 17% in developed countries.

  46. Today, baby boomers make up nearly half of all adult Americans and dominate the populations demand for goods and services.

  47. Expansive/rapid growth • Birth rate exceeds the death rate. Population is getting larger. Pyramid shaped histogram. • Ex’s. Kenya, Nigeria and Saudi Arabia.

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