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Chapter 5

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  1. Chapter 5 The Human Population

  2. From Raven & Berg – Chapter 8 Population biology

  3. Principles of Population Ecology • The size of the human population is central to many environmental problems and their solutions • Important that we understand how populations increase or decrease • Population – a group of organisms of the same species that live in the same geographical area at the same time

  4. Population Ecology • Deals with the number of individuals of a particular species that are found in an area and how and why those numbers increase or decrease • Population ecologists try to determine the population processes that are common to all populations • Which we will apply to chapter 5 in our text book (Human Populations)

  5. Aspects of Population Ecology • Study how a population competes for food or other resources • How predation, disease, and other environmental pressures affect the population • Reproductive success or failure

  6. Maximum Population Growth • The maximum rate at which a population could increase under ideal conditions is known as its biotic potential, or intrinsic rate of increase. • Different organisms have different biotic potentials

  7. Factors That Affect Biotic Potential • Age at which reproduction begins • Reproducing earlier in life has the greatest effect on biotic potential • Duration of when organism is capable of reproduction • Number of reproductive periods per lifetime • Number of offspring produced during each period of reproduction • Factors are called life history characteristics

  8. Reproductive Strategies • r – selected species • Have traits that contribute to a high population growth rate • (r designates growth rate) • Small body size, early maturity, short life span, large broods, and little or no parental care are typical of many r strategists • Usually opportunists, found in variable, temporary, or unpredictable environments • Probability of long term survival is low

  9. Reproductive Strategies • K – selected traits • Traits maximize the chance of surviving in an environment where the number of individuals (N) is near the carrying capacity (K) of the environment. • Do not produce large numbers of offspring • Have long life spans with slow development • Late reproducing • Large body size • Typically invest in parental care of their youngsters

  10. Survivorship • Ecologists construct life tables for plants and animals that show the likelihood of survival for individuals at different times during their lives. • Survivorship is the probability that a given individual in a population will survive to a particular age

  11. Type III Survivorship • The probability of death is greatest early in life • Those individuals that avoid death, subsequently have a high probability of survival • Characteristic of many fish species and oysters

  12. Type III Survivorship

  13. Type II Survivorship • Intermediate between types I and III. • Probability of death is likely across all age groups • Results in a linear decline in survivorship • This results from the essentially random events that cause death with little age bias • This curve is rare, some lizards have a type II survivorship

  14. Type II Survivorship

  15. Type I Survivorship • Exemplified by humans and elephants • The young (pre-reproductive) and those at reproductive age have a high probability of living • Probability of survival decreases more rapidly with increasing age • Deaths are concentrated later in life.

  16. 5.1 Human population expansion and its causes

  17. Warm-Up • Define chapter 5 vocabulary terms. Vocab quiz Wednesday • Fertility • Replacement level fertility • Demography • Population profile • Graying • Demographic Transition • Phase I, II, III, IV • Crude death rate • Crude birth rate • Doubling time • Rule of 70

  18. History • Considering the thousands of years of human history, the recent rapid expansion of the global population is a unique event • From the dawn of human history until the beginning of the 1800s population increased slowly • It was roughly 1830 before the world population reached 1 billion

  19. History • By 1930, the population had doubled to 2 billion • 1975 – 4 billion • 1987 – 5 billion • 1999 – 6 billion • Currently growing at the rate of 76 million people added a year • Based on current information, medium projection predicts the world will pass 7 billion in 2012 • 8 billion – 2024 • 9 billion - 2047

  20. Reasons for Patterns of Growth • Flow/fluctuating growth wad due to the prevalence of diseases • High reproductive rates were balanced with a high infant mortality rate • High birth rate and death rate causes slow population growth

  21. Breakthroughs • Late 1800s • Louis Pasteur discovered diseases were caused by infectious agents • Organisms transmitted by food, insects, water, rodents • Vaccinations were developed • Cities and towns began treating driving water • Discovery of penicillin in the 1930s • Improvements in nutrition

  22. Declines • 1960s – growth rate peaked at 2.1% increase a year • Declines result of decline in total fertility rates • Average number of babies born to a woman over her lifetime • In 1960s fertility rate was an average of 5.0 children per woman • Present value 2.7 children per woman

  23. UN Population Projections • Demonstrate role played by fertility assumptions • Constant projection – 2.6 children • Medium projection – assumes decline in fertility rate in developing countries (2.02/woman) • High projection – assumes fertility rates ½ child greater than the Medium projection • Low projection – assumes fertility rates ½ child less than Medium projection

  24. 5.2 Different Worlds

  25. Rich Nations, Poor Nations • The World Bank, and arm of the United Nations, divides the countries of the world into three main economic categories according to average per capita gross national income

  26. High Income, Highly Developed, Industrialized Countries • 971 million in 2003 • Includes the U.S., Canada, Japan, Korea, Australia, New Zealand, the countries of western Europe and Scandinavia, Singapore, Taiwan, Israel, and several Arab states • 2003 gross national income per capita • $9,386 and above; average of $28,550

  27. Middle Income, moderately developed countries • 3 billion in 2003 • Countries of Latin America, northern and southern Africa, China, Indonesia and other southeastern Asian countries, many Arab states, eastern Europe and countries of the former U.S.S.R • 2003 gross national income per capita ranges from $755 to $9,385; average of $1,920

  28. Low-Income, Developing Countries • 2.3 billion • Comprises the countries of eastern, western, and central Africa, India, and other countries of Asia, and a few former Soviet republics • 2003 gross national income per capita is less than $766 • Average of $450

  29. Disparities • High income countries make up 15% of world’s population • Control 80% of the worlds wealth • (calculated on the basis of gross national income) • Low income countries make up 37% of the world’s population • Control only 3% of the worlds wealth • Amounts to a difference in per capita income of 63:1!

  30. Human Development Index • United Nations Development Program (UNDP) • Measures general well-being based on more info about literacy, and living standards • Makes a more direct measurement of poverty in both LDC and MDC

  31. Dimensions of the Human Poverty Index Based on information about life expectancy, literacy, and living standards

  32. Population Growth In Rich and Poor Nations • More than 98% of the world population growth is occurring in the developing countries • 2006 growth rate developed countries – 0.1% • Add less than 1 million to the worlds population in a year • 2006 growth rate in developing countries – 1.5% • Adding 75 million in a year

  33. Fertility • Population growth occurs when births outnumber deaths • Total fertility rate • average number of children each woman in a population has over her lifetime • Replacement level fertility • Fertility rate that will just replace the population of the parents • 2.1 in developed countries, higher in developing countries which have higher infant/childhood mortality rates

  34. Population Increase in Developed and Developing Countries Because of higher birthrates, developing countries represent a larger and larger share of the world’s population

  35. Different Population, Different Problems • Ecologists Paul Ehrlich and John Holdren proposed a formula to account for the human factors that contribute to environmental deterioration and the depletion of resources • Human pressure on the environment was product of three factors • Population, affluence, technology

  36. IPAT formula • I = P * A * T • Environmental Impact (I) is proportional to population (P) multiplied by affluence and consumption patterns (A), and multiplied by the level of technology of the society (T)

  37. Demand vs. Need • Most environmental issues are a result of the high consumption associated with affluent lifestyles in developed countries • U.S – 5% of worlds population, 24% of global emissions of CO2 • Developing countries needs include economic growth, more employment, wise leaders, effective public polices, fair treatment by other nations, technological and financial help

  38. Stewardship • Developed countries must address issues to achieve sustainability • IPAT formula might be modified to • I = P * A * T S S stands for stewardly concern and practice

  39. 5.3 Consequences of population growth and affluence

  40. Developing Countries • Prior to industrial revolution most human population survived through subsistence agriculture • Families lived on the land, raised livestock,and produced enough crops for their own consumption

  41. Rural Populations • 70% of the world’s poor live in rural areas • Most are engaged in small-scale agriculture • Environmental impacts on population growth of this sect of the population

  42. 1. Land Reform • Reform system of land ownership • Collectivization and ownership by the wealthy are two patterns of agriculture land ownership that have kept rural peoples in poverty

  43. 2. Intensifying Cultivation • Introduction of more highly productive varieties of basic food grains • Beneficial effect in supporting growing population • Consequences • Working the land harder, increasing intensity of grazing • Deterioration of soil, decreased productivity, erosion, desertification

  44. 3. – Opening New Lands for Agriculture • Means converting natural ecosystems to agricultural production • Losing the goods and services those ecosystems were contributing • Most of the time the ecosystem converted isn’t suited for agriculture and requires large inputs of water and fertilizer