1. Population Dynamics

2. Population Dynamics
Warm Up: Identify and describe three negative consequences of the practice of factory farming of chicken, cows, and pigs. Give one social and one economic advantage.

3. Populations
Organisms do not generally live alone. A population is a group of organisms from the same species occupying in the same geographical area.
This area may be difficult to define because:
A population may comprise widely dispersed individuals which come together only infrequently, e.g. for mating.
Populations may fluctuate considerably over time.
Migrating wildebeest population
Tiger populations comprise widely separated individuals

4. Features of Populations
Populations are dynamic and exhibit attributes that are not shown by the individuals themselves.
These attributes can be measured or calculated and include:
Population size: the total number of organisms in the population.
Population density: the number of organisms per unit area.
Population distribution: the location of individuals within a specific area.

5. Features of Populations
Population composition provides information relevant to the dynamics of the population, i.e. whether the population is increasing or declining.
Information on population composition (or structure) includes:
Sex ratios: the number of organisms of each sex.
Fecundity (fertility): the reproductive capacity of the females.
Age structure: the number of organisms of different ages.

6. Population size is influenced by births…
Population Dynamics
The study of changes in the size and composition of populations, and the factors influencing these changes, is population dynamics.
Key factors for study include:
Population growth rate: the change in the total population size per unit time.
Natality (birth rate): the number of individuals born per unit time.
Mortality (death rate): the number of individuals dying per unit time.
Migration: the number moving into or out of the population.
Population size is influenced by births…
…and deaths

7. Migrating species may group together to form large mobile populations
Migration
Migration is the movement of organisms into (immigration) and out of (emigration) a population. It affects population attributes such as age and sex structure, as well as the dynamics of a population.
Populations lose individuals through deaths and emigration.
Populations gain individuals through births and immigration.
Net Migration = Immigration - Emigration
Wildebeest - land based migration
Canada geese - aerial migration
Migrating species may group together to form large mobile populations

8. Population Density
The number of individuals per unit area (for terrestrial organisms) or volume (for aquatic organisms) is termed the population density.
At low population densities, individuals are spaced well apart. Examples: territorial, solitary mammalian species such as tigers and plant species in marginal environments.
At high population densities, individuals are crowded together. Examples: colonial animals, such as rabbits, corals, and termites.
Low density populations
High density populations

9. Population Distribution
A crude measure of population density tells us nothing about the spatial distribution of individuals in the habitat.
The population distribution describes the location of individuals within an area.
Distribution patterns are determined by the habitat patchiness (distribution of resources) and features of the organisms themselves, such as territoriality in animals or autotoxicity in plants.
Individuals in a population may be distributed randomly, uniformly, or in clumps.
Clumped distribution in termites
More uniform distribution in cacti

10. Spider populations appear to show a random distribution
A population’s distribution is considered random if the position of each individual is independent of the others.
Random distributions are not common; they can occur only where:
The environment is uniform and resources are equally available throughout the year.
There are no interactions between individuals or interactions produce no patterns of avoidance or attraction.
Random distributions are seen in some invertebrate populations, e.g. spiders and clams, and some trees.
Spider populations appear to show a random distribution

11. Saguaro cacti compete for moisture and show a uniform distribution
Uniform or regular distribution patterns occur where individuals are more evenly spaced than would occur by chance.
Regular patterns of distribution result from intraspecific competition amongst members of a population:
Territoriality in a relatively homogeneous environment.
Competition for root and crown space in forest trees or moisture in desert and savanna plants.
Autotoxicity: chemical inhibition of plant seedlings of the same species.
Saguaro cacti compete for moisture and show a uniform distribution

12. Sociality leads to clumped distribution
Clumped distributions are the most common in nature; individuals are clustered together in groups.
Population clusters may occur around a a resource such as food or shelter.
Clumped distributions result from the responses of plants and animals to:
Habitat differences
Daily and seasonal changes in weather and environment
Reproductive patterns
Social behavior
Sociality leads to clumped distribution

13. Density Dependent Factors
Density dependent factors exert a greater effect on population growth at higher population densities. At high densities, individuals:
Compete more for resources.
Are more easily located by predators and parasites.
Are more vulnerable to infection and disease.
Density dependent factors are biotic factors such as food supply, disease, parasite infestation, competition, and predation.
Competition increases in crowded populations
The intrinsic rate of increase (r) is the rate at which a population would grow if it had unlimited resources. Carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat.
Parasites can spread rapidly through dense populations

14. Species Interactions
No organism exists in isolation. Each participates in interactions with other organisms and with the abiotic components of the environment.
Species interactions may involve only occasional or indirect contact (predation or competition) or they may involve a close association between species. Symbiosis is a term that encompasses a variety of such close associations, including parasitism (a form of exploitation), mutualism, and commensalism.
Canopy tree with symbionts attached
Oxpecker birds on buffalo

15. Parasitism
Many animals have representatives that have adopted a parasitic lifestyle.
Parasites occur more commonly in some species than in others. Insects, some annelids, and flatworms have many parasitic representatives.
Parasites live in or on a host organism. The host is always harmed by the presence of the parasite, but it is not usually killed. Both parasite and host show adaptations to the relationship.
Parasites may live externally on a host as ecto, or within the host’s body as endoparasites.
Tick ectoparasite on bird wing
Many mammals use dust bathing to rid themselves of external parasites

16. Mosquito vector for Dengue fever (Aedes albopictus)
Ectoparasites
Ectoparasites, such as ticks, mites, lice, bed bugs, and fleas, live attached to the outside of the host, where they suck body fluids, cause irritation, and may act as vectors for pathogens or disease-causing agents.
Insect vectors include human lice, rat fleas, mosquitoes and tsetse flies.
Bed bug (Cimex lectularis)
Human flea (Pulex irritans)
Head louse (Pediculus humanus)
Mosquito vector for Dengue fever (Aedes albopictus)

17. Endoparasites
In many endoparasites, a primary host (in which the parasite becomes sexually mature) and one or more intermediate hosts (which usually house larval stages) are required to complete the life cycle.
Endoparasitic species such as the pork tapeworm, Taenia solium, are highly specialized to exploit the resources of the host.
Adaptations, such as specialized mouthparts and lack of a digestive tract, enable them to spend their life inside the intestines of their vertebrate hosts.
Taenia scolex (head region)
Taenia proglottid (reproductive segment)
Horse gut nematode
Sheep liver fluke

18. Plant Parasites
A great diversity of plant parasites exist. Some depend only partly on their host plant for nutrition; they are photosynthetic but utilize the host’s nutrients, e.g. mistletoe.
Others are entirely parasitic and are unable to photosynthesize, e.g. cancer root (Conopholis americana) dodder, and wood rose (Dactylanthus taylorii).
Cancer root (top) and wood rose are holoparasitic and dependent entirely on the host plant.
Mistletoe Phoradendren spp. are hemiparasites; photosynthesizing but lack their own roots and rob their host plant of water and nutrients.

19. Mutualistic Relationships
In mutualistic relationships both species benefit. This occur between some birds (such as oxpeckers) and large herbivores (such as zebra, Cape buffalo, and rhinoceros). The herbivore is cleaned of parasites and the oxpecker gains access to food.
Lichens show an obligate mutualism between a fungus and either a green algae or a cynobacterium. The fungus obtains organic carbon from the algae. The algae obtains water and nutrient salts from the fungus.
Cape buffalo and oxpecker birds
Lichen: an obligate mutualism

20. Commensal Relationships
In commensal relationships, one party (the commensal) benefits, while the host is unaffected.
Epiphytes (perching plants) gain access to a better position in the forest canopy, with more light for photosynthesis, but do no harm to the host tree.
Commensal anemone shrimps (Periclimenes spp.) live within the tentacles of host sea anemones. The shrimp gains protection from predators, but the anemone is neither harmed nor benefitted.

21. Exploitation
Exploitation describes relationships where one species benefits at the expense of another. It includes several familiar interactions:
Predation: Predator kills the prey outright, e.g. lions hunting zebra.
Herbivory: The herbivore feeds on, but usually does not kill, the plant, e.g. zebra grazing on grass.
Parasitism: The parasite does not usually kill its host, e.g. ticks feeding on the blood of a zebra.

22. Types of Interaction

23. Density Independent Factors
The effect of density independent factors on a population’s growth is not dependent on that population’s density:
Physical (or abiotic) factors
temperature
precipitation
humidity
acidity
salinity etc.
Catastrophic events
floods and tsunamis
fire
drought
earthquake and eruption
Factors that are not a part of the growing population. These factors are beyond the control of the organism and are usually result of the environment.

24. (Births – Deaths) + (Immigration – Emigration)
Population Growth
Population growth depends on the number of individuals added to the population from births and immigration, minus the number lost through deaths and emigration.
This can be expressed as a formula:
Net migration is the difference between immigration and emigration.
Population growth =
(Births – Deaths) + (Immigration – Emigration)
(B)
(D)
(I)
(E)

25. Calculating Population Change
Births, deaths, and net migrations determine the numbers of individuals in a population
Births (B)
Immigration (I)
Emigration (E)
Deaths (D)

26. Rates of Population Change
Ecologists usually measure the rate of population change. These rates are influenced by environmental factors and by the characteristics of the organisms themselves.
Rates are expressed as:
Numbers per unit time, e.g live births per year
Per capita rate number per head of population.
Crude rate per persons e.g. 122 live births per individuals (12.2%)
Many invertebrate populations increase rapidly in the right conditions
Large mammalian carnivores have a lower innate capacity for increase

27. Colonizing Population Population numbers (N)
Exponential Growth
Populations becoming established in a new area for the first time are often termed colonizing populations.
They may undergo a rapid exponential (logarithmic) increase in numbers to produce a J-shaped growth curve.
In natural populations, population growth rarely continues to increase at an exponential rate.
Factors in the environment, such as available food or space, act to slow population growth.
Colonizing Population
Here the number being added to the population per unit time is large.
Exponential (J) curve Exponential growth is sustained only when there are no constraints from the environment.
Population numbers (N)
For example the common housefly can lay 120 eggs in each generation. If nothing hurt the eggs or the flies, in 7 generations there would be 6,182,442,727,320 flies.
Here, the number being added to the population per unit time is small.
Lag phase
Time

28. Logistic Growth Model
As a population grows, its increase will slow, and it will stabilize at a level that can supported by the environment.
This type of sigmoidal growth (S) produces the logistic growth curve.
Established Population
The population encounters resistance to exponential growth as it begins to fill up the environment. This is called environmental resistance.
Carrying capacity (K)
The maximum population density that can be supported by the environment on a long term basis.
Environmental resistance increases as the population overshoots K.
Logistic (S) curve
As the population grows, the rate of population increase slows, reaching an equilibrium level around the carrying capacity.
Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off. As a population levels off, it often fluctuates slightly above and below the carrying capacity. The intrinsic rate of increase (r) is the rate at which a population would grow if it had unlimited resources. Carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat.
Population numbers (N)
Environmental resistance decreases as the population falls below K.
The population tends to fluctuate around an 'equilibrium level'. The fluctuations are caused by variations in the birth rate and death rate as a result of the population density exceeding of falling below carrying capacity.
In the early phase, growth is exponential (or nearly so)
Lag phase
Time

29. Life Tables
Numerical data collected during a population study can be presented as a table of figures called a life table.
Life tables provide a summary of mortality for a population. The basic data are the number of individuals surviving to each age interval. This gives the ages at which most mortality occurs in a population.
Life table for a population of the barnacle Balanus
Age (yr)
No. alive at the start of the age interval
Proportion of original no. surviving at the start of the age interval
No. dying during the age interval
Mortality (d)
142
1.000 80
0.563 1 62
0.437 28
0.452 2 34
0.239 14
0.412 3 20
0.141 5
0.250 4 15
0.106
0.267 11
0.078
0.454 6
0.042
0.667 7
0.014
0.000 8 9
0.0 –

30. Number of survivors (log scale)
Survivorship Curves
The age structure of a population can represented with a survivorship curve. Survivorship curves use a semi-log plot of the number of individuals surviving per 1000 in the population, against age.
Because they are standardized (as number of survivors per 1000), species with different life expectancies can be easily compared.
The shape of the curve reflects where heaviest mortality occurs:
Type I: late loss
large mammals
Type II: constant loss
small mammals, songbirds
Number of survivors (log scale)
Type III: early loss
oysters, barnacles
Relative age

31. Type I Survivorship Curves
Species with Type I or late loss survivorship curves show the heaviest mortality late in life. Mortality is very low in the juvenile years and throughout most of adult life.
Late loss curves are typical of species that produce few young and care for them until they reach reproductive age.
Such species are sometimes called K- selected species and include elephants, humans, and other large mammals.
Mortality is very low in early life
Mortality increases rapidly in old age

32. Type II Survivorship Curves
Species with Type II or constant loss survivorship curves show a relatively constant mortality at all life stages.
Constant loss curves are typical of species with intermediate reproductive strategies. Populations face loss from predation and starvation throughout life.
Examples include some many types of songbirds, some annual plants, some lizards, and many small mammals.
Constant mortality.
No one age class is any more susceptible than any other.

33. Type III Survivorship Curves
Species with Type III or early loss survivorship curves show the highest mortality in early life stages, with low mortality for those few individuals reaching a certain age and size.
Early loss curves are typical of species that produce large number of offspring and lack parental care.
Such species are r- selected species (opportunists), and include most annual plants, most bony fish (although not mouth brooders), and most marine invertebrates.
Population losses are high in early life stages
Mortality is low for the few individuals surviving to old age

34. Population numbers (N)
‘r’ and ‘K’ Selection
Two parameters govern the logistic growth of populations.
The intrinsic rate of natural increase or biotic potential. This is the maximum reproductive potential of an organism, symbolized by the letter r.
The saturation density or carrying capacity of the environment, represented by the letter, K.
We can characterize species by the relative importance of r and K in their life cycles.
K-selected species
These species exist near asymptotic density (K) for most of the time. Competition and effective use of resources are important.
Population numbers (N)
r-selected species
These species rarely reach carrying capacity (K). Their populations are in nearly exponential growth phases for much of the year. Early growth, rapid development, and fast population growth are important.
Time

35. K-Selected Species
Correlates of K-selected species
Species that are K-selected exist under strong competition and are pushed to use available resources more efficiently.
These species have fewer offspring and longer lives. They put their energy into nurturing their young to reproductive age.
K-selected species include most large mammals, birds of prey, and large, long-lived plants.
Climate
Fairly constant and/or predictable
Mortality
Density-dependent
Survivorship
Usually types I and II
(late or constant loss)
Population size
Fairly constant in time. Near equilibrium with the environment.
Competition
Usually keen. Specialist niche.
Selection favors
Slower development, larger body size, greater competitive ability, delayed reproduction, repeated reproductions
Length of life
Longer (> one year)
Leads to:
Efficiency

36. r-Selected Species
Correlates of r-selected species
Species with a high intrinsic capacity for population increase are called r-selected or opportunistic species.
These species show certain life history features and, to survive, must continually invade new areas to compensate for being displaced by more competitive species.
Opportunists include algae, bacteria, rodents, many insects, and most annual plants.
Climate
Variable and/or unpredictable
Mortality
Density-independent
Survivorship
Often type III
(early loss)
Population
size
Fluctuates wildly. Often below K.
Competition
Variable, often lax. Generalist niche.
Selection
favors
Rapid development, high rm, early reproduction, small body size, single reproduction (annual)
Length of life
Short, usually less than one year
Leads to:
Productivity

37. Population numbers (N)
Population Dynamics
Warm Up: Identify and describe three key features of the logistic growth model.
Population numbers (N)
Time

38. Demography
Demography is the study of human populations, their characteristics and changes. Demographics will measure:
Statistics about people, such as births, deaths, and where they live as well as total population size.
GO TO census.gov and obtain the current world population and the current US population.

39. Human Population Growth
The world population, now over 7 billion, is growing at the rate of about 80 million per year.
Projections put the world population at between 8 and 12 billion in 2050, with nearly all of this growth expected in the developing world.
Developing countries include: Africa, Asia, Latin America, the Caribbean, and regions of Melanesia, Micronesia, and Polynesia.
The human population has grown rapidly because of the expansion of agriculture and industrial production and lower death rates from improvements in hygiene and medicine.
The debate over interactions among population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science.
Developed countries grew at 0.1%
Developing countries grew at 1.5% (15 times faster)

40. Growth Rate & Doubling Time
Growth rate includes the birth rate, death rate, immigration and emigration. Usually calculated in percent growth using the formula of births minus deaths, plus immigration minus emigration.
If a population of 10,000 experiences 100 births, 40 deaths, 10 immigrants and 30 emigrants in a year, what is the annual percentage growth rate?
Doubling time is the time (in years) it takes for the population to double the number of people in the current population. Calculated as 70 / % growth rate
If a population of a country grows at a rate of 5% per year, the number of years required for the population to double is what?
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?
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?

41. Global Population Growth
Estimates of likely future growth of the world human population are highly uncertain and projections for 2050 range from a low of 7.7 billion to a high of 11.2 billion.
Global Human Population Growth
High fertility rate: 11.2 billion
Medium fertility rate: 9.4 billion
Low fertility rate: 7.7 billion
North America
Latin America & Caribbean
Europe
Asia & Oceania
Africa
Note: The latest ‘medium variant’ U.N. projection of 9.37 billion is nearly 500 million (4.7%) lower than the 9.83 billion projected in 1994.

42. Demographic Transitions
Demographic Transition describes the process where countries become economically developed then their birth and death rates begin to decline. In the past this was referred to as “first” and “third” world countries or “developed” and “developing”.
Currently this process is described by the different stages according to population growth:
Preindustrial stage shows little population growth due to high birth rate with high death rate.
Transitional stage is where industrialization begins, death rates drops and birth rates remain high. Rapid population growth occurs.
Industrial stage is birth rate dropping and approaching death rate. Population growth slowly declines.
Postindustrial stage are birth rate and death rate become similar and population growth slows or declines.
Post-industrial: 37 countries have reached this stage. (mainly in W. Europe) To most population experts, the challenge is to help the remaining 88% of the world to get to this stage.

43. Demographic Transition
97% of growth in developing countries living in acute poverty usually occurs during the transitional stage.
What is the optimum sustainable population of the earth based on the cultural carrying capacity?
Generalized model of demographic transition shows that the total fertility of a society decreases as the society progresses through the demographic transition.
Some developing countries may have difficulty making the demographic transition.

44. Demographic Transition
Post-industrial: 37 countries have reached this stage. (mainly in W. Europe) The challenge is to help the remaining 88% of the world to get to this stage.
initially birth rate and death rate are both high, birth rate remains high, death rate declines (because of better health care, etc.), birth rate declines and approaches death rate (mention of postindustrial phase with explanation is acceptable).

45. Size/age classes in fish
Age Structure
Age structure refers to the number of organisms of different ages.
Populations can be broadly grouped into those individuals of:
pre-reproductive age
reproductive age
post reproductive age
Analysis of the age structure of populations can assist in their management because it can indicate where most population mortality occurs and whether or not reproductive individuals are being replaced.
Size/age classes in fish

46. Human Age Structure
Age Structure in Human Populations
Human age structure varies from country to country.
In developing countries age structure tends to be in favor of younger individuals with a large proportion being under 15 years.
In developed nations, age structure is relatively even throughout the age groups.

47. Determining Population Growth
The rate at which a population grows or declines depends on its age structure. Age structure diagrams are a graphical illustration that shows the distribution of different age groups. These groups are further broken into cohorts:
Prereproductive age are persons who are not mature enough to reproduce
Reproductive age are those persons that are capable of reproduction.
Postreproductive age are those persons too old to reproduce.

48. Age Structure Diagrams
Populations with a large proportion of its people in the preproductive ages 1-14 have a large potential for rapid population growth. Those with a large proportion of people in reproductive age are experiencing rapid population growth.

49. Age Structure
Since age structure diagrams are broken down by age, demographers can obtain:
Birth rate
Maturity rate
Death rate of an entire population.
These diagrams are usually broken down by country and divided into genders.
32% of the people in developing countries were under 15 years old in 2006 versus only 17% in developed countries.
Changes in the distribution of a country’s age groups have long-lasting economic and social impacts.

50. Age Structure: United States
Today, baby boomers make up nearly half of all adult Americans and dominate the populations demand for goods and services.
Monitoring the baby boom generation in yellow.

51. Rapid Growth Diagram
A relatively large segment of the population of the country is currently in the prereproductive/reproductive years and will soon begin having children (giving the population momentum).
Pyramid shaped histograms have a birth rate that exceeds the death rate. Lower cohorts have more males and females.
Population growth is rapid in countries that have a pyramid shape.
Current modern examples include Africa, Asia, and Latin America

52. Slow/Stable Growth Diagrams
Birth rate exceeds the death rate. Population is getting larger. Pyramid shaped histogram.
In contrast, the prereproductive cohorts in county Y are about equal in size to the reproductive and postreproductive cohorts.
When the histogram shape is “box”-like, then stable or slow growth is represented.
Birth rate is almost equal to death rate.
Current examples of slow growth: USA, Australia, & Canada
Current examples of stable growth: Denmark, Austria, & Italy

53. Negative Growth Diagrams
Birth rate exceeds the death rate. Population is getting larger. Pyramid shaped histogram.
If there is declining or negative growth, then the birth rate with be less than the death rate.
Pyramids with declining populations tend to show larger numbers of older persons in their population.
Current examples: Germany & Japan

54. Developing vs. Developed
Developing (Transitional, Third World):
Higher infant mortality rate because of a shortage in prenatal and pediatric care. Thus, they have more children to ensure some survive.
Agricultural societies need children to help in the labor force.
Lower per capita income or poorer countries need children to provide an income and sometimes contraceptives are not affordable.
Women lack education and job opportunities.
Developed (Industrial, First World):
Educated and working women tend to delay childbearing.
Pension systems support people as they age.
Family planning and the ability to control fertility.
Higher cost of raising children causes people to have smaller families.
Abortion is legal.
Infant mortality higher in a country due to, for example, - contaminated drinking water - poor nutrition - poor health care- few or no educational opportunities for women.

55. Population Dynamics
Warm Up: Identify and describe three historical factors that have lead to declining death rates.
Homework: “Age Structure Diagrams”
Homework: “Population Calculations”
2000 #4 - Analyzing data (easy)
2003 #2 - Population growth and graph (hard)
2005 #2 - Demand for meat, calculations (medium)
2007 #4 – Urban vs Rural, Pollution (easy)

56. Las Vegas: 1973 (above) and 2006 (below)
Urbanization
Urbanization is the physical growth of urban areas as a result of global change. As agriculture and small-scale industry give way to modern industry, resources are drawn upon in an ever-widening area.
As urbanization increases and natural surfaces are covered or removed decreasing transpiration, increasing runoff and the groundwater supply is reduced due to loss of recharge area.
Large amounts of energy are used and waste is produced that need to be treated, both municipal and sewage.
Concentration of people can cause pollution and health problems.
Excessive noise pollution that can lead to hearing loss and excessive light pollution can cause plant and animal ecological disruption.
Las Vegas: 1973 (above) and 2006 (below)

57. Central Park, New York City, NY
Urbanization
Urban sprawl removes trees and vegetation which creates a heat-island effect which explains that urban areas trap more heat than rural areas because of the heat generated by cars, factories, furnaces, lights, air conditioners, heat-absorbing dark roofs, tall buildings and asphalt streets in cities.
Increased combustion from automobiles, airplanes and factories has made for higher particulates, NOx, SOx, lead, CO and smog. With less vegetation there is also less filtering.
Industrial processes release hydrocarbons & volatile fumes.
Most large cities have gone through city planning to develop mass transit systems and parks to help reduce some of the pollution problems.
Central Park, New York City, NY

58. Urbanization
Urbanization is the movement of people from rural areas into cities (Push / Pull)
Urban areas must import most of its food, water, energy, minerals, & other resources because of large populations
Large populations produce and consume enormous quantities of resources that can pollute the air, water & land.
Disease can easily spread in urban areas because of the high density population.
50% of the world’s people live in urban areas that occupy only 5% of the world’s land & they consume 75% of the world’s resources.

59. Immigration Push Factors Immigration Pull Factors
Urbanization
Immigration Push Factors
Rural overpopulation
Lack of food or work
Changing agricultural practices
Desire for a better education
Racial or religious conflict
Political instability
Immigration Pull Factors
Opportunity for better jobs
Chance for better housing
More reliable food supply
Opportunity for greater wealth
Freedom from village traditions
Government policy
Thomas Malthus - “diminishing returns” He argues that rising wages and improved well-being would lead to excess reproduction among the working class. A labor surplus would then cause wages to fall below subsistence levels, resulting in starvation, disease and crime. In his view, land for food production was the limiting factor in both population growth and economic development.

60. Mortality and Fertility
Infant mortality rate: The number of child and/or infant deaths.
If a mother lives in an area with a high infant mortality rate she will tend to have a lot of children to ensure some will make it to adulthood. This ensures care for aging parents and a labor force.
Infant mortality rate is higher in developing countries than in developed countries.
Along with life expectancy, the infant mortality rate is a good indicator of the quality of life of a country
Replacement-level fertility: the number of children a couple must bear to replace themselves.
Slightly higher than two children per couple. (2.2 in developed countries and 2.5 in some developing countries.)
Infant mortality higher in a country due to, for example, - contaminated drinking water - poor nutrition - poor health care- few or no educational opportunities for women.

61. Total Fertility Rates
Total fertility rate (TFR): the average number of children a woman has during reproductive years.
In 2006, the average global Total Fertility Rate was 2.7 children per woman.
1.6 in developed countries (down from 2.5 in 1950.)
3.0 in developing countries (down from 6.5 in 1950).
If fertility rate drops to replacement level fertility but the population continues to grow, this is called population momentum and can be seen in pyramid shaped age structure diagrams.
Birth rates and fertility rates have been slowed or decreased because:
Cultural/religious practices prohibited birth control.
Cultural/religious practices favored large families.
Education/Employment/Status of women is low
Reasons for decline from 1950 to present: increased/improved family planning shows fewer pregnancies, control of fertility, and choice in # of children.
Increased education of women/social status shows a delay in having children. Women enter the workforce and delay having children. Reduced need for children in the workforce because of industrialization and urbanization. Improved health care allows for more children to survive.

62. Fertility Rates
Based on current trends, it is assumed that human fertility rates will continue to decline and life expectancy will continue to increase. Developing countries are expected to broadly follow these demographic trends.
Trends in Fertility Rates
South & Central America
Africa
Asia
Developing
Developed

63. Historical Factors
Death rates have declined and births have increased because:
The Green Revolution increased food and water supplies and productivity offering better nutrition opportunities.
The Industrial Revolution improved sanitation and allowed improved personal hygiene through safer water supplies.
Advances in medicine reduced mortality rate. The improvement in prenatal or neonatal care greatly aided the decline in death rate.
Fertilizers and pesticides increased crop yields
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.
More children live past childbirth

64. Population Stabilization
Human population growth is slower than predicted but because of the large and increasing population size the world population is still expected to increase substantially before stabilizing.
Progress Towards Population Stabilization
South & Central America
Africa
Asia
Developing
Developed

65. Demographics in the USA
The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion.
In 2006, the total fertility rate in the United States was slightly > 2.0

66. Demographics in the USA
Nearly 2.9 million people were added to the U.S. in 2006:
59% occurred because of births outnumbering deaths
41% came from illegal and legal immigration. Population increase in recent years has been because of immigration
Current US
Population:
309,786,186

67. Hourly manufacturing job wage (adjusted for inflation) $3 2000 $15
47 years
Life expectancy
77 years 8%
Married women working
outside the home
81%
15%
High school
graduates
83%
10%
Homes with
flush toilets
98%
Homes with
electricity 2%
99%
Figure 9.7
Some major changes that took place in the United States between 1900 and QUESTION: Which two of these changes do you think were the most important? (Data from U.S. Census Bureau and Department of Commerce)
Living in
suburbs
10%
52%
1900
Hourly manufacturing job wage (adjusted for inflation) $3
2000
$15
Homicides per
100,000 people
1.2
5.8

68. Developed Countries
High rates of resource use because of the availability of resources, production, and waste.
Result in high levels of pollution and environmental degradation per person because of control methods, clean up, and education.
The measure of a country’s economic growth is the Gross National Product (GNP) or the Gross Domestic Product (GDP).
The Human Development Index is also commonly used to determine development.
It is estimated that a US citizen consumes 35 X’s as much as the average citizen of India and 100 X’s as much as the average person in the world’s poorest countries. (What if everyone in the world lived like we do?) Then, poor parents in a developing country would need kids to have the same lifetime environmental impact as 2 US children.
Most developed countries have a GDP that is high and a population growth rate that is low.

69. Developing Countries
China, the largest, has taken drastic population control methods.
By 2050, India is predicted to pass China. Pakistan is projected to become 3rd (the US is 3rd now.)
Russia is losing 600,000 people a year, after being the 4th largest country in 1950.
Environmentalists are concerned about resource use because developing countries are increasing their standard of living.
Russia’s declining population is because of environmental pollution, hyperinflation, crime, corruption, disease and despair.

70. India’s Population Control
India has tried population control methods with modest success. Poor planning, bureaucratic inefficiency, low status of women and lack of support have led to low success. The family planning method calls for:
Education of women including basic literacy.
Encouraged education of contraception use among women & birth spacing.
Possible problems include:
Cultural/Social issues.
Cost of programs.

71. China’s Population Control
China has used a government-enforced program, “One-Child Policy”, to reduce the fertility rate. The One-Child Policy includes:
Paid leave to women for fertility operations.
Monthly Subsidy to one-child families.
Job priorities for only children.
Housing preferences.
Additional food rations.
Monetary compensation.
Problems include:
Preference toward gender
Increase in orphans
Consequences or punishment for multiple births
Since 1970, China has used a government-enforced program to cut its birth rate in half and sharply reduce its fertility rate.
- paid leave to women for fertility operations - monthly subsidy to single-child families - job priorities for only children - housing preferences for single-child families - additional food rations for one-child families - monetary compensation for single-child families

72. Illiteracy (% of adults) 47% 17% 36% Population under age 15 (%) 20%
Percentage of world
population
17%
India
20%
China
1.1 billion
Population
1.3 billion
Population (2050)
(estimated)
1.4 billion
1.6 billion
Illiteracy (% of adults)
47%
17%
36%
Population under age 15 (%)
20%
1.6%
Population growth rate (%)
0.6%
2.9 children per women (down from 5.3 in 1970)
Total fertility rate
1.6 children per women (down from 5.7 in 1972) 58
Infant mortality rate 27
Figure 9.15
Global connection: basic demographic data for India and China in (Data from United Nations and Population Reference Bureau)
62 years
Life expectancy
70 years
Percentage living
below $2 per day 80 47
$3,120
GDP PPP per capita
$5,890

73. 1994 Global (Cairo) Conference: Population & Development
The summit at Cairo, Egypt, encouraged action to stabilized the world’s population at 7.8 billion by 2050, instead of the projected billion.
Provide universal access to family-planning services
Improve the health care of infants, children & pregnant women and improve the status of women by expanding education & job opportunities
Encourage development of national population policies
Increase men’s involvement in child-rearing responsibility & family planning and increase access to education for girls
Take steps to eradicate poverty
STOP
Describe one incentive that the government of a country could offer its citizens that would favor a reduction in the growth rate of its population. Explain how this incentive would work, and describe one possible drawback.

74. Environmental Impact
Deforestation destroys habitats and reduces biodiversity:
Farming and the creation of monocultures, housing or development projects that cause urbanization, fuel from wood, and fossil fuel recovery from mining.
Fossil fuel burning releases CO2:
Results in climate change, change in temperature and precipitation patterns changing habitats.
Intensive fishing and fish farming:
Spreads disease to native fish and causes unsustainable fish populations.
Diversion and damming of water:
For agricultural, municipal, and industrial use reduces water supplies.
Building landfills:
To accommodate increased amounts of trash.