Unit 3: Populations
Population Percent Change formula
% Change+ (P present/future- P past or present) /P past or past or present * 100% Ex: In 1980, the population of a city was 250,000. In 1990, the population of the city grew to 280,000. Calculate the % change. Answer: 12%
Demographic Transition (Stage 4 Post-Industrial)
* Birth rates equal, or are less than, mortality rates. *Zero population growth is achieved. *Standard of living is high. * Examples: Japan, most western European countries, Russia.
Economic Impact of AIDS
* HIV and AIDS delay economic growth by destroying human capital. * Infections place economic burdens on all countries (but more on less-developed countries) for treatment and the future of economic stability and societal structure (orphans). * Increases mortality results in smaller skilled labor force composed of younger workers resulting in reduced productivity-lower gross domestic product. * With fewer younger people, the tax is reduced, which reduces funds for treatment and education. * With countries in economic and social disaray due to AIDS, foreign investments are reduced.
J Curves
*If a population is left unchecked the maximum population growth rate can increase exponentially and takes on a j-shaped curve. *Arithmetic ( linear) growth rate: example 1, 2, 3, 4, 5, 6... *Geometric (exponential or j-shaped) growth rate: example 1, 2, 4, 8, 16, 32, 64...
Thomas Malthus
*In 1798, an English mathematician, Thomas Malthus, publish his theories on limited versus unlimited resources availability and its effect on population growth. *Given unlimited resources a population will grow as a J curve. *War famine and disease will control the size of the human population. *Human food resources are in excess of human requirements it is a distribution and economics that cause malnutrition and starvation.
India
*In 2000, India's population reached one billion, or 16% of the world's population. *In 1952, India began its first family planning program. It was not successful due to: * Mandatory sterilization laws * Poor Administration and planning * Low status of women * Favoring male children ( having more children if females were born) * Government insensitivity to cultures * Religious objections
Factors that cause Malnutrition
*Poverty *Droughts (which will become more frequent due to global warming) * Populations that have surpassed their carrying capacity *Political instability, wars, and so on that result in migrations *Pestilence *Foreign investors who own large landholdings and whose sole motivation is profit.
Carrying Capacity (K)
*Refers to the number of individuals that can be supported in a given area sustainably. It varies from species to species and is subject to change over time. *Limiting factors- factors that keep population size and balance with the carrying capacity examples include: 1)Food availability 2)Space 3)Oxygen content in aquatic ecosystems 4)Nutrient levels in soil profile 5)Amount of sunlight *Population decreases the carrying capacity decreases. *Populations will decrease if they exceed the carrying capacity.
S-Curve
*S shaped curve are used to describe the pattern of growth over an extended period of time. *Population growth rates are density-dependent and are characterized by maximum population growth rate coupled with the carrying capacity of the environment. *Population size initially increases due to unlimited resources for a small population. * As resources become limited the population growth rate slows down stabilizes around the carrying capacity.
Biotic Potential
*The maximum rate at which a population can grow when resources are unlimited ( food, space, water, etc).
Rule of 70
*To find doubling time of population, growing at a given annual percentage rate, divide the percentage number into 70 to get the number of years required for the population to double. Ex: at a 10% annual growth rate, the doubling time is 70/10= 7 years * To get the annual growth rate, divide 70 by the doubling time and add a percent % sign. Ex: 70/7 + 10% annual growth rate.
Human Population Distribution
* In 1800, the vast majority of the world's population (65%) resided in Asia and Europe. * By 1900, 25 % of the human population lived in Europe largely due to the Industrial Revolution. *Between 2000 and 2030, most of the growth will occur in the less developed countries in Africa, Asia and Latin America, whose growth rates are much higher than those in more developed countries. *The more-developed countries in Europe and North America will have growth rates less than 1%. *Some countries such as Germany, Italy, Japan, Russia will have negative growth rates.
Demographic Transition (Stage One Pre-Industrial)
* Living conditions are severe *Medical care is poor. * Food supply is limited due to poor agricultural techniques, limited food preservation and pestilence. *Birth rates are high to replace individual lost through high mortality rates. * Due to Aids, sub-Saharan Africa has reverted back to this stage.
Demographic Transition (Stage Two Transitional)
* Occurs after the start of industrialization. * Standards of hygiene, advance medical techniques, improved sanitation, cleaner water supplies, and higher level of education drive mortality rates down.
Strategies for Population Stability
* Provide economic incentives for having fewer children * Empower and educated women *Education usually leads to higher incomes. Higher incomes decrease the need for having extra children to take care of older parents or work on a farm. * Higher education usually results in having children later in life. * Provide government family services(e.g. sex education, birth control, sterilization, abortion) * Improve prenatal and infant care. * Increase economic development in less-developed countries through free trade and private investment with tax incentives.
Historical Human Population Sizes
* The rapid growth of the world's human population over the past one hundred years has been primarily due to a decrease in the death rate. *In 1900, the overall death rate in the United States was 1.7 % in 2000 the death rate had dropped to 0.9%. *Children in 1900 were ten times more likely to die than children in 2000.
Total Fertility Rate (TFR)
* Total Fertility Rate is the average number of children that each woman will have during her lifetime. *Urbanization-results in higher costs of living and lower TFR. Urbanization does not require a lot of children to support a farm. * Education of women-results in a higher standard of living. there is a correlation between higher education level of women and fewer children. * Birth control methods are more accessible and accepted. * In more-developed countries, marriage is being delayed as individuals focus on career goals. *Vaccination and medical care. With more access to health care and preventative vaccinations, more young children are surviving-so fewer need to be produced to replace those who would have died.
Demographic Transition (Stage 3 Industrial)
* Urbanization decreases the economic incentive for large families. *Cost of supporting an urban family increases and parents are discourages from having large families. * Leisure time is available. *Retirement nets in place. * Birth rate drops, approaching death rate. *Ex: China
Impacts of Human Population Growth
* When left unchecked, population growth often results in hunger. *25 % of the world's population is malnourished. Areas most impacted are Africa, Asia, and parts of Latin America- regions with high TRFs.
Living in Groups
* most organisms live in groups ( flocks, schools, nest, packs, etc) *living in groups provides the following advantages: 1) increase protection from predators (e.g. more eyes watching) 2) increase chance for mating (large ranges makes finding mates difficult.) 3) division of labor (e.g. bees: protect the hive, build nests, lay the eggs, rear the young.) 4) Greater success in finding, killing, or defending prey items
Suvivorship Curve
*A graph showing the number of proportion of individual surviving at each age for a given species or group (e.g, females/males) 1) Type 1 survivorship curves -High survival in early and midlife followed by rapid decline of survivorship in later life. Example: Humans 2) Type 2 survivorship curves- Show a roughly constant morality rate regardless of age. Example: Birds 3) Type 3 survivorship curves- the greatest morality rate is experienced early on in life with relatively low rates of death for those surviving this bottleneck. Characteristic of species that produces a large number of offspring Example: Frogs
Factors That Affect the Biotic Potential
*Age of reproduction *Frequency of reproduction *Number of Offspring produced *Reproductive lifespan *Lifespan average *Average death rate under ideal conditions
China
*Between 1972 and 2000, China reduced its crude birth rate half (TFR dropped from 5.7 to 1.8) *Lower mortality rates with one-child policy have resulted in dramatic aging of China's population. *By 2020, they said about 25% of China's population is expected to be over 65 resulting in challenges to medical and insurance services. * Family program is mobile and reaches rural areas. * Incentives of extra food, larger pensions, better housing, free school tuition, and free medical care and salary bonuses for parents who limit family size. * After first child, the mother is required to wear and intrauterine device. * Physicians receive bonuses for sterilizations.
Factors that Affect Resource Utilization (Population-Size Dependent)
*Carrying Capacity(k) * Energy resources. *Environmental degradation. *Exploitation of natural resources as a function of gross domestic product. * Extinction of animal and plant species. * Famine. * Political unrest, *Pollution. *Poverty. * Consumption of resources.
Density Dependent Factors
*Density dependent factors intensify as the population size increases affecting each individual more strongly. *Increasing in population size reduces available resources limiting population growth. *Examples: 1) there is a reduction in the food supply that restricts reproduction results in fewer offspring. 2) The competition for space to establish territories is a behavioral mechanism that may restrict population growth. 3) Predators concentrate in areas where there is a high concentration of prey.
Factors That Affect Population Viability
*Environmental conditions ( light, temperature, nutrients etc.). *Birth rate (natality). *Presence of competitors. *Predatory defense mechanisms. *Resistance to disease and or parasites. *Ability to migrate. *Ability to adapt. *Food supply.
Density Independent Factors
*Factors that affect all individuals in the population of regardless of population size *Examples: 1) Weather 2) Climate 3) Freezes 4) Fire 5) Hurricane 6) Floods
Age Structure Diagrams (Less Developed Countries)
Age-Structure diagrams are determines by birth rates, generation time, death rate and sex ratios. In the age structure diagram for Mexico in 1975, * the base is large (large number of pre-reproductive children) *Potential for large population growth as these children enter a reproductive age and have children. (Population momentum)
Population Dispersal
1) Clumped - some areas within the habitat are dense with organisms; others contain few members 2)Linear- individuals are in straight lines 3) Random- little interaction between members of the population leading to random spacing patterns 4) Uniform- fairly uniform spacing between individuals
R-strategist characteristics
1) Growth Pattern *Small body *Boom bust population fluctuation *Population size limited by density independent limiting factors 2) Environment *Unstable or recently disrupted *Low diversity *Low resources 3) Characteristics of Offspring *Low parental care with early reproductive maturity *Large numbers *Short life span *Generally not endangered 4) Type 3 survivorship curve Examples: weeds, most insects, rodents, annual plants.
K- Strategist Characteristics
1) Growth pattern *Larger Body * Population tends to stabilize around carrying capacity * Birth rates drop as a population approaches K 2) Characteristics of Offspring *High level of parental care with delayed reproductive maturity *Smaller number of offspring produced *Longer life span Examples: elephants, humans, oak trees, cacti, sharks
Factors that have Reduced Human Death Rate
1) Increased food production 2) More efficient distribution of food resources 3) Improvements in medical and public health technology 4) Improvements in sanitation and personal hygiene 5) Safer water supplies
Malthusian Catastrophe
A return to subsistence level conditions as a result of population growth outpacing agriculture production.
Annual Percentage Growth Rate
Annual percentage growth rate is the growth rate divided by the number of years.
Density Dependent Factors Vs Density Independent Factors
Compare and Contrast
r-strategist vs K-strategist
Compare and Contrast
Human Population Growth Diagram 1750-2050
Human Population has had three surges in growth due to: *Use of tools and fire *Agricultural Revolution * Industrial Revolution and advancement in health care
Age Structure Diagram (More Developed Countries)
In an age structure diagram for a more devloped country like France, *Population structure and growth are fairly constant; population is stable. *Life expectancy is long; most death occurs in later years.
Demographic Transition
Process that has occurred during the past century, leading to a stabilization of population growth in the more highly developed countries .
Population Change Calculation (Example)
Q: On Jan 1, 1950, the population of a small suburb in Los Angeles was 20,000. Birth rate was 25 per 1,0000 population. Death rate was 7 per 1,000 population. Immigration was 600 per year. Emmigration was 200 per year. By how did the population increase or decrease by Jan. 1, 1951? (CBR+immigration)-(CDR+emmigration) Answer: The population grew from 20,000 to 20,760.
Carrying Capacity Diagram
Understanding the diagram: * Overshoot: The amount by which humanity's resource use, as measures by its ecological footprint, has surpassed Earth's long-term capacity to support us. *Die-off: a period in which a significant proportion of a population dies naturally, usually within a short time.
