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Populations 10-15% of your APES Exam Populations • Most species live in groups. This has several advantages – Increased protection from predators – Increased chances of mating – Division of labor Factors that affect Population Viability Increase Viability Decrease Viability Favorable environment Unfavorable environmental conditions High natality (births per 1000) Low natality Generalized Niche Specialized niche Satisfactory Habitat Habitats not satisfactory or has been seriously impacted Few Competitors Too many competitors Suitable predatory defense mechanism Unsuitable predatory defense mechanisms Adequate resistance to diseases and parasites Little or no suitable defense mechanisms against diseases or parasites Able to migrate Unable to migrate Flexible- able to adapt Inflexible- unable to adapt Sufficient food supply Deficient food supply Carrying Capacity (K) • The number of organisms that can be supported in a given area sustainable • Varies from species to species and subject to change over time Regulating Factors • Density independent factors: drought, flood, natural disasters • Density dependant factors: number of resources, competition, disease Biotic Potential • The maximum rate at which a population can grow. • Its biotic potential, given optimal conditions, occurs when resources are unlimited. • Factors that influence biotic potential include – – – – – Age at reproduction Reproductive life span Average death rate under ideal conditions Frequency of reproduction Number of offspring Populations • If a population is left unchecked, population growth rate can increase exponentially and take on the look of a j-curve. Predator Prey Populations • Predation only removes the very old, very young and weak of a prey population • If the predators do not keep the prey population in balance, the carrying capacity is exceeded and the prey may starve. • Predator and prey populations are closely interdependent S-shaped curves • The s-shaped curve is uses to describe the pattern of growth over extended periods of time when organisms move into an empty niche. • Growth rates are density-dependent • Eventually the population will stabilize around the carrying capacity. Thomas Malthus • Political economist in the 19th century who saw the decline on living conditions and blamed it on the following – Overproduction of the young – Inability of resources to keep up with increased human population – Irresponsibility of the lower classes. Thomas Malthus • He suggested the following to combat the problem of overpopulation. – Lower class families should be regulated so poor families do not produce more children than they can support • There should be “positive checks” such as starvation and disease that occur naturally • “preventative checks”- postponement of marriage to keep the birth rate down Reproductive Strategies R- strategists K-strategists Mature rapidly Mature slowly Short lived Long lived Tend to be prey Tend to be both predator and prey Have many offspring and overproduce Have few offspring Low parental care High parental care Generally not endangered Most endangered species are K-strategists Wide fluctuation in population density (booms and busts) Population stabilizes near carrying capacity Population size limited by density-independent Density-dependent limiting factors to factors (climate, weather, natural disasters, population growth stem from intraspecific requirements for growth) competition and include predation, parasitism, and migration Tend to be small Then to be larger Type III survivorship curve Type I or II survivorship curve Examples: most insects, annual plants, bacteria, rodents Examples: humans, elephants, cacti and sharks Survivorship Curves • Show age distribution characteristics of species, reproductive strategies and life history. • Reproductive success means how many organisms make it to maturity and reproduce Survivorship Curves Type Descriptions I Late Loss Reproduction occurs fairly early in life. Most deaths occur at the limit of biological life span. Low mortality art birth. High probability of surviving to advanced age. Advances in prenatal care, nutrition, disease prevention and cures mean longer life spans for humans. Examples: humans, annual plants, sheep and elephants. II Constant Loss Individuals in all age categories have fairly uniform death rates. Predations affecting all age categories is primary means of death. Typical of organisms that reach adult stages quickly. Examples: rodents, perennial plants and songbirds. III Early Loss Typical of species that have great numbers of offspring and reproduce for most of their lifetime. Death is prevalent for younger members of the species (environmental loss and predation) and declines with age. Examples: sea turtles, trees, internal parasites, fish and oysters. Human Population • Rapid growth of the worlds human population over the past 100 years as primarily been due to a decrease in death rates • These factors have reduced death rates: – Increased food and more efficient distribution that result in better nutrition – Improvements in medical and public health technology – Improvements in sanitation and personal hygiene – Safer water supply Human Population • Human population has had 3 surges – The use of tools and fire – The agricultural revolution when humans stopped being hunter-gathers and began to raise crops – The industrial and medical revolutions within the last 200 years. Population Change • CRUDE: per 1,000 • Crude birth rate: births per 1,000 people • Crude death rate: deaths per 1,000 people Population change= (crude birth rate + Immigration) – (crude death rate + emigration) Practice Problem- Population Change • In 1950, the population of Devinville was 20,000. The birth rate was measured at 25 per 1,000 population per year. Immigration was measured at 600 per year. Death rate was measured at 7 per 1,000 per year. While emigration was measured at 200 per year. By how much did the population increase or decrease in that year. Practice Problem- Population Change ANSWER Population change= (crude birth rate + Immigration) – (crude death rate + emigration) = (25(20) + 600) (7(20) + 200) = + 760 The population grew from 20,000 to 20,760 Why multiply by 20?? Remember that CRUDE means per 1,000… in this problem we started with 20,000 people… Human Population- Actual Population rate • The actual population rate is calculated by the following formula Actual Growth rate (%)= birth rate- death rate 10 Practice Problem- Actual Growth Rate • The United states had a birth rate of 14.6 live births per 1,000 population in one year, compared to India’s birth rate of 22.2 in that same year. The death rate in that year for the United States was 8.3 deaths per 1,000 population compared to India’s rate of 6.4 – Calculate the population growth rates (%) for both the United States and India for that year. Practice Problem- Actual Growth Rate ANSWER Actual Growth rate (%)= birth rate- death rate 10 United States: 14.6-8.3 = 0.6% 10 India: 22.2- 6.4 = 1.6% 10 Human Population • The current growth rate of the world is 1.4%, this would add 80 million people to the 7.3 billion people on planet every year Human Population Distribution • Between 2000 and 2030 most growth will occur in less developed countries in Africa, Asia and Latin America. • More developed countries in Europe and North America will have growth rates less than 1%. • Some countries such as Russia, Germany, Italy and Japan will experience negative growth Fertility Rates • Replacement Level Fertility: a couple only has enough kids to replace themselves = 2.1 • RLF rates are lover in moderately developed countries and higher in less developed countries • Total Fertility Rate: the number of children a woman will have in her lifetime. • The country of Niger in Africa leads the world’s TFR at 7.46 Fertility Rates • Despite half of the worlds population being below RLF the population will still grow quickly. This is because of nations with above RLF levels and the large numbers of younger females who have not yet had children. • Declines in fertility rates can be attributed to the following: – Urbanization- reduces the need for child workers, higher cost of living – Personal and government acceptance of family planning – Increased numbers of females in the workplace or getting an education (female empowerment) – Postponing marriage and having careers. Fertility Rates • Effects of RLF (without looking at immigration): population decline and population aging. • The greatest TFR in the United States happened after WWII (baby boomers) • New immigrants and their descendants are projected to contribute to 66% of the expected growth by 2050. Fertility Rates Rule of 70- Doubling Time • If you are given a percent of population increase and asked to find how many years it will take that population to double. Take off the percentage and put it under 70. • Example: Growth rate of 2% 70 = 35 years 2 Demographic Transition Age Structure Diagrams • Determined by birth rate, generation time, death rate and sex ratios. Age Structure Diagrams Strategies for Sustainability • Provide economic incentives for having fewer children • Empower women- Low status of women is the number one problem • Education usually leads to higher incomes. Higher incomes decrease the need for extra children to take care of older parents. • More education leads to having children later in life • Provide government family planning. • Improve prenatal and infant health care. Women would not need to have more children if their children survive • Increase economic development in less developed counties through free trade and private investment with tax incentives Case Study and National Policy- China • Between 1972 and 2000 China cut it’s crude birth rate in half (TFR dropped from 5.7 to 1.8) • Most effective and strictest programs in the world • Incentives such as extra food, larger pensions, better housing, free medical care, free tuition, and salary bonuses for parents who limit their number of children • Couples are encouraged to postpone marriage and only to have 1 child • If the first is a female they are able to have one more child and keep their incentives • Physicians receive a bonus for sterilization procedures • Couples pushed to terminate unplanned pregnancy • Penalties include fines, loss of land , less food, decrease in farm supplies, loss of government benefits, discharge from Communist Party. Case Study and National Policy- India • In 1952 India began its first involving vasectomies. family planning program • Reasons for India’s failures (population of 400 million) – Poor planning • In 2000, India’s population – Low status of women was 1 billion or 16% of the – Favoring male children worlds population. – Insensitivity to cultures • 1/3 of the population earns • Tubal Ligation is preferred less than 0.40 a day. today • Cropland has decreased by • Condoms are free although used by less than 10% 50% per capita since 1960 • Other birth control methods • In the 1970’s India only used by upper class implemented a mandatory sterilization program Impacts of Human Population Growth • A large portion of the world is malnourished (25%) • Areas with the greatest malnutrition are; Africa, Asia and parts of Latin America (also areas with highest TFR) • Factors contributing to malnutrition: – Poverty – Droughts, which will only increase as the impact of global warming becomes more severe – Populations that have surpassed their carrying capacity – Political instability and wars that will cause mass migrations – Pestilence (fatal epidemic diseases) – Foreign investors who own large landholdings and whose sole motivation is money (selling food to highest bidder; exploiting it) Impacts of Human Population GrowthAIDS- United States • In the United States, more than half a million people have died of AIDS or complications of it since 1981. • 15,000 US citizens die annually • 1 million people live with the virus • 40,000 become infected each year • African Americans (13% of US population) account for ½ of new infections and 1/3 of all AIDS-related deaths • African American males are 7X more likely to get the HIV infection than Caucasian males • African American females are 20X more likely to get the HIV infection than Caucasian females • The fastest growing population of new infections are 15-24 year olds. Impacts of Human Population GrowthAIDS- Worldwide • 25 million people have died from AIDS and 2.8 million died in 2006 alone. • WHO says AIDS could kill 31 million people in India and 18 million people in China by 2025. • The toll from AIDS over the next 25 years will go far beyond the 34 million people thought to have died from the Black Plague or the 20-40 million people who died of the Spanish Flu • AIDS is the leading cause of death in Africa, which has accounted for nearly half of all the global AIDS deaths. • In some countries AIDS reduces life expectancy to less than 40 years Impacts of Human Population GrowthSmoking • WHO estimates by 2020, tobacco-related illnesses will be the worlds leading killer. And will be responsible for more deaths than AIDS, TB, road accidents, murder and suicide combined. Impacts of Human Population GrowthOther Health Effects • Tuberculosis is the leading cause of death in many poorer countries and its economic impact on global economies is estimated at 12 billion dollars. • Each year 500 million people are infected with Malaria- leading to 1 million deaths. 75% of the infected are children in Africa. Developments of new strains of Malaria are more common and they are less reactive to drug therapy Impacts of Human Population GrowthPandemics • Spanish Flu of 1918-1919 killed between 2040 million. 28% of Americans were infected. Most devastating pandemic in the recorded in world history. • Bird Flu (H1N1) could kill as many as 7 million people and infect 1/3 of the population if it is passed person to person Net Primary Productivity • NPP: the total amount of solar energy converted into biochemical energy through photosynthesis minus the energy needed by those plants for their functions. • It is a quantifiable measure f resources available on earth • Estimated that there is 150 billion tons of organic matter per year (without human activity) • Humans have cause a 12% decline in NPP through deforestation alone • Humans use about 27% of the NPP for their own purposes. • In theory, using 100% NPP would support about 15 billion people. Factors that Affect Resource Utilization Factor Description Energy Resources One average American consumes as much energy as 500 Ethiopians or 35 people from India Environmental Degradation Increased population size = increased erosion, desertification, pollution, impact on ozone layer, gases that contribute to global warming Exploitation of natural resources as a function of GDP The richest 20% of the world’s population contribute to resource depletion of energy and raw materials. This leads to Pollution. The poorest 20% are being forced to cut down trees and land for their own personal use Factors that Affect Resource Utilization Factor Description Extinction of animal and plant species. Close to 50% of all species on earth could be on the path to extinction within the next 100 years. Political unrest Affects employment, food distribution and standard of living- thus affecting utilization of resources Population Density Density, more than population size, has a greater effect on pollution and use of energy. Population size Large numbers of people lead to large numbers of habitat destruction Poverty 20% of the worlds richest countries control 80% of the worlds wealth. The poorest 20% only control 1.8% of the wealth.