Chapter 5 Populations Chapter 6 Humans In the Biosphere A. Geographic distribution - (range) area inhabited by a population B. Population density-number of individuals per unit area ex: 200 people/ km 2 C. Growth rate- increase or decrease of number of individuals in a population over time. I. Characteristics of Populations II. 3 Factors that Affect Population Size A. number of births B. number of deaths C. number of individuals entering (into- immigration) or leaving (exiting- emigration) a population D. Population grows when birthrate is greater than deathrate. III. Exponential growth - when the individuals in a population reproduce at a constant rate. A.Population becomes larger and larger until it approaches an infinitely large size. B. Under ideal conditions with unlimited resources, a population would grow exponentially (J-shaped curve) IV. Logistic Growth - when growth slows or stops following a period of exponential growth (S-shaped curve) A. carrying capacity (K)- B. Growth levels off, so the average growth rate is zero. largest # of individuals of a population that an environment can support V. Limiting factor -factor that causes population growth to decrease A. Density-dependent limiting factor - limiting factor that depends on pop. size 1. Ex: competition, predation, parasitism, disease, crowding 2. Has greatest influence when pop. is large & dense; does not affect small, scattered pop. as greatly 3. Competition- when pops. become crowded, they compete for food, water, space, sunlight, other resources 4. Predation- regulation of a pop. by predation is a predator-prey relationship Wolf and Moose Populations on Isle Royale B. Density-independent limiting factors -affect all pops in similar ways, regardless of the pop. size. 1. Ex. weather, drought/floods, fire, human activity (clear-cutting, damming rivers, development) A.Began growing more rapidly due to advances in agriculture and industry. B. Death rates- reduced due to improved sanitation, medicine, healthcare, while birthrates remained high. 5-3 VI. Human Populations Human Population Growth C. Demography-study of human population growth 1. past century- pop. growth in US, Japan, Europe has slowed 2. Demographic Transition, a huge change in birth and death rates. 5-3 D. 3 stages of Dem. Trans: 1. Stage 1- high birthrate; high death rate 2. Stage 2- birthrate high; death rate drops 3. Stage 3-birthrate drops; pop growth slows 5-3 E. Age-structure diagram shows the pop. of a country broken down by gender and age group; can predict future growth of pop. U.S. Population 1. US- nearly equal no. of people in each age group 2. predicts a slow but steady growth rate for the near future Percentage of Population 5-3 Rwandan Population Percentage of Population 3. Rwanda- many more children/ teenagers, than adults. 4. diagram predicts pop. will double in about 30 years 5-3 F. To predict human pop. growth, demographers must consider age structure and disease. 1. If growth does not slow damage to the environment and global economy. 2. Science, technology, & changes in society may limit the negative impact of population growth. 5-3 6-1 I. Human activities affect the biosphere. A. Hunting-gathering- isolated parts of the world B. Agriculture -Irrigation, fertilizers, pesticides C. Industrial Revolution to Present 1. Increased pollution of air, water, soil by fossil fuels 2. Increased human waste and increased development places stress on native plants/ animals; consumes farmland D. Pollution contamination of soil, water, or air 1. has increased as countries become industrialized 2. Pollutant - harmful material that can enter the biosphere through the land, air, or water 3. Air Pollution caused by burning of fossil fuels that release pollutants that cause smog a. example: driving cars, flying planes, heating homes, factories b. example of air pollutants dust, smoke, ash, CO, sulfur oxides -Strict emissions and clean-air regulations have improved air quality c. Causes Acid rain- sulfuric acid/nitric acid from the burning of fossil fuels mix with water vapor forming low pH rain (car exhaust = nitric acid; coal-burning factories = sulfuric acid) Emissions to Atmosphere Nitrogen oxides Sulfur dioxide Chemical Transformation Nitric acid Sulfuric acid Condensation Precipitation Acid rain, fog, snow, and mist Dry Fallout Particulates Gases Power generation Ore smelting TransportationIndustry *Acid rain damages plants, kills aquatic organisms, erodes buildings and monuments, depletes soil of nutrients e. Global warming- cycle or human activity ?- CO 2 levels have increased over past 200 yrs-intensifies greenhouse effect d. Burning fossil fuels releases Carbon Dioxide into the atmosphere. - Excess CO 2 can contribute to the greenhouse effect thought to be the cause of global warming f. Greenhouse Effect *Atmospheric gases that trap the heat energy of sunlight and maintain Earth's temperature range include: carbon dioxide methane water vapor Atmosphere Earths Surface Greenhouse gases trap some heat Some heat escapes into space Page 87 g. Monitor ozone layer and global climate system 1. Ozone layer- O 3 -protects Earth from UV radiation can cause cancer, eye disease, tissue damage in plants 2. CFCs (Chlorofluorocarbons) destroys ozone layer *found in aerosols and coolants * have been reduced 4. Water Pollution caused by contaminants from sewers, industries, farms, and homes that enter lakes, rivers, groundwater and oceans *Sewage, chemical waste, fertilizer, and dirty wash water enter the water systems Contour Plowing Terracing II. Renewable and nonrenewable resources A.Renewable resources (rnr)- can regenerate (if living) or be recycled (if part of biogeochemical cycles) Ex: trees, water B. Nonrenewable resources- cannot be replenished by natural processes, are in limited amounts, once they are gone they are gone!! Ex. Fossil fuels such as coal and oil, gold, silver, copper C. Renewable or nonrenewable? 1.Depends on if the loss is large enough to change an ecosystem forever ex: coral reefs 2. ex: single tree=renewable resource, but an entire pop. of trees may change the entire ecosystem III. Biodiversity-sum total of the genetically based variety of all organisms in the biosphere A. Ecosystem diversity-variety of habitats, communities, and ecological processes in the living world. B. Species diversity is the # of different species in biosphere; increases moving towards equator. C. Genetic diversity is the sum total of all the different forms of genetic information carried by all organisms living on Earth today. Three types of diversity in ecosystems: IV. Importance of Biodiversity A. Plants and some animals produce compounds that are beneficial B. food, industry, medical- painkillers, antibiotics, antidepressants ;cancer/heart drugs/ high blood pressure ex: rosy periwinkle and digitalis Rosy periwinkle digitalis Foxglove V. Threats to Biodiversity 1. Loss of habitat- degradation (damage by pollution); fragmentation (split into pieces) 2. Hunting- food, fur,pets (birds), poaching 3. Introduced species- may become invasive species (lack predators from homeland); wipe-out native pops. Ex: zebra mussels,leafy spurge, goats Leafy spurge Zebra mussel Zebra mussels can attach to native mussels, killing them. Zebra mussels filter plankton from the surrounding water. This filtering can increase water clarity, which might cause more aquatic vegetation to grow at deeper depths and more dense stands. If a lake has high numbers of mussels over large areas, this filter feeding could impact the food chain, reducing food for larval fish. This plant is an invasive, deep-rooted perennial herb that is native to Eurasia; plant spreads through explosive seed release and vigorous lateral root growth, forming large, patches that can dominate rangeland, pastures, prairies and other areas in the Great Plains region of North America, killing native plant species. 4. Pollution DDT-softened shells of birds eggs - osprey, brown pelican, eagle population threatened b. Biological magnification concentration of harmful substances increase at higher trophic levels; DDT banned US- 1970s a. Rachel Carson Silent Spring- book about dangers of biological magnification VI. Conservation- management of resources, habitats, and wildlife 1. US Endangered Species Act-1973-illegal to harm endangered or threatened species 2. Expand National Parks or green space in cities 3. Habitat corridors-strips of land that allow migration 4. Reintroduction programs- breed animals, then release back into wild 5. Identify global hot spots-(organisms are in danger of extinction due to human activity); work on protecting those habitats; often endemic species (found no where else in the world!!) Population density is the number of individuals A. that are born each year. B. per unit area. C. that immigrate. D. that emigrate. 5-1 When the birthrate of a population exceeds its death rate, the population A. decreases. B. increases. C. stays the same. D. increases then decreases. 5-1 An S-shaped curve on a graph of population growth is characteristic of A. exponential growth. B. logistic growth. C. carrying capacity. D. delayed growth. 5-1 Exponential growth in a population slows down or stops as A. resources become limited. B. rate of immigration increases. C. rate of emigration decreases. D. birth rate increases. 5-1 Exponential growth rate means that each new generation of a population A. adds the same number of new individuals as the previous generation did. B. increases at the same rate as the previous generation C. is the same size as the generation before. D. increases by a varying amount. 5-2 A limiting factor that affects all populations in similar ways regardless of their size might be A. drought. B. disease. C. predation. D. crowding. 5-2 Which of the following would be a limiting factor directly affecting the panda population of China? A. programs that educate people about endangered species B. capture of some pandas for placement in zoos C. laws protecting habitat destruction D. a disease that kills bamboo plants 5-2 Density-dependent factors operate most strongly when a population is A. large and dense. B. large but sparse. C. small and sparse. D. small, but growing. 5-2 Within a limited area, if the population of a predator increases, the population of its prey is likely to A. increase. B. decrease. C. remain about the same. D. become extinct. 5-2 Which of the following is a density-independent factor affecting populations? A. predation B. disease C. a destructive hurricane D. parasites 5-3 The size of the human population began to increase exponentially after the A. bubonic plague. B. development of plowing and irrigation. C. Industrial Revolution. D. development of the first cities. 5-3 Which of the following is NOT a potential limiting factor of human population growth? A. famine B. medicine C. war D. disease 5-3 After the demographic transition is complete, a population A. grows rapidly. B. grows slowly. C. begins a period of rapid decline. D. stays about the same size as time passes. 5-3 An age-structure diagram shows a breakdown of a population by A. location and age group. B. age group and gender. C. birthrate and death rate. D. age group and emigration rate. 5-3 Since the mid-1960s, the average annual growth rate of the human population has A. remained about the same. B. failed to show a consistent pattern. C. increased. D. decreased.