Understanding Human Population Growth and its Impact on Ecosystems, Slides of Biology

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Population Ecology and Ecosystems Concepts and Applications: Chapters 40 & 43 Docsity.com Ecology • Certain ecological principles govern the growth and sustainability of all populations • Human populations are no exception Ecology: The study of how organisms interact with one another and with their environment Docsity.com Population Age Structure • Divide population into age categories • Population’s reproductive base includes members of the reproductive and pre- reproductive age categories Docsity.com Density & Distribution • Number of individuals in some specified area of habitat • Crude density information is more useful if combined with distribution data clumped nearly uniform random Fig 40.2 Docsity.com Determining Population Size • Direct counts are most accurate but seldom feasible • Can sample an area, then extrapolate • Capture-recapture method is used for mobile species Mark and Recapture # marked Captured = Number released Total Captured Total Pop Docsity.com Zero Population Growth- ZPG • Interval in which number of births is balanced by number of deaths • Assume no change as a result of migration • Population size remains stable Docsity.com Per Capita Rates • Rates per individual • Total number of events in a time interval divided by the number of individuals • Per capita birth rate per month = Number of births per month Population size Docsity.com Exponential Growth • Population size expands by ever increasing increments during successive intervals • The larger the population gets, the more individuals there are to reproduce Fig 40.4 Docsity.com Biotic Potential • Maximum rate of increase per individual under ideal conditions • Varies between species • In nature, biotic potential is rarely reached Docsity.com Limiting Factors • Any essential resource that is in short supply • All limiting factors acting on a population dictate sustainable population size Space Food Shelter Temperature Mates Pollution Disease Docsity.com Carrying Capacity (K) • Maximum number of individuals that can be sustained in a particular habitat • Logistic growth occurs when population size is limited by carrying capacity Docsity.com Overshooting Capacity • Population may temporarily increase above carrying capacity • Overshoot is usually followed by a crash; dramatic increase in deaths Fig 40.7 Docsity.com Resetting the Carrying Capacity • Major changes in environment can change the carrying capacity of a local system Fig 40.6 Docsity.com Density-Dependent Controls • Logistic growth equation deals with density-dependent controls • Limiting factors become more intense as population size increases • Disease, competition, parasites, toxic effects of waste products Docsity.com Life Table • Tracks age-specific patterns • Population is divided into age categories • Birth rates and mortality risks are calculated for each age category Docsity.com Survivorship Curves TYPE II Fig 40.8 Docsity.com Human Population Growth • Population now exceeds 6 billion • Rates of increase vary among countries • Average annual increase is 1.26 percent • Population continues to increase exponentially Docsity.com Future Growth • Exponential growth cannot continue forever • Breakthroughs in technology may further increase carrying capacity • Eventually, density-dependent factors will slow growth Population Momentum • Lowering fertility rates cannot immediately slow population growth rate. Why? • If every couple had just two children, population would still keep growing for another 60 years Docsity.com Resource Consumption • United States has 4.7 percent of the world’s population • Americans have a disproportionately large effect on the world’s resources • Per capita, Americans consume more resources and create more pollution than citizens of less developed nations Docsity.com Effects of Economic Development • Total fertility rates (TFRs) are highest in developing countries, lowest in developed countries • When individuals are economically secure, they are under less pressure to have large families Docsity.com Types of Interactions • Neutral • Commensalism • Mutualism • Competition • Predation • Parasitism Who benefits? Spp 1 Spp 2 0 0 Y 0 Y Y N N Y N Y N Community Ecology Docsity.com Competition • Competitive Exclusion – Paramecium • Resource Partitioning – Fruit eating birds, Barnacles Community Ecology Docsity.com Predator-Prey Interactions • The Classic Lynx / Hare system Community Ecology Docsity.com Food Webs can be Disrupted • Natural Disasters • External inputs – Pesticides, Pollution Ecosystems Docsity.com Ecosystems Fig. 43.14, p. 746 ATMOSPERE OCEAN LAND evaporation from ocean 425,000 precipitation into ocean 385,000 evaporation from land plants (evapotranspiration) 71,000 precipitation onto land 111,000 wind driven water vapor 40,000 surface and groundwater flow 40,000 Main Reservoirs Volume (103 cubic kiometers) 1,370,000 29,000 4,000 230 67 14 Oceans Polar ice, glaciers Groundwater Lakes, rivers Soil moisture Atmosphere (water vapor) The Hydrologic Cycle Docsity.com Other Cycles • Carbon • Nitrogen • Phosphorus Ecosystems Docsity.com