Population Ecology: Principles, Growth, and Sustainability, Slides of Biology

Download Population Ecology: Principles, Growth, and Sustainability and more Slides Biology in PDF only on Docsity! Population Ecology Chapter 45 Docsity.com Population Ecology Certain ecological principles govern the growth and sustainability of all populations--including human populations Docsity.com Population • A group of individuals of the same species occupying a given area • Can be described by demographics – Vital statistics such as size, density, distribution, and age structure 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 Figure 45.2 Page 808 Docsity.com Assumptions in Capture-Recapture • Marking has no effect on mortality • Marking has no effect on likelihood to being captured • There is no immigration or emigration between sampling times Docsity.com Changes in Population Size • Immigration adds individuals • Emigration subtracts individuals • Births add individuals • Deaths subtract individuals Docsity.com Zero Population Growth • 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 Exponential Growth Equation G = rN • G is population growth per unit time • r is net reproduction per individual per unit time • N is 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 Figure 45.4 Page 810 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 Logistic Growth Equation G = rmax N (K-N/K) • G = population growth per unit time • rmax = maximum population growth rate per unit time • N = number of individuals • K = carrying capacity Docsity.com Logistic Growth • As size of the population increases, rate of reproduction decreases • When the population reaches carrying capacity, population growth ceases Docsity.com Overshooting Capacity • Population may temporarily increase above carrying capacity • Overshoot is usually followed by a crash; dramatic increase in deaths Figure 45.6 Page 812 Reindeer on St. Matthew’s Island Docsity.com Life History Patterns • Patterns of timing of reproduction and survivorship • Vary among species • Summarized in survivorship curves and life tables 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 Predation and Life History • Guppy populations vary in life history characteristics and morphology • Differences have genetic basis • Variation seems to be result of directional selection by predators Docsity.com Future Growth • Exponential growth cannot continue forever • Breakthroughs in technology may further increase carrying capacity • Eventually, density-dependent factors will slow growth Docsity.com Fertility Rates • Worldwide, average annual rate of increase is 1.26% • Total fertility rate (TFR) is average number of children born to a woman • Highest in developing countries, lowest in developed countries Docsity.com Population Momentum • Lowering fertility rates cannot immediately slow population growth rate • Why? There are already many future parents alive • If every couple had just two children, population would still keep growing for another 60 years Docsity.com Population Sizes in 2001 Asia 3.7 billion Europe 727 million Africa 816 million Latin America 525 million North America 316 million Oceania 31 million 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