5 Limiting factors of population Growth Availability of food and waterInvasion of parasites, pathogens, or diseaseOver-crowdingSudden Climate changesPollution of air, soil and waterIf we do not take steps to control population it is likely one of these factors will forcibly reduce our population for us!!
6 Humans Avoid Limiting Factors by… Importing resourcesImproving sanitation and medicineExpanding habitatIncreasing capacity in existing habitatsIncreasing in agricultural technology
7 Key Terms Population: number of persons Population change: a change (increase or decrease) in the number of persons (per year)Growth rates: rate of change (per year) includes births, deaths and immigration, and emigration
8 Crude Birth RateCrude Birth Rate (CBR)= number of births per populationExample: US Births = 3,999,386 and the total population is 307,645,076 people(Births / Total Population) x 1000
9 Crude Death RateCrude Death Rate (CDR)= number of deaths per populationExample: US Deaths = 2,468,435 and the total population is 307,645,076 people(Deaths/ Total Population) x 1000
10 Natural Increase Rate (NIR) Rate of Natural Increase (RNI) Rate Natural Increase is % growth rate based only on birth and death(Totally ignores immigration and emigration)RNI = (crude birth rate – crude death rate)Example: The CBR of USA is 13.0 and the CDR is Calculate the RNI of USA
11 FertilityGeneral Fertility-(# live births / female reproductive population (15-44) x 1000Example: US Births = 3,999,386 and female population ages is 62,071,000
12 Fertility ContinuedReplacement Fertility: Number of children adults need to have to replace themselvesMEDC ~ 2.1LEDC ~ 2.3 +TFR (total fertility rate) =number of children born to a woman during her reproductive years (or life time)USA TFR is 2.06Mali TFR is 7.38 !
16 Doubling Time Number of years in which a population doubles its size Doubling time can be approximated using growth rates and the rule of 70Doubling time (T) = ___70_____% growth rateCalculate Doubling Time Belowrate: 1.4% doubling time = 50 yearsrate: 2.0% doubling time = ______ yearsrate: 0.5% doubling time= _______ yearsrate: -0.5% doubling time = _______years
17 Growth Rate Human Population Growth Per Year = 1.4% LEDC (least economically developed country)=1.7%MEDC (more economically developed country) = 1.0%
19 Factors affecting fertility Rates UrbanizationImportance of children in workforceCost of raising a childEducation/Employment for womenAverage age of marriageAvailability of abortionAvailability of birth controlReligious beliefs, traditions andculture
20 Determining Future populations Use Ne(rt) formulaN= Current populatione= constant …r = growth rate as a decimal!!! (Divide by 100!)t = time in yearsExample: 2010 data reports that a population of 2,350,000 has a growth rate of 1.2%. What will the population be in 2025?
21 Carrying CapacityThe maximum population that can be sustainably supported without running out of resources.
23 Characteristics of MEDC/LEDC MEDC’sLEDC’sindustrializedlittle or no industryhigh GDP (gross domestic product)low GDPrelatively rich populationprovide raw materials but few processed or manufactured goodsaccess to education and health carelimited access to education and health carehigh resource use per capitafewer resources consumed per personlow population growth ratesmost have high population growth rates
24 What is a Population Pyramid? Graphic device: bar graphShows the age and gender composition of a regionHorizontal axis: gendermale: left-hand female: right-handabsolute number of people or %Vertical axis: age5-year or 10-year age groupsThree age population categoriesPre Reproductive- (0-14)Reproductive- (15-44)Post Reproductive- (45 +)
29 Stages of Demographic Transition Model Pre-industrial(Stage 1)LEDC(Stage 2)Wealthier LEDC(Stage 3)MEDC (Stage 4)MEDC(Stage 5)Birth rateHighDecliningLowVery lowDeath rateModerateLife expectShortMediumLongPop’l growthSlowRapidSlowingStableShrinking
30 Reason for changes in the DTM Birth rates, death rates and growth rates systematically change through time as societies change:Modernize, urbanizeGain access to new technologyBirths, deaths, migrationFertility rates play huge role
31 Stage 1 High birth rates, high death rates, low growth rates Stage for much of human history, traditional societiesPractically no country today
32 Stage 2 High birth rates, declining death rates, rising growth rates Improvements in sanitation (water) and medicineEurope during Industrial RevolutionLEDC countries since the 1950’sMuch of Africa today, some countries of Asia (Afghanistan, Nepal)
33 Stage 3Continued decline of death rates, declining birth rates, growth rates decline from high to lower levelsChange in behavior: adaptation to lower death rate, in particular infant mortality rateEconomic change: urbanization (incentive to have fewer children)Mexico today
34 Stage 4 & 5Stage 4: low birth rates, low death rates, low growth ratesUnited States todayStage 5: low birth rates, rising death rates, declining growth rates (if birth rates drop below death rates: negative growth rates)Western Europe, Japan
35 Population Pyramid and Demographic Transition Stage 2: wide base
36 Population Pyramid and Demographic Transition stage 3: wide middle
37 Population Pyramid and Demographic Transition stage 4: slender
38 Population Pyramid and Demographic Transition stage 5: narrow base
45 Models for Predicting Population growth Computer simulations:Can be highly accurate with many variablesCant include unforeseen events (i.e. natural disaster, terrorist strike, warfare)?Statistical and/or demographic tablesInclude actual field measurements based on past trends.Past trends may not always predict future trends.How large/representative are the sample populations?Age/sex pyramids (see above)Population curvesMathematical extrapolation from graphs based on real dataLess complex than computer models