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Half Hollow Hills High School Ms. Foglia AP Biology Chapter 52 Population Ecology AP Biology 2004-2005 Essential Questions How do we measure a population? How do populations change over time? What factors affect population density, distribution & age structure? What are the limits to growth of a population? How many humans can the Earth support? AP Biology 2004-2005 2004-2005 1 Half Hollow Hills High School Ms. Foglia AP Biology Populations Population group of individuals of same species in same general area rely on same resources interact interbreed AP Biology 2004-2005 Population Ecology Population Ecology study of populations in relation to environment environmental influences on population density & distribution, age structure, and variations in population size What environmental factors affect a population? AP Biology 2004-2005 First measure density & dispersion 2004-2005 2 Half Hollow Hills High School Ms. Foglia AP Biology Population density How do we measure how many individuals in a population? number of individuals in an area mark & recapture methods How does this work? AP Biology Difficult to count a moving target 2004-2005 Patterns of Dispersal Spacing patterns within a population Provides insight into the environmental associations & social interactions of individuals in population AP Biology 2004-2005 2004-2005 3 Half Hollow Hills High School Ms. Foglia AP Biology Clumped Pattern AP Biology (most common) 2004-2005 Uniform may result from direct Clumped patterns interactions between individuals in the population AP Biology 2004-2005 2004-2005 4 Half Hollow Hills High School Ms. Foglia AP Biology Changes to population size Adding & removing individuals from a population birth death immigration emigration AP Biology 2004-2005 Demography Factors that affect growth & decline of populations vital statistics & how they change over time Life table What does this tell you about the population? AP Biology 2004-2005 2004-2005 5 Half Hollow Hills High School Ms. Foglia AP Biology Survivorship curves Graphic representation of life table The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females. Belding ground squirrel AP Biology 2004-2005 Survivorship curves What does this tell about survival & strategy of a species AP Biology 2004-2005 2004-2005 6 Half Hollow Hills High School Ms. Foglia AP Biology Reproductive Table Fertility schedule age-specific summary of reproductive rates for females AP Biology 2004-2005 Population growth change in population = births – deaths Exponential model (ideal conditions) dN = rmaxN dt growth increasing at constant rate N = # of individuals r = rate of growth t = time period maximum rate = intrinsic rate of increase AP Biology 2004-2005 2004-2005 7 Half Hollow Hills High School Ms. Foglia AP Biology Exponential growth rate Characteristic of populations introduced to a new environment or rebounding from a catastrophe Whooping crane coming back from near extinction African elephant protected from hunting AP Biology 2004-2005 Carrying capacity Can populations continue to grow exponentially? Of course NOT! What sets limit? Carrying Capacity (K) maximum population size that environment can support with no degradation of habitat not fixed; varies with changes in resources AP Biology 2004-2005 2004-2005 8 Half Hollow Hills High School Ms. Foglia AP Biology Logistic model of growth AP Biology 2004-2005 Logistic model of growth AP Biology 2004-2005 2004-2005 9 Half Hollow Hills High School Ms. Foglia AP Biology Life history traits K-selection = density dependent r-selection = maximize reproductive success K-selection mortality constant r-selection AP Biology 2004-2005 Trade offs Number & size of offspring vs. survival of offspring or parent AP Biology 2004-2005 2004-2005 10 Half Hollow Hills High School Ms. Foglia AP Biology Parental survival The cost of larger broods to both male & female parents AP Biology 2004-2005 Regulation of population size Limiting factors density independent environmental disturbances density dependent food supply competition predators Population cycles population fluctuations Dungeness crabs ocean currents & cannibalism AP Biology 2004-2005 2004-2005 11 Half Hollow Hills High School Ms. Foglia AP Biology Limits to growth Negative feedback prevents unlimited growth Density dependent death rate rises as birth rate rises What does it mean to be density dependent or density independent? Density independent death rate or birth rate AP Biology 2004-2005 Population dynamics Complex interaction of biotic & abiotic influences Decline of Northern Pintail AP Biology 2004-2005 Loss of habitat, predation, climatic changes affecting food availability 2004-2005 12 Half Hollow Hills High School Ms. Foglia AP Biology Isle Royale studies Moose population on small island in Lake Superior starvation wolves winter loss Why so unstable? AP Biology 2004-2005 Predator – prey interactions Population cycles AP Biology 2004-2005 2004-2005 13 Half Hollow Hills High School Ms. Foglia AP Biology Human population 2005→6 billion What factors have contributed to this exponential growth pattern? 1650→500 million AP Biology 2004-2005 Human population: rate of growth Percent increase in global human population (to 2003). Dashed portion of curve indicates projected data. Sharp dip in 1960s is due mainly to a famine in China in which ~ 60 million people died. AP Biology 2004-2005 2004-2005 14 Half Hollow Hills High School Ms. Foglia AP Biology Demographic comparisons What do the data imply about population growth in these countries? AP Biology 2004-2005 Age structure Relative number of individuals of each age What do the data imply about population growth in these countries? AP Biology 2004-2005 2004-2005 15 Half Hollow Hills High School Ms. Foglia AP Biology Impact: Ecological Footprint Is the human population near carrying capacity? deficit surplus Based on land & water area appropriated to produce all resources it consumes & to absorb all wastes it generates Biologybillion? K AP = 10–15 2004-2005 2004-2005 2005 = ~6 billion 16
