Presentation on theme: "Overview: Counting Sheep Soay sheep were introduced to Hirta Island in 1932 Opportunity to study changes in population on isolated island with abundant."— Presentation transcript:
Number of generations Population growth begins slowing here. Exponential growth Logistic growth Population size (N) ,000 1,500 1, K = 1,500 dN dt = 1.0N dN dt = 1.0N 1,500 – N 1,500 () Figure 53.9 Population growth predicted by the logistic model.
Figure Time (days) (a) A Paramecium population in the lab (b) A Daphnia population in the lab Number of Paramecium/mL Number of Daphnia/50 mL 1, In a constant environment lacking competitors and predators, how well do these populations fit the logistic growth model?
When population density is low, b > m. As a result, the population grows until the density reaches Q. When population density is high, m > b, and the population shrinks until the density reaches Q. Equilibrium density (Q) Density-independent death rate (m) Density-dependent birth rate (b) Population density Birth or death rate per capita Figure Determining equilibrium for population density.
Figure Population size % of young sheep producing lambs Decreased reproduction at high population densities.
Figure Topsoil Bacteria EXPERIMENT Dictyostelium amoebas Dictyostelium discoideum slug 200 m Immigration / Emigration – Dictyostelium amoebas can emigrate and forage better than individual amoebas How does food availability affect emigration and foraging in a cellular slime mold? ` Dictyostelium movement
Aland Islands ˚ EUROPE Occupied patch Unoccupied patch 5 km Figure Metapopulations – groups of populations linked by immigration and emigration Glanville fritillary
Figure Percent of population Rapid growth Afghanistan Slow growth United States No growth Italy Male Female Age –84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 Age –84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0– Age-structure pyramids for the human population of three countries (2009).
Indus- trialized countries Less indus- trialized countries Infant mortality (deaths per 1,000 births) Life expectancy (years) Figure Infant Mortality and Life Expectancy