Biol 301 1st Edition Lecture 3 Outline of Last Lecture I. Distribution of populationsII. Population characteristicsIII. Quantifying IndividualsIV. Dispersal LimitationsOutline of Current Lecture I. DemographyII. Population growthIII. Age structureCurrent LectureDemography – - Demography – the study of (the structure and growth of) populations- Populations increase due to births and immigration- Populations decrease due to deaths and emigration- ΔN= Births + Immigration – Death - EmigrationPopulation growth- Populations grow by multiplication in proportion to their size- Humans are continuous breeders but most organisms are not and breed only at certain times of the year- Two models that show population growno Geometric growth model – discrete time intervals when a population reproduces Results in seasonal patterns of population increase and decrease N(t+1)=N(t) λ N(t+1) = number of individuals after 1 time unit N(t) = population size at time t λ = ratio of population size at any time to the population size 1 time unit earlier it is the per capita growth rate/ finite rate of increase for multiple time intervals - N(t) = N(0) l to Exponential growth – time is treated as continuousThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. A populations has a smooth curve of population increase as a function of time Nt = N0ert Nt = number of individuals after t time units N0 = initial population size r = exponential growth rate (instantaneous rate of increase) e = base of the natural logs (~ 2.72) Growth rates can be converted, which means they can represent the same data: l = er loge(l) = rAge Structure – - Age structure pyramids with broad bases indicate a growing population- Pyramids with narrow bases indicate a declining population- Pyramids with straight sides indicate a stable population- Life tables – tables that contain class-specific survival and fecundity datao Summary of survival and fecundityo Model population growth and dynamics Additions or Removals from populationso Females only (paternity problem)o Number surviving to next age class = (nx) x (sx)o Number of new offspring produced = (nx) x (sx) x (bx) x = age interval—arbitrary, but should be consistent sx = survival—survival from age class x to x+1 lx = survivorship—survival to age x bx = fecundity—number of offspring per adult at age xo Stable age distribution: when the age structure of a population does not change over time; occurs when survival and fecundity of each age class stays constant over
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