BCOR 12 1st Edition Lecture 21Outline of Last Lecture I. Anthropocene epicII. SustainabilityIII. The Scope of EcologyIV. Population EcologyV. Growth ModelsOutline of Current Lecture I. Exponential Growth ModelII. Logistic Growth ModelIII. Life History TraitsIV. Correlating Life History Traits with Population DensityV. Human PopulationCurrent LectureExponential Growth Model- All populations have the potential to grow exponentially when resources are abundant- Formula for exponential growth model:dNdt=r (N )d = change r = (birth rate/capita) – death(rate/capita)r = growth rate for the species*Does not take in effect of emigrants or immigrants*Could still see exponential growth with emigration and immigrationLogistic Growth Model- Incorporates the carrying capacity of populations- Carry capacity (K) – maximum number of individuals that can be supported by the available resources- Varies over time and space depending on the abundance of limiting resources. Examples:These 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.o Refuge (ability to hide) from predatorso Nutrients availableo Watero Suitable nesting siteso Foodo Etc. - Formula for logistic growth model:K −NKdNdt=rN ¿)(K −N )/ N = Fraction of K that is still available for growth- For r value:o r>0 = increasing population sizeo r<0 decreasing population over timeo r = 0 stable populationo All of these are true for both exponential and logistic growth models- K is often hard to quantify and is often a good estimateLife History Traits- Life history – the traits that affect an organism’s schedule of reproduction and survivalExamples:- When does reproduction begin?- How does organism reproduce?- How many offspring are produced?o Semelparous – a lot of offspring are produced and organisms only reproduces once during lifetime before dyingo Iteroparous – repeated reproduction over many years (only reproduce a few offspring at a time)- The evolution of the mode of reproduction (semel- or iteroparous) is based on:I. Survival of offspringII. Likelihood of adult survival to reproduce again1 and 2 = LOW survival = semelparous1 and 2 = HIGH survival = iteroparousCorrelating Life History Traits with Population Density- K-selection – selection for life history traits that are sensitive to population density (density-dependent)o Seen in populations at a density nearing the carrying capacity Example: mature trees in an old growth forest- Density-dependent – any population characteristic that varies according to an increase inpopulation density- Increase densities cause population growth rates to decline by affecting vital rates (demographics)Examples that affect population density:I. Competition for limited resourcesII. PredationIII. Toxic waste build-upIV. Intrinsic factors (hormones, etc.)V. TerritorialityVI. Disease- r-selection – selection for life history traits that maximize reproductive success in uncrowded environments (density independent)o Seen in populations that are below K or individuals face little competition Example: often found in disturbed habitats- Density-independent – any population characteristic that is not affected by population density- Stable populations are at or around K-capacity so they are K-selectedHuman Population- Our population is no longer growing exponentially but it is still increasing rapidly- Annual percent increase of 75 million