BCOR 12 1st Edition Lecture 21 Outline of Last Lecture I Anthropocene epic II Sustainability III The Scope of Ecology IV Population Ecology V Growth Models Outline of Current Lecture I Exponential Growth Model II Logistic Growth Model III Life History Traits IV Correlating Life History Traits with Population Density V Human Population Current Lecture Exponential Growth Model All populations have the potential to grow exponentially when resources are abundant Formula for exponential growth model dN r N dt 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 immigration Logistic 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 predators o Nutrients available o Water o Suitable nesting sites o Food o Etc Formula for logistic growth model K N K dN rN dt K N N Fraction of K that is still available for growth For r value o r 0 increasing population size o r 0 decreasing population over time o r 0 stable population o All of these are true for both exponential and logistic growth models K is often hard to quantify and is often a good estimate Life History Traits Life history the traits that affect an organism s schedule of reproduction and survival Examples 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 dying o 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 offspring II Likelihood of adult survival to reproduce again 1 and 2 LOW survival semelparous 1 and 2 HIGH survival iteroparous Correlating 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 in population density Increase densities cause population growth rates to decline by affecting vital rates demographics Examples that affect population density I Competition for limited resources II Predation III Toxic waste build up IV Intrinsic factors hormones etc V Territoriality VI 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 selected Human Population Our population is no longer growing exponentially but it is still increasing rapidly Annual percent increase of 75 million people year