BIO 373 1st Edition Lecture 12 Outline of Last Lecture I Populations a Consequences of exponential growth b Life tables i Cohort life table ii Static life table iii Growth patterns 1 Rapid zero negative Outline of Current Lecture I Influences on Population Size a Weather b Intraspecific competition c Density dependent factors II Logistic Growth a Carrying capacity b Compare to exponential growth III Simple and complex population dynamics a Exponential and logistic growth b Population fluctuations Current Lecture Influences on Population Size Weather o Density independent factors Drought flood Intraspecific Competition o Density dependent factors As competition in females increases birth rates of females decreases 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 Negative correlation Less resources for female to give offspring As egg density increases mortality rate increases Increasing population size increasing mortality Lack of resources Decrease in resources As population density increases competition increases in general Density dependent factors o Vegetation Competition for light as e resource o Predation Competition for food source o Parasitism Increased population density when increased parasitism o Population regulation Density dependent factors cause population to increase when density is low and decrease when density is high Logistic Growth carrying capacity o B births d deaths N population density K carrying capacity o How many individuals can a site support with available resources o Initially logistic growth is similar to exponential o Eventually a population that grows logistically will level off at carrying capacity Compare logistic to exponential o Logistic growth is a downward curve when graphed as dN dt and population density Peak is at half of carrying capacity o Exponential growth is positive linear o Comparing per capita growth rate we assume birth and death rate are affected linearly by density dependence in logistic growth and we assume birth and death rate are constant in exponential growth Simple and Complex Population Dynamics Exponential and logistic growth o Example birds went from Africa to South America and began growing exponentially This was because conditions and resources were optimal In Florida now they are growing logistically because they are reaching their carrying capacity Population fluctuations o Sometimes increase or decrease precipitously in just a few days How population growth changes occur in nature Can be because of changes in upwelling temperature salinity etc o Above and below max sustainable population size o Fluctuation occurs within general growth patterns Within the general trend of exponential or logistic growth there are fluctuations in growth o Can be caused by outbreaks or peaks and declines within population cycles Maybe temperature affected organisms metabolism or resources o Delayed density dependence Logistic equation is modified to include time lags
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