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Lab 10 - Demography - Student

Lab 10 - Demography - Student - BSC2011 Lab 10 Demography...

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1 Demography is the study of population numbers, including population size, density, and population growth. A population grows when birth rate exceeds death rate. Population biologists study the factors that determine demography, including resources (food, shelter, etc.), predators, diseases, and competitors. The basics of population biology apply to any taxon – from bacteria to humans to sequoia trees. Population models are equations designed to represent real-world processes in simple ways, so that we can better understand the forces that affect real populations. In this lab you will learn how two fundamental demographic models work, then build and evaluate a model of human population growth in Florida. Objectives - Understand density-independent and density-dependent population growth, and their differences. - Understand demographic principles of population growth rate and carrying capacity, and how these demographic principles affect population size. - Understand how life history (reproductive rates, survivorship, etc.) affect population growth. Methods In this lab you will use the program Populus ( http://www.cbs.umn.edu/populus/ ), which is free software for understanding population models. Populus allows us to vary terms in the models and see the results without getting tangled up in the calculations. This program has many models – we'll use only two. Other models should be quite helpful to you later in Genetics, Ecology, and Evolution courses. STARTING POPULUS The Populus icon should already be on the desktop of the computer in front of you – double- click on the icon to start the program. BSC2011 Lab 10 Demography
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BSC 2011 Lab 10 – Demography 2 DENSITY-INDEPENDENT GROWTH “Density-independent” means that a population grows without any regard to its density: no matter how crowded the population gets, and how limited resources may become per capita , the population continues to grow. Its growth rate remains the same, independent of population density. You can already see a problem: this cannot persist indefinitely in a finite world. But this model actually represents populations quite well in the short term, and the next model builds on it. Click on Model and choose Single-Species Dynamics ... Density-Independent Growth . The window that opens allows you to make and compare four versions (A, B, C, D). Two Model Types exist – Continuous and Discrete . The Continuous model uses calculus to figure population size at instantaneously small time steps. This will always yield a smooth curve. The alternative is the Discrete model, which uses simple algebra and waits one time step (generation) to figure population size. Click on View at the top, and then notice that if you click on Continuous or Discrete the program automatically switches between lambda ( ) for discrete
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Lab 10 - Demography - Student - BSC2011 Lab 10 Demography...

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