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Semester 1

Population and Community Ecology 3 (BILG09009)







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Equivalent of the courses listed above

Course Summary

This course explores the interactions between organisms, the dynamics of populations and the environment. It deals with animal, plant and pathogenic organisms, and the structuring and function of communities and aims to develop both a quantitative and qualitative understanding of interactions between organisms and their consequences. The course consists of about 20 lectures and several extended practicals lasting two weeks.

Course Description

Population ecology is the study of how populations of plants, animals, and other organisms change over time and space and interact with their environment. The course is broken down into three parts:Population BiologySpecies InteractionsCommunity EcologyWe start at the simplest level: how environmental factors influence the growth of a single species population. We then add further complexity by examining how interactions between species affect their growth. Finally, we study the interactions of whole groups of species that make up communities.Populations are groups of organisms of the same species living in the same area at the same time. They are described by characteristics that include:- population size: the number of individuals in the population- population density: how many individuals are in a particular area- population growth: how the size of the population is changing over time.If population growth is just one of many population characteristics, what makes studying it so important?First, studying how and why populations grow (or shrink) helps scientists make better predictions about future changes in population sizes and growth rates. This is essential for answering questions in areas such as biodiversity conservation (e.g., the polar bear population is declining, but how quickly, and when will it be so small that the population is at risk for extinction?) and human population growth (e.g., how fast will the human population grow, and what does that mean for climate change, resource use, and biodiversity?).Studying population growth also helps scientists understand what causes changes in population sizes and growth rates. For example, fisheries scientists know that some salmon populations are declining, but do not necessarily know why. Are salmon populations declining because they have been overfished by humans? Has salmon habitat disappeared? Have ocean temperatures changed causing fewer salmon to survive to maturity? Or, maybe even more likely, is it a combination of these things? If scientists do not understand what is causing the declines, it is much more difficult for them to do anything about it. Learning what is probably not affecting a population can be as informative as learning what is.Finally, studying population growth gives scientists insight into how organisms interact with each other and with their environments. This is especially meaningful when considering the potential impacts of climate change and other changes in environmental factors (how will populations respond to changing temperatures? To drought? Will one population prosper after another declines?).A community is a group of interacting species that inhabit a particular location at a particular time. Community ecologists study the number of species in a particular location and ask why the number of species changes over time. They also study communities in different locations, and ask why the number of species differs with location. How does the depth of a lake influence the complexity of the community living within it? Why do some places contain more species than others?Community ecology seeks to answer these and other questions about communities. An ecological community is a group of actually or potentially interacting species living in the same location. Communities are bound together by a shared environment and a network of influence each species has on the other. Community ecology is an expanding and rich subfield of ecology. Ecologists investigate the factors that influence biodiversity, community structure, and the distribution and abundance of species. These factors include interactions with the abiotic world and the diverse array of interactions that occur between species. Species interactions, including competition, predation, herbivory, parasitism and mutualisms, are the basis for most of the research in community ecology. Questions of interest include: What are the feeding relationships among species? Who competes with whom and for what resources? Does the presence of some species benefit others? Food webs are a graphical depiction of the interconnections among species based on feeding relationships, and are a core concept of the field. The role of keystone species in communities is another important tenet, and one of the best-known ideas in community ecology. Keystone species are those whose presence or absence profoundly affects other species in the community, disproportionately to its abundance. A central feature of Population and Community Ecology is the use of mathematical models for describing and understanding how populations and communities change. The course therefore introduces some simple models, derived from first principles. We then demonstrate how they help us in our understanding, particularly when they break down thereby forcing us to consider possible alternative explanations.Computer modelling is also an important tool for population biologists in forecasting population numbers (for example fish stocks, or species re-introductions). The first practical introduces simple computer models of populations facing extinction and examines what conservation efforts might alleviate the risk of extinction. A report will be written about this practical and assessed.Communities are strongly influenced by their physical environment. Before attempting to unravel the mechanisms that might underlie differences among communities, we must first find ways to describe and compare communities, both quantitatively and qualitatively. The fantastic communities of micro-organisms that live on bog mosses of the genus Sphagnum are a good model system in which to learn about these techniques. The second practical introduces measures of species diversity, and how to collect data to calculate them. A report will be written about this practical and assessed.

Assessment Information

Written Exam 0%, Coursework 100%, Practical Exam 0%

Additional Assessment Information

Three open-book class tests, following each of the three blocks of teaching.Two reports on material from each of the two practicals.

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