BIO 311D 1st Edition Lecture 35Outline of Last Lecture I. CompetitionII. Ecological Niches and Natural SelectionIII. Character DisplacementIV. PredationV. Species DiversityVI. Diversity and Community StabilityVII. Tropic StructureVIII. Food WebsOutline of Current Lecture I. Life history traits are products of natural selectionII. Evolution and Life History DiversityIII. “Trade-offs” and Life HistoriesIV. Overview: Discovering EcologyV. The Scope of Ecological ResearchVI. Global EcologyVII. Landscape EcologyVIII. Ecosystem EcologyIX. Earth’s climate varies by latitude and season and is changing rapidlyCurrent Lecture• The logistic model fits few real populations but is useful for estimating possible growth• Conservation biologists can use the model to estimate the critical size below which populations may become extinctLife history traits are products of natural selection• An organism’s life history comprises the traits that affect its schedule of reproduction and survival– The age at which reproduction begins– How often the organism reproduces– How many offspring are produced during each reproductive cycle• Life history traits are evolutionary outcomes reflected in the development, physiology, and behavior of an organismEvolution and Life History Diversity• Species that exhibit semelparity, or big-bang reproduction, reproduce once and die• Species that exhibit iteroparity, or repeated reproduction, produce offspring repeatedly• Highly variable or unpredictable environments likely favor big-bang reproduction, while dependable environments may favor repeated reproduction“Trade-offs” and Life Histories• Organisms have finite resources, which may lead to trade-offs between survival and reproduction– For example, there is a trade-off between survival and paternal care in European kestrels• Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce• Other types of plants produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established• K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density• r-selection, or density-independent selection, selects for life history traits that maximize reproduction• The concepts of K-selection and r-selection are oversimplifications but have stimulated alternative hypotheses of life history evolutionOverview: Discovering Ecology• Ecology is the scientific study of the interactions between organisms and the environment• These interactions determine the distribution of organisms and their abundance• Modern ecology includes observation and experimentation• The rediscovery of the nearly extinct harlequin toad in Costa Rica raises many ecological questions• What environmental factors limit their geographic distribution?• What factors (food, pathogens) affect population size?The Scope of Ecological Research• Ecologists work at levels ranging from individual organisms to the planetGlobal Ecology• The biosphere is the global ecosystem, the sum of all the planet’s ecosystems• Global ecology examines the influence of energy and materials on organisms across the biosphereLandscape EcologyA landscape or seascape is a mosaic of connected ecosystemsLandscape ecology focuses on the exchanges of energy, materials, and organisms across multiple ecosystemsEcosystem EcologyAn ecosystem is the community of organisms in an area and the physical factors with which they interactEcosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic componentsCommunity Ecology• A community is a group of populations of different species in an area• Community ecology deals with the whole array of interacting species in a communityPopulation Ecology• A population is a group of individuals of the same species living in an area• Population ecology focuses on factors affecting population size over timeOrganismal Ecology• Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges• Organismal ecology includes physiological, evolutionary, and behavioral ecologyEarth’s climate varies by latitude and season and is changing rapidly• The long-term prevailing weather conditions in an area constitute its climate• Four major abiotic components of climate are temperature, precipitation, sunlight, and wind• Macroclimate consists of patterns on the global, regional, and landscape level• Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen
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