The Study of Ecology2Ecologyis the study of the interactionsliving things have with each other and withtheir environment.Ecology versus environmentalism.Ecologists work on many levels of thebiological sciences from molecules toecosystemsThe ecological sciences are heavilyintertwined by basic evolutionary principles
Ecology and Evolution:A very tightpartnershipEcology:Considers theproximal goalsoflife (an individual’s survival andreproduction).Evolution:Considers theultimate goalsofthe species (persistence).These two elements are inextricablyinterconnected.Both must be considered to really understandwhy a species is the way it is (its phenotype)3
Ecologists work in one or more levels4There are five scales of life that concernecology:Organism:the unit organismPopulation:group of organisms of thesame species living in one locationCommunity:populations of differentspecies living in one locationEcosystem:the physical (abiotic) andbiological (biotic)components of a habitatthebiosphere:all locations on Earth wherelife exists
5Levels within ecologyFigure 33.2organism(sea lion)population(colony)community(giant kelp forest)ecosystem(Southern Californiacoast)biosphere(Earth)
Let’s first look at Populations6Populations experience changes in their size over time.Intrinsicfactors (such as reproductive rates) andextrinsicfactors (such as food availability or predators).When studying changes in population size, we refer to ‘N’(population size), or more precisely, ∆N/∆t (change inpopulation size over a change in time).AKA, dN/dt
Positive and negative population growth7Two general factors increase a population size:births (b)and immigrations.Two factors decrease population size:deaths (d) andemigration.For a population that is closed (nobody in, nobody out)only births and deaths affect the population size at anytime.The graph below shows three linear (arithmetic) modelsof population growth.NTimeb>db=db<d3 possible situations regarding ∆N/∆t
Arithmetic and Exponential Growth8Anarithmetical increaseoccurs when,over a given interval of time, anunvarying number of new units is addedto a population.Anexponential increaseoccurs whenthe number of new units added to apopulation is proportional to the numberof units that exists….percentgrowth.
9Arithmetic and Exponential Growth25,000256,000exponential growthof water-fleapopulationarithmetic growthof car productionConsequence: Overproduction of offspring and a struggle for existence