The Study of Ecology2Ecologyis the study of the interactions living things have with each other and with their environment.Ecology versus environmentalism.Ecologists work on many levels of the biological sciences from molecules to ecosystemsThe ecological sciences are heavily intertwined by basic evolutionary principles
Ecology and Evolution: A very tight partnershipEcology: Considers the proximal goals of life (an individual’s survival and reproduction).Evolution: Considers the ultimate goals of the species (persistence).These two elements are inextricably interconnected.Both must be considered to really understand why a species is the way it is (its phenotype)3
Ecologists work in one or more levels4There are five scales of life that concern ecology:Organism: the unit organismPopulation: group of organisms of the same species living in one locationCommunity: populations of different species living in one locationEcosystem: the physical (abiotic) and biological (biotic)components of a habitatthe biosphere: all locations on Earth where life exists
5Levels within ecology Figure 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) and extrinsic factors (such as food availability or predators).When studying changes in population size, we refer to ‘N’ (population size), or more precisely, ∆N/∆t (change in population 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) and emigration.For a population that is closed (nobody in, nobody out) only births and deaths affect the population size at any time.The graph below shows three linear (arithmetic) models of population growth.NTimeb>db=db<d3 possible situations regarding ∆N/∆t
Arithmetic and Exponential Growth8An arithmetical increaseoccurs when, over a given interval of time, an unvarying number of new units is added to a population.An exponential increaseoccurs when the number of new units added to a population is proportional to the number of units that exists….percentgrowth.
9Arithmetic and Exponential Growth25,000256,000exponential growthof water-fleapopulationarithmetic growthof car productionConsequence: Overproduction of offspring and a struggle for existence