BESC 201 1st Edition Lecture 8 Outline of Last Lecture I Biodiversity Outline of Current Lecture II Levels of Ecological Organization III Population Ecology Current Lecture Chapter 3 Lecture 8 Levels of Ecological Organization Ecology the study of interactions among organizations and between organisms and their environments We study ecology at several levels Level Organism relationships between the organism and its physical environment Level Population Ecology dynamics of population change and the factors that affect the distribution and abundance of its members Level Community Ecology patterns of species diversity and interactions among species Level Ecosystem flow of energy and nutrients and living nonliving components Habitat niche and specialization are key concepts on ecology Habitat the specific environment where an organism lives Habitat selection mobile organisms actually selecting habitats from a range of options Habitats are scale dependent tiny soil mite vs elephant Every species assess habitat differently because every species has different needs These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Niche a species use of resources and its functional role in a community Multidimensional summary of everything it does Specialists narrow breadth and have very specific requirements Generalists broad tolerances and use a wide array of resources Population Ecology Several characteristics help us predict population dynamics Population size the number of individual organisms present at a given time Population density the number of individuals in a population per unit area Large organisms have low population densities because each individual requires many resources and land to live High population densities lead to competition and transmission of disease and vulnerability to predator attacks Population distribution the spatial arrangement of organisms in an area Three types random uniform and clumped Random distribution located haphazardly in no pattern trees Uniform distribution individuals evenly spaced they hold territory plants in a desert Clumped distribution most common organisms arranged according to availability of resources schools of fish Sex Ratio proportion of males to females Can influence whether the population will increase or decrease over time Age structure the relative numbers if organisms of each age within a population Can predict population growth decline by evaluating reproductive potential Populations may grow shrink or remain stable Demographers scientists who study human populations Population growth determined by four factors 1 Births within population natality 2 Deaths within population mortality 3 Immigration arrival from outside 4 Emigration departure from inside Growth rate birth rate immigration death rate emigration Answer tells net change in population size per 1 000 individuals per year Calculate to a percentage by growth rate x 100 Unregulated populations increase by exponential growth Exponential growth when a population increases by a fixed percentage each year Shown by J curves in population growth charts will keep growing until they meet constraints Limiting factors restrain population growth Limiting factors physical chemical ad biological attributes of environment that restrain growth Carrying capacity interaction of limiting factors that make op the maximum population size Logistic growth curve curve that rises sharply then levels off from limiting factors Density dependent factors influence rises and falls with population density finding a mate Density independent factors limiting factors whose influence is not affected by population density temperature Carrying capacities can change Overcoming limiting factors via technology for example can increase carrying capacity Reproductive strategies vary among species Biotic potential ability to produce offspring small fish with thousands of eggs vs a whale K selected populations stabilize over time near carrying capacity have few young and take time raising them elephants humans R selected high biotic potential and produce as much as possible population fluctuates greatly insects K and R selected species are the two extremes many species fall somewhere in between Changes in populations influence the composition of communities Changes in climate can cause population fluctuations and disease outbreaks that affect the whole community not just one species Conservation can help address biodiversity loss Ecotourism people visiting natural areas putting money into troubles nation s economy