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Transcript
The Niche American oystercatcher prying limpet off a horseshoe crab The Niche • ecological niche - the way in which an organism interacts with all of the biotic and abiotic factors in its environment - often described as how the organism makes its living, its functional role, but includes the habitat it occupies Niches in European seed-eating birds Common redpoll Greenfinch Linnet Hawfinch Precursors to theory of the niche: Law of the Minimum • The distribution of a species will be controlled by that environmental factor for which the organism has the narrowest range of adaptability or control. - Carl Sprengel 1828 Precursors to theory of the niche: Shelford’s law of tolerance • The distribution of a species is controlled by the environmental factor for which the species has the narrowest tolerance. G. Evelyn Hutchinson age 18 Hutchinson’s Niche Definitions • The fundamental niche - the set of resources and conditions that permits the survival and reproduction of an organism - many resources and conditions interact to form the niche. • The realized niche - the portion of the fundamental niche actually occupied by the species when restricted by other organisms - restricted by competition, predation, parasites, disease. - Hutchinson 1958 Fundamental vs. Realized Niche N-dimensional niche Key point – two species cannot have identical niche Populations Populations • Population - a group of organisms of the same species which have the potential to interbreed – or a population is a group of organisms of the same species occupying a particular place at a particular time • Populations have a number of properties which are not possessed by individual organisms this is because a population is the sum of many organisms interacting Starling Murmuration http://vimeo.com/31158841 Density and Distribution Prairie Dog Distributions Properties dealing with changes in population size • Natality - may think of this as births, but includes more than just birth - hatching, germination, fission • Natality includes idea of fecundity - number of offspring produced per unit time - we are most concerned with realized fecundity - actual number of survivors • Mortality - death rate - its converse is survivorship mortality looks at how many die per unit time, survivorship at how many don't die per unit time • Longevity examines life-span of individuals - again we are most interested in realized longevity, not potential longevity • Immigration - individuals moving into a population • Emigration - individuals leaving a population Changes in human longevity - life expectancy at birth Typical animal life spans What is an individual? • unitary organism - individuals are highly determinate in form and while growing pass through predictable (innately determined) sequences of life history stages • modular organisms - zygote develops into unit, or module, which produces more modules thus producing an organism with a variable number of modules, whose development is unpredictable and strongly influenced by environmental factors A classic unitary organism A classic modular organism Bryozoan colony More classic modular organisms Genets and Ramets • ramet - a module with the potential for a separate existence • genet - the "genetic individual"; the collection of all modules derived from a single zygote A single Aspen clone Posidonia oceanica – Neptune grass Sampling to collect population data Census - most basic sampling - count and determine age of all individuals in population, count again later Several ways to subsample and estimate population size: 1. Determine total area in which population occurs, count all individuals in small plots, multiply average number in plots to get total, repeat at later dates works best for sessile organisms 2. Mark-recapture methods 3. Catch per unit effort 4. Miscellaneous methods – traps, counts of fecal pellets, counts of vocalizations, feeding damage on plants, radar counts, roadside sightings, fur or pelt records, roadkill Quadrat Sampling Mark recapture of Cicadas Catch per unit effort – Pacific Threadfin Beetles feeding on Viburnum Beetle damage on Viburnum Bird migration data – typical altitude – from radar Bird migration radar map Skylark Metapopulations • A metapopulation is a series of small, separate populations united together by dispersal Metapopulation Dynamics Metapopulations of Bay Checkerspot Butterfly Bay Checkerspot Jasper Ridge Aphids and Epilobium Habitat fragmentation in Amazonia