populations. population - a group of organisms of the same species which have the potential to...
Post on 19-Dec-2015
220 views
TRANSCRIPT
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 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
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
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: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, 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
Aphids and Epilobium
Habitat fragmentation in Amazonia
Demography
Demography
• Demography is the study of processes that influence population size - it is the way we study changes brought about by births, deaths and dispersal
For Northwest Montana, Greater Yellowstone, Central Idaho
The Fundamental Equation of Ecology – Harper 1977
Δ N = B – D + I – E
Change in Number = Births – Deaths + Immigration - Emigration
John L. Harper – 1925-2009
Rearrange Fundamental Equation
Δ N = B – D + I – E
Nfuture = Nnow + B – D + I – E
Common Field Grasshopper