5Population dispersion spatial patternsspaced -- may indicate competing individualsclumped -- may indicate social patterns or resource distribution
6A random dispersionIs one in which the position of each individual is independent of other individuals(c) Random. Dandelions grow from windblown seeds that land at random and later germinate.
7A uniform dispersionIs one in which individuals are evenly distributedMay be influenced by social interactions such as territorialityFigure 52.3b(b) Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors.
8A clumped dispersion Is one in which individuals aggregate in patches May be influenced by resource availability and behaviorFigure 52.3a(a) Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory.
9Density is the result of a dynamic interplay between processes Density is the result of a dynamic interplay between processes that add individuals to a population and those that remove individuals from it.Births and immigration add individuals to a population.BirthsImmigrationPopuIation sizeEmigrationDeathsDeaths and emigration remove individuals from a population.
10The life table of Belding’s ground squirrels Reveals many things about this population
11A survivorship curveIs a graphic way of representing the data in a life table…Figure 52.41000100101Number of survivors (log scale)2468Age (years)MalesFemalesThe survivorship curve for Belding’s ground squirrelsShows that the death rate is relatively constant
12patterns in age structure Populationpatterns in age structure
17r- vs K-selection r-selection K-selection r is the rate of a population’s increaseK is a population’s carrying capacityDisturbance Common, irregular Rarer, more regularMortality Variable, unpredictable Constant, predictableCompetition Low or variable High, constantPop. size Variable, below K Rel. constant, near KConsequence High r Good competitors
18Small sizeRapid growthEarly reproductionMany, small offspringLarge sizeSlow growthLate reproductionFew, large offspring
19A. Body size and rOn average, small organisms have higher rates of per capita increase and more variable populations than large organisms.
20K vs. r selection: extremes in parental care Humpback whalesSea urchins
22When there are no limits, populations grow faster, Population Growth Geometric growth vs. exponential growth vs logistic growth.Bottom line:When there are no limits, populations grow faster,and FASTERand FASTER!Invasive Cordgrass (Spartina) in Willapa Bay
23The Simple Case: Geometric Growth Constant reproduction rateNon-overlapping generations (like annual plants, insects)Also, discrete breeding seasons (like birds, trees, bears)Suppose the initial population size is 1 individual. This indivual reproduces once & dies, leaving 2 offspring. How many if this continues?
24Exponential GrowthAssumes continuous breeding life history strategy and overlapping generations.