12 Population Ecology QUESTIONS: What is a population? What affects the size a population can get?
13 PopulationA population is a group of individuals of a single species that simultaneously occupy the same general area.Two characteristics that affect populations are ________ and _______
14 Population characteristics Density~ # of individuals per unit of area•counts •sample size estimate•indirect indicators•mark-recaptureDispersion~ pattern of spacing•random~ unpredictable, patternless spacing (a)•clumped~ patchy aggregation (b)•uniform~ even spacing (c)
15 Density is the result of a dynamic interplay Between processes that add individuals to a population and those that remove individuals from it
16 Births and immigration add individuals to a population. PopuIation sizeEmigrationDeathsDeaths and emigration remove individuals from a population.
17 Activity:Make a graph for a bacterial population and an elephant population
20 Dispatch—Get a textbook Draw an exponential growth curve? What species exhibit this growth?What about the environment would make an r species exhibit exponential growth?Describe what a population’s carry capacity is and what it means to the population?Compare and contrast density- dependent to density-independent factors?Take our calendar and tell your tablemates 3 upcoming deadlinesPick up a growth half sheet and a paper that says class setWilderness Park 9:30 TOMORROW
21 Population Growth Models Exponential model (blue) • idealized population in an unlimited environment (J-curve); r-selected species (r=per capita growth rate)Logistic model (red) •carrying capacity (K): maximum population size that a particular environment can support (S-curve); K-selected species
22 Demography: factors that affect growth & decline of populations Birthrate (natality, fecundity)~ # of offspring producedDeath rate (mortality)Age structure~ relative number of individuals of each ageSurvivorship curve~ plot of numbers still alive at each age
24 Population life history “strategies” r-selected (opportunistic)Short maturation & lifespanMany (small) offspring; usually 1 (early) reproduction; no parental careHigh death rateEx:________K-selected (equilibrial)Long maturation & lifespanFew (large) offspring; usually several (late) reproductions; extensive parental careLow death rateEx:____________
25 Population limiting factors Density-dependent factors•competition•predation•stress/crowding•waste accumulationDensity-independent factors •weather/climateperiodic disturbances
26 Community Ecology QUESTIONS: 1) What is a community? 2) Who are the members of this community?3) What is a food chain?
27 Differences in Community structure Community~ an assemblage of populations living close enough together for potential interaction. Many different ______.Communities differ dramatically in their species richness (number of species) & relative abundance of different species
28 How can we account for the species found together as members of a community? 2 Hypotheses:•Individualistic~ all the species just happened to live in the same area b/c they all had similar abiotic requirements. Example they all needed same temperature, rainfall, soil type which is why they live in the same habitat.•Interactive~ all the species are locked into association by mandatory biotic interactions. Species are found together b/c they have formed relationships +, - and o.
29 Between SpeciesTASK: Add a column to the right and give an example of each type of interaction
30 Activity: Interaction Charades I will give your group an interaction and you act it out