Population Ecology QUESTIONS: 1)What is a population? 2)What affects the size a population can get?
Population A population is a group of individuals of a single species that simultaneously occupy the same general area. Two characteristics that affect populations are ________ and _______
Population characteristics Density~ # of individuals per unit of area counts sample size estimate indirect indicators mark-recapture Dispersion~ pattern of spacing random~ unpredictable, patternless spacing (a) clumped~ patchy aggregation (b) uniform~ even spacing ( c)
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. BirthsImmigration PopuIation size Emigration Deaths Deaths and emigration remove individuals from a population.
Activity: Make a graph for a bacterial population and an elephant population
Dispatch—Get a textbook 1)Draw an exponential growth curve? What species exhibit this growth? 2)What about the environment would make an r species exhibit exponential growth? 3)Describe what a population’s carry capacity is and what it means to the population? 4)Compare and contrast density- dependent to density-independent factors? Take our calendar and tell your tablemates 3 upcoming deadlines Pick up a growth half sheet and a paper that says class set Wilderness Park 9:30 TOMORROW
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
Demography: factors that affect growth & decline of populations Birthrate (natality, fecundity)~ # of offspring produced Death rate (mortality) Age structure ~ relative number of individuals of each age Survivorship curve ~ plot of numbers still alive at each age
R vs. K survivorship curves
Population life history “strategies” r-selected (opportunistic) Short maturation & lifespan Many (small) offspring; usually 1 (early) reproduction; no parental care High death rate Ex:________ K-selected (equilibrial) Long maturation & lifespan Few (large) offspring; usually several (late) reproductions; extensive parental care Low death rate Ex :____________
Community Ecology QUESTIONS: 1) What is a community? 2) Who are the members of this community? 3) What is a food chain?
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
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.
TASK: Add a column to the right and give an example of each type of interaction Between Species
Activity: Interaction Charades I will give your group an interaction and you act it out