population growth & regulation - wou
TRANSCRIPT
Population Growth & Regulation• What is Ecology• Populations• Estimating population size• Changes in population Density• Exponential growth• Logistic growth• Density independent regulation• Density dependent regulation• Population Cycles• R and K life history strategies
What is Ecology?
• Ecology is the study of interrelationships of organisms and their environment.
• Levels of Ecology--• Biomes• Ecosystem• Community• Population• Physiological• Individuals
PopulationsEstimating population size
• Population Density• (#s/ area or volume)• Two methods• Quadrat method• Set up transect• Rectangular quadrats• Count #’s for each species
Desert
Mark-Recapture
• Capture and mark individuals
• Recapture• Count number of
marked individuals that were recaptured
N = number marked X total captured# marked recaptures
Changes in population Density
• Birth• Immigration• Death• Emigration
• Use rates• b= (# births/1000)• d= (# deaths/1000• r= (b-d)
• ∆N/∆t = r No
• N = No ert
• Doubling Time = ln 2/r
• ln 2 = .693
Exponential growth
Logistic growth• ∆N/∆t = r No• Add (K-N/K)
• ∆N/∆t = r No (K-N/K)
• K= carrying capacity• Maximum sustainable
population• Can vary year to year
due to environmental conditions
Logistic growth
Regulation of Populations
• Density independent regulation
• Physical factors• Freezes• Volcanos• Tsunami
Before and After
Density dependent regulation
• Decreased fecundity• Decreased survivorship
Regulation
• Due to:• Resource limitation• Space, food, competition, predation,
disease
Population Cycles
Population Cycles
Boom and bust cycles: overexploitation
R and K life history strategies
• Trade off between survival and reproduction• Cannot maximize both• Leads to r or k selection
Life History Trade Off
Life History
• K Strategy
• Larger offspring• Fewer offspring• Live longer• Reproduce many
times (iteroparity), Late
• Some parental care
• R strategy
• Smaller offspring• Larger #’s• Shorter lifespan• Reproduce once
(semelparity), early• No parental care