Introduction to Populations Survivorship Curves & Reproductive Strategies

Population Dynamics Why study? Study of how populations change in size, density, and age distribution in response to changes in environmental conditions Why study? Conservation Management Understand environmental changes and effects Predict future patterns

Factors that determine population size Births, deaths, immigration, emigration ( N) = [B+ I] – [D+ E] Growth rate (r) = ___N_ N0

Exponential Growth Rate Population grows faster as population increases Lag phase, acceleration phase Yields J-shaped growth curve Nt = N0ert e = 2.71 (mathematical constant)

Logistic Growth Rate Involves exponential growth rate followed by steady decrease in growth with time Population levels off at carrying capacity (K) Yields S-shaped curve

Reproductive Strategies

Reproductive strategies Trait K-selected species r-selected species Life span Long Short Reproductive age Late Early # reproductive events Few Many # offspring Parental care High Low Size of offspring Large Small Population growth rate Slow Fast Population dynamics Stable, near K Highly variable, below K

K-selected r-selected

Survivorship Curves