Principles of Population Ecology Population ecologists ask: 1) How many are in the population? 2) Are its numbers increasing / decreasing? 3) What is its pattern of reproduction? 4) What is its pattern of mortality? Significance of understanding this? Manage domestic and wild populations Manage pests Save Endangered Species Understand our own population changes

Principles of Population Ecology How Do Populations Change in Size? On a global scale (closed system):

Principles of Population Ecology How Do Populations Change in Size? On a local scale (open system):

Principles of Population Ecology How Do Populations Change in Size? Global scale: Death rate Growth rate r = b – d Birth rate

Principles of Population Ecology How Do Populations Change in Size? Local scale: Death rate Growth rate Emigration rate r = (b – d) + (i – e) Birth rate Immigration rate Rule of 70: 70/Growth Rate% = Doubling Time

J-shaped curve (exponential growth) Biotic Potential Maximum Population Growth- under ideal conditions = intrinsic rate of increase J-shaped curve (exponential growth)

Carrying Capacity Environmental Resistance- Exponential growth cannot occur forever. What factors prevent it from doing so? S-shaped curve (logistic growth)

Principles of Population Ecology Overshooting the carrying capacity can lead to a population crash. Positive & Negative Feedback Loops

Population Crash Population 1910= 26 / 1935= 2K / crash / 1945=8

Reproductive Strategies Life History Strategies r-selected K-selected vs. high growth rate slow growth rate small body size large body size early maturity late maturity short life span long life span large broods small broods little / no parental care high parental care Which are we? How do we apply this knowledge?

Survivorship & Reproduction

Density Dependent Factors Factors that influence population growth when its density is high. Predation, competition, disease, parasites, food availability.

Locust

Lemmings

Factors that Affect Population Size Density-Dependence and Boom-or-Bust Population Cycles Predator birth timing?

Predatory Prey Dynamics Wolves Established 1949 - Moose 1900 approx. 1980’s parvovirous hits wolves 1995 & 96 harsh winters and overgrazing Tick numbers increase with warm spring & fall Isle Royal southern limit of Moose

Ticks

Density-Independent Factors: Regardless of population density, influences population growth. Weather, fire, earthquakes, etc…