Populations

Demography

Demography

• Demography is the study of processes that influence population size - it is the way we study changes brought about by births, deaths and dispersal

For Northwest Montana, Greater Yellowstone, Central Idaho

The Fundamental Equation of Ecology – Harper 1977

Δ N = B – D + I – E

Change in Number = Births – Deaths + Immigration - Emigration

John L. Harper – 1925-2009

Rearrange Fundamental Equation

Δ N = B – D + I – E

Nfuture = Nnow + B – D + I – E

Often we assume that I = E,

so no net dispersal

Common Field Grasshopper

Grasshopper – development and incomplete metamorphosis

Red Deer – Stag, Hind, Fawn

Isle of Rhum, Scotland

Red deer fawnbeing taggedfor study

Arithmetic scale Logarithmic scale

General types of survivorship curves

Human management of species may change survivorship curves

A – fish mortality in typicalpopulation

B – fish takenby fishing

PopulationPyramidFor FranceJan. 1, 1967

Changes in population of Japan over time

Changes in population of Canada from 1971-2006